JP4239444B2 - Nitride semiconductor laser diode - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a nitride semiconductor device, and more particularly to a nitride semiconductor light emitting device such as a laser diode (LD) device and a light emitting diode (LED) device and a light receiving device such as a solar cell, and more particularly to a nitride semiconductor. The present invention relates to a light emitting device.
[0002]
[Prior art]
Nitride semiconductors can have a band gap energy ranging from 1.95 to 6.0 eV depending on their composition, so that they can be used as materials for semiconductor light emitting devices such as light emitting diode (LED) devices and laser diode (LD) devices. It has attracted attention from the past. Recently, high-intensity blue LED devices and green LED devices have been put into practical use using this nitride semiconductor material. These LED devices have a double heterostructure with a pn junction, and both outputs exceed 1 mW.
[0003]
A conventional LED device basically has a double hetero structure in which an active layer made of InGaN is sandwiched between an n-type and p-type clad layer made of AlGaN. An n-type contact layer made of GaN is formed on the n-type cladding layer, and a p-type contact layer made of GaN is formed on the p-type cladding layer. This laminated structure is provided on a substrate made of sapphire, for example.
[0004]
The LD device may basically have the same structure as the LED device. However, particularly in the case of an LD device, a separate confinement structure in which light and carriers are confined separately is often used. A nitride semiconductor separation and confinement type LD device is disclosed in, for example, Japanese Patent Laid-Open No. 6-21511. This publication includes an InGaN active layer sandwiched between two light guide layers, one of which is made of n-type GaN and the other of which is made of p-type GaN, and a carrier made of n-type AlGaN on the n-type light guide layer. A light-emitting device having a separate confinement structure in which a confinement layer is formed and another carrier confinement layer made of p-type AlGaN is formed on the p-type light guide layer is disclosed.
[0005]
By the way, in an ordinary semiconductor device having a double hetero structure, a first cladding layer having a band gap energy larger than that of the active layer is provided in contact with the active layer, and the first cladding layer is in contact with the first cladding layer. A second cladding layer having a larger band gap energy than that of the other cladding layer is provided. This is because electrons and holes are efficiently injected into the active layer according to the energy level.
[0006]
Similarly, in the case of a nitride semiconductor LD device, a cladding layer such as a light guide layer and a carrier confinement layer (light confinement layer) is sequentially formed so that the band gap energy gradually increases in contact with the active layer ( For example, see the above publication).
[0007]
[Problems to be solved by the invention]
However, it has been found that conventional nitride semiconductor devices, particularly LD devices, having an indium-containing active layer have low luminous efficiency in the above structure. In particular, it has been found that when the device temperature rises as the current applied to the device is increased, the luminous efficiency is drastically reduced.
[0008]
Accordingly, an object of the present invention is to provide a nitride semiconductor device having an active layer containing a nitride semiconductor containing indium and having high luminous efficiency. Another object of the present invention is to provide a nitride semiconductor device in which a decrease in luminous efficiency is small even when the device temperature rises.
[0009]
[Means for Solving the Problems]
  In order to solve the above problems, the present invention provides:It has a multiple quantum well structure in which well layers made of InGaN and barrier layers made of InGaN having a larger band gap than the well layers are alternately stacked.Active layer andp-side contact layerIn contact with the active layerProvided,In_cAl_dGa_1-cdN (0 ≦ c, 0 <d, c + d ≦ 1)500 AngstromThe following first nitride semiconductor layer and In_eAl_fGa_1-efA third nitride semiconductor layer made of N (0 ≦ e, 0 <f, e + f ≦ 1) and having a thickness of 0.01 μm or more and 2 μm or less, and the first nitride semiconductor layer and the third nitride In between the semiconductor layer, In_XGa_1-XFrom N (0 ≦ X ≦ 1)And having a smaller band gap energy than the first nitride semiconductor layer and a thickness of 0.01 μm to 5 μm.A second nitride semiconductor layer, wherein the third nitride semiconductor layer has a larger band gap energy than the second nitride semiconductor layer.And the uppermost layer of the active layer formed in contact with the second nitride semiconductor layer and in contact with the first nitride semiconductor layer is a barrier layer made of InGaN.
[0010]
In the nitride semiconductor device of the present invention, the active layer is sandwiched between a layer structure that should ultimately contact the positive electrode and a layer structure that should ultimately contact the negative electrode. In the following description, the side on which the layer structure that should ultimately contact the positive electrode is referred to as the p side, and the side on which the layer structure that ultimately contacts the negative electrode is formed may be referred to as the n side. .
[0011]
Therefore, the nitride semiconductor layer structure can be provided on the p side or the n side of the active layer, or on both the p side and the n side. The first nitride semiconductor layer preferably has a thickness sufficiently thin that carriers can tunnel, and more specifically, preferably has a thickness of 0.1 μm or less. In general, the first nitride semiconductor layer preferably has a thickness of at least 10 angstroms.
[0012]
According to the second aspect of the present invention, in the second aspect, the first clad layer made of an n-type nitride semiconductor; provided on the first clad layer and made of a nitride semiconductor containing indium and gallium and having a thickness of 70 angstroms or less. An active layer having a quantum well structure including at least one well layer provided on the base layer in a lattice-mismatched state with respect to the base layer, wherein the well layer includes a plurality of well layers An active layer including an indium rich region and an indium poor region; and a nitride semiconductor comprising a second cladding layer provided on the active layer and made of a nitride semiconductor doped with an acceptor impurity Provide a device.
[0013]
In the present invention, when broadly referred to as a nitride semiconductor, a nitride of a Group 3 element of the periodic table, more specifically, the formula In_xAl_yGa_1-xyIt refers to a nitride semiconductor represented by N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1).
[0014]
The inventors of the present invention have studied the decrease in light emission efficiency with increasing temperature, particularly in a nitride semiconductor device having an active layer containing indium. As a result, the main cause of the decrease in luminous efficiency is that nitride semiconductors containing indium, especially InGaN, have a property that they are less likely to grow than nitride semiconductors containing aluminum or gallium nitride (GaN). I found out. That is, the decomposition temperature of InN and GaN constituting InGaN is remarkably different, and InGaN tends to phase-separate into InN and GaN during growth, and an active layer having a uniform composition can be obtained by increasing the indium content. Hateful. Therefore, in a conventional nitride semiconductor having an InGaN active layer, the indium content tends to be kept low.
[0015]
When the GaN light guide layer is formed in contact with the InGaN active layer having a low indium content, the band offset between the active layer and the light guide layer is extremely small. This will be described with reference to FIG. 6, which is a diagram showing an energy band corresponding to a conventional nitride semiconductor light emitting device. As shown in FIG. 6, in the conventional nitride semiconductor device, the band gap energy of the light guide layer (GaN) directly sandwiching the InGaN active layer is not so large as compared with the band gap energy of the active layer (InGaN). (Because the In content in InGaN is low, the InGaN composition approximates the GaN composition). For this reason, when the temperature of the device rises as the current value applied to the semiconductor device increases, the electrons and holes injected from the n layer and the p layer into the active layer recombine due to the influence of the thermal energy, respectively. Before emitting light (hν), electrons and holes overflow the active layer to the guide layer (GaN) opposite to the injection side, that is, electrons are in the p-type light guide layer, holes are It reaches even the n-type light guide layer. As a result, the light emission efficiency is low in the conventional structure, and particularly when the temperature rises, the efficiency decreases.
[0016]
Therefore, in the nitride semiconductor device of the present invention, two first layers (a first p-side layer and a first layer formed between and in contact with an active layer including a nitride semiconductor containing indium) are interposed. The n-side layer is formed of a nitride semiconductor having a band gap energy larger than that of the active layer. These first layers only have to have a band gap energy larger than that of the active layer, and preferably the two first layers have a band larger by 0.01 to 4.05 eV than the active layer. Has gap energy. Due to the presence of the first layer having such a large band gap energy, electrons or holes injected into the active layer do not overflow the active layer. Each first layer preferably has a band gap energy smaller than the band gap energy of the first layer, preferably in contact with the first layer, but preferably larger than the band gap energy of the active layer. Two second layers (second p-side layer and second n-side layer) formed of a nitride semiconductor are provided. These second layers only need to have a band gap energy smaller than that of the first layer, and preferably 0.01 to 4.05 eV smaller than the first band gap energy. Have Furthermore, on each second layer, preferably in contact therewith, two third layers (third layers) formed of a nitride semiconductor having a band gap energy larger than that of the second layer. a p-side layer and a third n-side layer). These third layers only have to have a band gap energy larger than that of the second layer, and preferably 0.01 to 4.05 eV higher than the band gap energy of the second layer. Has a large band gap energy. Thus, electrons or holes injected from the third layer side are efficiently injected into the second layer having a smaller band gap energy, but the first layer has a large band gap energy, so that it is active. Injection into the layer tends to be blocked by the first layer. Therefore, in the present invention, the first layer is formed so thin that electrons or holes can penetrate through the first layer by a tunnel effect (tunneling). Thus, electrons or holes are efficiently injected from the third layer to the active layer. Thus, in the device of the present invention, electrons and holes are efficiently injected from the third layer into the active layer, and electrons or holes are blocked by the first layer opposite to the injection side. Even if the device temperature rises, the active layer does not overflow. Regarding the band gap energy of the nitride semiconductor, the band gap energy of AlN is 6.0 eV, the band gap energy of GaN is 3.4 eV, and the band gap energy of InN is 1.95 eV.
[0017]
As is clear from the above description, in the present invention, if the three-layer structure including the first layer, the second layer, and the third layer is provided on one surface of the active layer, electrons or One of the holes is prevented from overflowing the active layer. Most preferably, this three-layer structure is provided on both sides (p side and n side) of the active layer.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described with reference to FIGS. Throughout these drawings, the same elements and members are denoted by the same reference numerals. FIG. 1 is a schematic cross-sectional view showing one structure of an LD device according to the first embodiment of the present invention. In this LD device, the three-layer structure of the present invention is provided on the p side.
[0019]
1 includes an n-type contact layer 13, an n-type carrier confinement layer (light confinement layer) 14, an n-type light guide layer 15, an active layer 16, an active layer on a substrate 11 via a buffer layer 12. A first p-side nitride semiconductor layer 101 having a larger bandgap energy than the layer 16, a second p-side nitride semiconductor layer 102 having a smaller bandgap energy than the first p-side nitride semiconductor layer, A nitride semiconductor multilayer structure including a third p-side nitride semiconductor layer 103 having a band gap larger than that of the p-side nitride semiconductor layer 102 and the p-type contact layer 17 is provided. On the p-type contact layer 17, a current confinement layer 18 having a contact hole 18a is provided. A negative electrode 19 is provided on the exposed surface of the n-type contact layer 13, and a positive electrode 20 is provided on the current confinement layer 20. The positive electrode 20 is in contact with the p-type contact layer 17 through the contact hole 18 a of the current confinement layer 18.
[0020]
The substrate 11 is made of spinel (MgAl₂O₄), Sapphire (Al₂O₃Conventional materials proposed for growing nitride semiconductors such as SiC (including 6H, 4H, 3C), ZnS, ZnO, GaAs, GaN, etc. can be used. .
[0021]
The buffer layer 12 can be formed of AlN, GaN, AlGaN, or the like, and can be formed at a temperature of 900 ° C. or less and a thickness of several tens of angstroms to several hundreds of angstroms. The buffer layer 12 is formed to alleviate the lattice constant mismatch between the substrate 11 and the nitride semiconductor layer formed thereon. Therefore, when using a substrate lattice-matched with the nitride semiconductor, a substrate having a lattice constant close to that of the nitride semiconductor, etc., it may be omitted depending on the method of growing the nitride semiconductor.
[0022]
The n-type contact layer 13 is formed of a nitride semiconductor, particularly GaN, In_aGa_1-aN (0 <a <1) is preferable. (In this specification, In_aGa_1-aN (0 <a <1) or a nitride semiconductor represented by a similar expression may be simply referred to as InGaN). In particular, when the n-type contact layer 13 is formed of Si-doped GaN, an n-type layer with a high carrier concentration is obtained, and a preferable ohmic contact with the negative electrode 19 is obtained, thereby reducing the threshold current of the laser element. be able to. Although there is no restriction | limiting in particular in the thickness of the n-type contact layer 13, Usually, it can form in thickness of 0.1 micrometer-5 micrometers.
[0023]
The negative electrode 19 formed on the surface exposed by the etching of the n-type contact layer 13 can obtain a preferable ohmic contact with the n-type contact layer 13, so that Al, Ti, W, Cu, Zn, Sn, In, etc. It is preferable to form with a metal or an alloy thereof.
[0024]
The n-type carrier confinement layer 14 and the n-type light guide layer 15 formed on the layer 14 are each formed of an n-type nitride semiconductor. In the embodiment shown in FIG. 1, the n-type light guide layer 15 has a larger band gap energy than the band gap energy of the active layer 16, and the n-type carrier confinement layer 14 has the band gap energy of the n-type light guide layer 15. Has a larger bandgap energy. The n-type carrier confinement layer 14 is usually formed with a thickness of 0.1 μm to 1 μm, and the n-type light guide layer 15 is preferably formed with a thickness of 100 Å to 1 μm.
[0025]
The active layer 16 formed on the n-type light guide layer 15 has a quantum well structure (that is, a single quantum well structure or a multiple quantum well structure). And an indium-containing nitride semiconductor having a band gap smaller than the band gap of both the first p-side nitride semiconductor layer 101, that is, In_dAl_eGa_1-deIt has a well layer made of N (0 <d ≦ 1, 0 ≦ e ≦ 1, 0 <d + e ≦ 1). Preferably, the well layer is a ternary mixed crystal In._fGa_1-fN (0 <f <1). Since the ternary mixed crystal InGaN provides a layer having better crystallinity than the quaternary mixed crystal, the light emission output is improved.
[0026]
Among them, the active layer 16 has a multiple quantum well structure (minimum three-layer structure) in which a well layer made of InGaN and a barrier layer made of a nitride semiconductor having a band gap energy larger than that of the well layer are alternately stacked. ) Is particularly preferable. In the present invention, the multiple quantum well structure has a well layer as a lowermost layer directly provided on an n-type layer such as the n-type light guide layer 15 and a p-type layer such as a first p-side nitride semiconductor 101 described below. Or the first p-side nitride semiconductor as a bottom layer directly provided on an n-type layer such as the n-type light guide layer 15 or the like. A structure having a barrier layer as an uppermost layer in direct contact with a p-type layer such as the layer 101 may be used. The nitride semiconductor that forms the barrier layer includes GaN, AlGaN, and the like. However, the barrier layer is made of ternary mixed crystal In as well as the well layer._{f '}Ga_{1-f '}It is particularly preferable to form N (0 <f ′ <1, where f ′ <f). When the active layer 16 has a multi-quantum well structure in which InGaN layers having different band gap energies are stacked as described above, the indium mole fraction of the active layer 16 is changed or the first or third n-side or p-side nitridation described below is performed. By changing the aluminum mole fraction of the physical semiconductor layer, a high-power LD device having a wavelength of about 365 nm to 660 nm can be realized by light emission between quantum levels. Furthermore, when an InGaN barrier layer is stacked on the well layer, the InGaN barrier layer has a softer crystal than AlGaN, so that the thickness of, for example, an AlGaN layer as a cladding layer formed thereon is increased without causing cracks. As a result, excellent laser oscillation can be realized.
[0027]
In the multiple quantum well structure, it is particularly desirable that the well layer has a thickness of 70 angstroms or less and the barrier layer has a thickness of 150 angstroms or less. On the other hand, it is particularly desirable that the active layer having a single quantum well structure constituted by one quantum well layer has a thickness of 70 angstroms or less. The lower limit of the thickness of both the well layer and the barrier layer is preferably 5 angstroms.
[0028]
The active layer 16 may be one that is not doped with impurities (non-doped), or one that is doped with impurities (acceptor impurities and / or donor impurities) in the well layer and / or the barrier layer. Particularly preferred active layer 16 is a non-doped active layer and a silicon or germanium doped active layer, and among the active layers doped with impurities, a particularly preferred one is a silicon doped active layer. Particularly, when the active layer is doped with silicon, the threshold current tends to decrease in the LD device. In addition, silicon doping is performed during the growth of a nitride semiconductor to form an active layer, for example, as a source gas, for example, an organic silicon gas such as tetraethylsilane, a silicon hydride gas such as silane, or a silicon halide gas such as silicon tetrachloride. Etc. can be added.
[0029]
The first p-side nitride semiconductor layer 101 provided in contact with the active layer 16 is formed of a nitride semiconductor having a band gap energy larger than that of the active layer 16 (more precisely, its well layer). . Particularly preferably, the first nitride semiconductor layer is a nitride semiconductor containing Al, that is, In._gAl_hGa_1-g-hN (0 ≦ g ≦ 1, 0 <h ≦ 1, 0 <g + h ≦ 1), particularly preferably ternary mixed crystal Al_jGa_1-jN (0 <j <1). (In this specification, Al_jGa_1-jN (0 <j <1) or a nitride semiconductor represented by a similar expression may be simply referred to as AlGaN).
[0030]
The first p-side nitride semiconductor layer 101 is preferably i-type or p-type. In particular, AlGaN is easy to obtain a p-type with a high carrier concentration, and when formed in contact with the active layer 16 including a well layer containing InGaN, an element with high light output can be obtained.
[0031]
In the present invention, to make the nitride semiconductor (including the nitride semiconductor of the active layer) p-type, it is necessary to dope an acceptor impurity such as Mg, Zn, C, Be, Ca, Ba during crystal growth. Obtained by. Acceptor impurity concentration is 1 × 10¹⁷~ 1x10²²/ Cm³It is preferable that In particular, when the acceptor impurity is magnesium, the concentration is 1 × 10¹⁸~ 1x10²⁰/ Cm³, Especially 1 × 10¹⁹~ 1x10²⁰/ Cm³Is particularly preferred. In any case, in order to obtain a p-layer with a high carrier concentration, it is more desirable to anneal (heat treat) at 400 ° C. or higher in an inert gas atmosphere after doping acceptor impurities. Annealing is usually performed in the case of Mg-doped p-type AlGaN at 1 × 10¹⁷~ 1x10¹⁹/ Cm³The carrier concentration can be obtained. In order to obtain an i-type nitride semiconductor, for example, Al_jGa_1-jBy growing a nitride semiconductor having a value of j of 0.5 or more in N, an i-type nitride semiconductor can be obtained without doping an acceptor impurity. In addition, an i-type nitride semiconductor is an acceptor in which a p-type nitride semiconductor layer is doped with a donor impurity sufficient to compensate its hole carrier concentration, or an n-type nitride semiconductor layer is merely compensated for its electron carrier concentration. It can also be obtained by doping impurities.
[0032]
The thickness of the first nitride semiconductor layer 101 is preferably thin enough that carriers can tunnel through the first nitride semiconductor layer 101. More specifically, the semiconductor layer 101 desirably has a thickness of 0.1 μm or less, more preferably 0.05 μm (500 angstroms) or less, and most preferably 0.03 μm (300 angstroms) or less. When the thickness of the semiconductor layer 101 is reduced in this way, cracks in the first p-side nitride semiconductor layer 101 can be prevented, and a nitride semiconductor layer with good crystallinity can be grown. Further, when the AlGaN having a larger Al ratio is formed thinner, laser oscillation is more likely. For example, Al whose j value is 0.2 or more_jGa_1-jWhen N is used, it is desirable to form the semiconductor layer 101 with a thickness of 500 angstroms or less. The lower limit of the thickness of the first p-side nitride semiconductor layer 101 is not particularly limited, but it is preferable to form the first p-side nitride semiconductor layer 101 with a thickness of 10 angstroms or more.
[0033]
The second p-side nitride semiconductor layer 102 has a band gap energy smaller than that of the first p-side nitride semiconductor layer 101 and is larger than that of the first p-side nitride semiconductor layer 101. It is located away from the active layer and is most preferably formed in contact with the first p-side nitride semiconductor layer 101 as shown in FIG. The second p-side nitride semiconductor layer 102 is preferably In_kGa_1-kN (0 ≦ k ≦ 1), particularly preferably GaN or InGaN. When the second p-side nitride semiconductor layer 102 is formed of GaN or InGaN, the second semiconductor layer 102 with good crystallinity is obtained with few cracks even when formed relatively thick. The second p-side nitride semiconductor layer 102 preferably has a thickness of 0.01 μm to 5 μm, more preferably 0.02 μm to 1 μm. In this range of thickness, for example, it can function as a preferable light guide layer. . The second p-side nitride semiconductor layer 102 contains an acceptor impurity and is preferably p-type.
[0034]
Further, the second p-side nitride semiconductor layer 102 formed of InGaN or GaN in particular also functions as a buffer layer when a third p-side nitride semiconductor layer 103 described later is grown. InGaN or GaN is softer than AlGaN. Therefore, the second p-side nitride semiconductor layer made of InGaN or GaN between the first p-side nitride semiconductor layer 101 having a larger band gap than the active layer and the third p-side nitride semiconductor layer 103. 102 is prevented from generating a crack in the third p-side nitride semiconductor layer 103, whereby the third p-side nitride semiconductor layer 103 is replaced with the first p-side nitride semiconductor layer. It can be formed thicker than 101.
[0035]
The third p-side nitride semiconductor layer 103 has a band gap energy larger than that of the second p-side nitride semiconductor layer 102 and is more active than the second p-side nitride semiconductor layer 102. Most preferably, it is formed in contact with the second p-side nitride semiconductor layer 102 as shown in FIG. The third p-side nitride semiconductor layer 103 is a nitride semiconductor containing Al, that is, In_mAl_nGa_1-mnN (0 ≦ m ≦ 1, 0 <n ≦ 1, 0 <m + n ≦ 1) is preferable, and ternary mixed crystal AlGaN is particularly preferable.
[0036]
The third p-side nitride semiconductor layer 103 is required to have a band gap energy larger than that of the second p-side nitride semiconductor layer 102. This is because the third p-side nitride semiconductor layer 103 functions as a carrier confinement layer and an optical confinement layer. The third p-side nitride semiconductor layer 103 desirably has a thickness of 0.01 μm or more and 2 μm or less, more preferably 0.05 μm or more and 1 μm or less. It can act as a good carrier confinement layer. The third p-side nitride semiconductor layer 103 contains acceptor impurities, and is preferably p-type.
[0037]
The p-type contact layer 17 formed on the third p-side nitride semiconductor layer 103 is formed of a p-type nitride semiconductor. In particular, when the p-type contact layer 103 is formed of InGaN or GaN, in particular, p-type GaN doped with Mg, a p-type layer with the highest carrier concentration is obtained, and good ohmic contact with the positive electrode is achieved. The current can be reduced.
[0038]
The positive electrode 20 is preferably formed of a metal having a relatively high work function such as Ni, Pd, Ir, Rh, Pt, Ag, Au, or an alloy thereof, in order to obtain ohmic contact.
[0039]
The current confinement layer 18 is formed of an insulating material, preferably silicon dioxide. This current confinement layer 18 can be omitted. By the way, in FIG. 1, the n-type carrier confinement layer 14 is formed on the n-type contact layer 13 via the crack prevention layer 30.
[0040]
That is, a nitride semiconductor containing aluminum has a property that cracks are likely to occur in the grown crystal when the thickness is increased. In particular, it is difficult to directly grow an n-type aluminum-containing nitride semiconductor without causing cracks on the GaN layer or the AlGaN layer. For example, an n-type nitride that needs to be formed to a thickness as thick as, for example, 0.1 μm or more like an n-type carrier confinement layer 14 on an n-type contact layer 13 formed of n-type GaN or the like includes aluminum. It is difficult to form a semiconductor, particularly AlGaN. Therefore, on the n-type contact layer 13, as a crack prevention layer 30, a nitride semiconductor containing indium, preferably In_pGa_1-pAfter forming an n-type layer made of N (0 <p ≦ 1), an n-type carrier confinement layer 14 made of an n-type aluminum-containing nitride semiconductor is formed. The presence of the crack prevention layer 30 allows the n-type carrier confinement layer 14 to grow to a desired thickness (for example, 0.1 μm or more) without generating cracks. The crack prevention layer 30 preferably has a thickness of 100 Å or more and 0.5 μm or less. It should be noted that the crack preventing layer 30 has the same effect even if it is inside the n-type contact layer 13.
[0041]
FIG. 2 is a cross-sectional view schematically showing a nitride semiconductor LD device according to the second embodiment of the present invention. The same reference numerals as those in FIG. 1 denote the same members. Referring to FIG. 2, an n-type contact layer 13, a crack prevention layer 30, a third n-side nitride semiconductor layer 203, and a second n-side nitride semiconductor layer are disposed on the substrate 11 via the buffer layer 12. 202, a first n-side nitride semiconductor layer 201, an active layer 16, a p-type light guide layer 31, a p-type carrier confinement layer (light confinement layer) 32, a p-type contact layer 17, and a current confinement layer 18 are sequentially formed. ing. A negative electrode 19 is electrically connected to the n-type contact layer 13, and a positive electrode 20 is electrically connected to the p-type contact layer 17.
[0042]
In the LD device shown in FIG. 2, the first n-side nitride semiconductor layer 201, the second n-side nitride semiconductor layer 202, and the third n-side nitride semiconductor layer 203 are those except for the conductivity type. The corresponding first p-side nitride semiconductor layer 101 and second p-side nitride semiconductor respectively described with respect to FIG. 1 in terms of the band gap energy, the nitride semiconductor material constituting them and the range of their thicknesses. The first p-side nitride semiconductor layer 101, the second p-side nitride semiconductor layer 102, and the third p-side nitride semiconductor are basically the same as the layer 102 and the third p-side nitride semiconductor layer 103. The material preference and thickness preference described for the semiconductor layer 103 are also the first n-side nitride semiconductor layer 201, the second n-side nitride semiconductor layer 202, and the third n-side, respectively. Nitride semiconductor layer 203 It can be applied with.
[0043]
To repeat briefly, the first n-side nitride semiconductor layer 201 formed in contact with the active layer 16 has a larger band gap energy than the active layer 16 (more precisely, its well layer). It is formed with. The first n-side nitride semiconductor layer 201 is particularly preferably formed of a nitride semiconductor containing Al, and particularly preferably formed of ternary mixed crystal AlGaN.
[0044]
Similarly to the first p-side nitride semiconductor 101, the thickness of the first n-side nitride semiconductor layer 201 is also thin enough that carriers (electron carriers) can tunnel through the first n-side nitride semiconductor layer 201. Has a thickness. More specifically, the semiconductor layer 201 desirably has a thickness of 0.1 μm or less, more preferably 0.05 μm (500 angstroms) or less, and most preferably 0.03 μm (300 angstroms) or less. It is desirable that the first n-side nitride semiconductor layer 201 also has a thickness of 10 angstroms or more.
[0045]
The first n-side nitride semiconductor layer 201 is preferably n-type or i-type. In the present invention, an n-type nitride semiconductor (including an active layer) can also be obtained in a non-dope (state not doped with impurities), but in order to obtain a preferable n-type, Si, Ge, Sn during crystal growth are used. , S, and the like, which are obtained by doping with a donor impurity. In that case, the donor impurity is 1 × 10¹⁶~ 1x10²²/ Cm³It is preferable to dope at a concentration of In particular, silicon is 1 × 10¹⁷~ 1x10²¹/ Cm³A concentration of 1 × 10 is particularly preferred.¹⁸~ 1x10²⁰/ Cm³The concentration of is most preferred.
[0046]
The second n-side nitride semiconductor layer 202 has a band gap energy smaller than that of the first n-side nitride semiconductor layer 201 and is larger than that of the first n-side nitride semiconductor layer 201. It is located away from the active layer and is most preferably formed in contact with the first n-side nitride semiconductor layer 201 as shown in FIG. The second n-side nitride semiconductor layer 202 is preferably In_kGa_1-kN (0 ≦ k ≦ 1), particularly preferably GaN or InGaN. The second n-side nitride semiconductor layer 202 preferably has a thickness of 0.01 μm to 5 μm, more preferably 0.02 μm to 1 μm. In this range of thickness, for example, it can function as a preferable light guide layer. . The second n-side nitride semiconductor layer 202 is n-type. As described with reference to FIG. 1, the second p-side nitride semiconductor layer 102 serves as a buffer layer for growing the third p-side nitride semiconductor layer 103 formed relatively thick thereon. It is working. Similarly, the second n-side nitride semiconductor layer 202 also functions as a buffer layer when the first n-side nitride semiconductor layer 201 is grown, but the first n-side nitride semiconductor layer 201 is thin. The role as a buffer layer is not so important.
[0047]
Similarly to the third p-side nitride semiconductor layer 103, the third n-side nitride semiconductor layer 203 also functions as a carrier confinement layer and an optical confinement layer, so that the band gap energy of the second n-side nitride semiconductor layer 202 is increased. The second n-side nitride semiconductor layer has a larger bandgap energy and is more distant from the active layer 16 than the second n-side nitride semiconductor layer 202, and most preferably as shown in FIG. It is formed in contact with 202. The third n-side nitride semiconductor layer 203 is also preferably formed of a nitride semiconductor containing Al, and particularly preferably formed of ternary mixed crystal AlGaN. It is desirable that the third n-side nitride semiconductor layer 203 also has a thickness of 0.01 μm or more and 2 μm or less, more preferably 0.05 μm or more and 1 μm or less. It can act as a good carrier confinement layer and optical confinement layer. The third n-side nitride semiconductor layer 203 is n-type. The third n-side nitride semiconductor layer 203 preferably made of a nitride semiconductor containing aluminum is formed on the n-type contact layer 13 preferably made of n-type GaN via the crack prevention layer 30. Yes.
[0048]
The p-type light guide layer 31 and the p-type carrier confinement layer (light confinement layer) 32 are each formed of a p-type nitride semiconductor. The band gap energy of the p-type carrier confinement layer (light confinement layer) 32 is larger than that of the p-type light guide layer 31.
[0049]
FIG. 3 shows a nitride semiconductor LD device according to the presently most preferred embodiment in which the three-layer laminated structure of the present invention is formed on both sides (p side and n side) of the active layer. Referring to FIG. 3, an n-type contact layer 13, a crack prevention layer 30, a third n-side nitride semiconductor layer 203, and a second n-side nitride semiconductor layer are disposed on the substrate 11 via the buffer layer 12. 202, first n-side nitride semiconductor layer 201, active layer 16, first p-side nitride semiconductor layer 101, second p-side nitride semiconductor layer 102, third p-side nitride semiconductor layer 103, and A nitride semiconductor multilayer structure including the p-type contact layer 17 is provided. On the p-type contact layer 17, a current confinement layer 18 having a contact hole 18a is provided. A negative electrode 19 is provided on the exposed surface of the n-type contact layer 13, and a positive electrode 20 is provided on the current confinement layer 18. The positive electrode 20 is in contact with the p-type contact layer 17 through the contact hole 18 a of the current confinement layer 18. The elements making up the device shown in FIG. 3 are as described with respect to FIGS.
[0050]
Note that the nitride semiconductor layer constituting the nitride semiconductor device of the present invention can be preferably grown by metal organic vapor phase epitaxy (MOVPE). However, the nitride semiconductor layer can also be grown by other methods conventionally used for growing nitride semiconductors such as hydride vapor phase epitaxy (HDVPE), molecular beam vapor phase epitaxy (MBE), etc. Can do.
[0051]
FIG. 4 schematically shows an energy band of an LD device having an active layer having a multiple quantum well structure having the structure shown in FIG. As shown in FIG. 4, in the double heterostructure LD device of the present invention, the first p-side nitride semiconductor layer 101 and the first n-side are in contact with the active layer 16 including the indium-containing nitride semiconductor. A nitride semiconductor layer 201 is provided. That is, it is larger than the band gap energy of the active layer 16 (more precisely, its well layer), and more than the band gap energy of the second p-side nitride semiconductor layer 102 and the second p-side nitride semiconductor layer 202. Two first nitride semiconductor layers 101 and 201 having a large band gap energy are provided in contact with the active layer 16. Moreover, since the film thicknesses of these two first nitride semiconductor layers are set thin, these semiconductor layers 101 and 201 do not act as a barrier against carriers, and the third n-side nitride Electron carriers injected into the second n-side nitride semiconductor layer 202 from the semiconductor layer 203 side, and positive carriers injected into the second p-side nitride semiconductor layer 102 from the third p-side nitride semiconductor layer 103 side. The hole carriers can penetrate each of the first n-side nitride semiconductor layer 201 and the first p-side nitride semiconductor layer 101 by the tunnel effect, recombine efficiently in the active layer 16, and emit light (hν). To emit.
[0052]
Since the injected carriers have a large hand gap energy in the first nitride semiconductor layers 101 and 201, the carriers exceed the active layer 16 even if the temperature of the device rises or the injected current density increases. -Since it does not flow and is blocked by the first nitride semiconductor layers 101 and 201, carriers are effectively accumulated in the active layer 16 and light can be emitted efficiently. Therefore, the nitride semiconductor device of the present invention is an LD device having a low threshold current with little reduction in luminous efficiency even when the device temperature rises.
[0053]
By the way, the present inventors have studied in detail the active layer in the device of the present invention, particularly an active layer having a well layer made of a nitride semiconductor containing indium and gallium. As a result, it has been found that, for example, when InGaN is grown, the grown InGaN layer becomes non-uniform in terms of indium content depending on conditions, thus forming an indium rich region and an indium poor region. Electron carriers and hole carriers are localized in the indium-rich region thus formed, and emit light based on excitons or light emitted based on bi-excitons. That is, the indium rich region constitutes a quantum dot or a quantum box. In order for the InGaN well layer to form such a quantum dot or quantum box, the well layer is formed on the n-type semiconductor layer as in the device described with reference to FIGS. It was found that it was formed on the contained nitride semiconductor 15, 201) in a lattice-mismatched state with respect to the n-type semiconductor layer and had a thickness of 70 angstroms or less. The well layer structure is conveniently formed by forming a semiconductor layer thereon after a short time, preferably 2 to 20 seconds after it is formed. In addition, the further layer formed on the active layer which has this well layer should just contain acceptor impurities. The LD device having such a configuration has a lower threshold current than a normal quantum well laser and may have a higher characteristic temperature.
[0054]
Thus, the present invention provides a first clad layer made of an n-type nitride semiconductor; a nitride semiconductor provided on the first clad layer and made of a nitride semiconductor containing indium and gallium, and having a thickness of 70 angstroms or less, An active layer having a quantum well structure including at least one well layer provided on the underlayer in a lattice mismatched state with respect to the underlayer, wherein the well layer includes a plurality of indium rich regions and an indium pore layer. There is also provided a nitride semiconductor device comprising: an active layer including a region; and a second cladding layer formed on the active layer and made of a nitride semiconductor doped with an acceptor impurity. Here, when the underlayer is referred to, the first cladding layer itself or the first cladding such as an n-type semiconductor layer (aluminum-containing nitride semiconductors 15 and 201) as in the device described with reference to FIGS. It shall mean the barrier layer provided on the layer or the barrier layer itself. FIG. 5 is a sectional view conceptually showing this device. In FIG. 5, the active layer is shown as having a single quantum well structure for simplicity. As shown in FIG. 5, the quantum well layer (active layer) 54 formed on the first clad layer 52 made of an n-type nitride semiconductor to a thickness of 70 angstroms or less in a lattice mismatched state is, for example, as a whole. InGaN is formed of InGaN, but indium rich region 54a and indium poor region 54b are formed by causing phase separation. More specifically, indium rich regions 54a and indium poor regions 54b exist as dots or boxes, which may be 20-50 angstroms in size, and each indium rich region 54a and each indium poor region 54b is a well layer. Are arranged almost regularly alternately in the surface direction. A second cladding layer 56 made of a nitride semiconductor doped with an acceptor impurity is provided on the active layer 54.
[0055]
Of course, the active layer having the well layer constituting the quantum dot or the quantum box preferably constitutes the active layer 16 in the device described with reference to FIGS. The band gap energy of the phase separated well layer is determined by the average composition of the well layer.
[0056]
In an active layer having a well layer constituting such a quantum dot or quantum box, doping the acceptor impurity and / or donor impurity can further reduce the threshold current.
[0057]
That is, the non-uniform content of indium in the plane of one well layer means that there are InGaN regions (indium rich region and indium poor region) having different band gaps in the plane direction of the single well layer. Means. Accordingly, electrons existing in the conduction band once fall into the indium-rich region, and then recombine with holes existing in the valence band, thereby releasing hν energy. In other words, electron carriers and hole carriers are localized in the indium-rich region (phase) of the well layer, forming localized excitons, helping to lower the laser threshold current and improving the laser emission output. Let
[0058]
When such a well layer is doped with a donor impurity such as silicon and / or an acceptor impurity, an energy level at an impurity level is further formed between the conduction band and the valence band. Therefore, the electron carrier falls to the energy level of a deeper impurity level, and the hole carrier moves to the level of the p-type impurity, where the electron carrier and the hole carrier are recombined to reduce the smaller energy hν. discharge. This is believed to be that electron carriers and hole carriers are more localized, and the threshold current of the laser device is lowered by the effect of the exciton formed by further localization. As the impurity doped into the well layer, silicon and germanium are preferable, and silicon is particularly preferable. In particular, doping the silicon tends to further reduce the threshold current of the device. It should be noted that impurities such as silicon and magnesium may be doped not only in the well layer but also in the barrier layer. In the case of an active layer having a multiple quantum well structure, only one well layer or one barrier layer You may dope only.
[0059]
【Example】
Hereinafter, the present invention will be described with reference to examples.
Example 1
In this example, a nitride semiconductor LD device having the structure shown in FIG. 3 was produced.
[0060]
First, a well-cleaned spinel substrate 11 (MgAl₂O₄) Was set in the reaction vessel, and the inside of the reaction vessel was sufficiently replaced with hydrogen, and then the temperature of the substrate was raised to 1050 ° C. while flowing hydrogen to clean the substrate.
[0061]
Next, the temperature was lowered to 510 ° C., hydrogen was used as a carrier gas, ammonia and trimethyl gallium (TMG) were used as source gases, and a GaN buffer layer 12 was grown on the substrate 11 to a thickness of about 200 Å.
[0062]
After growth of the buffer layer, the temperature was raised to 1030 ° C. while stopping only the TMG flow and flowing ammonia gas. At 1030 ° C., TMG gas was added, and silane gas (SiH as a dopant gas)₄), An Si-doped n-type GaN layer was grown to a thickness of 4 μm as the n-type contact layer 13.
[0063]
Next, the temperature is lowered to 800 ° C., TMG, TMI (trimethylindium) and ammonia are used as source gases, silane gas is used as impurity gas, and Si-doped In_0.1Ga_0.9A crack preventing layer 30 made of N was grown to a thickness of 500 angstroms.
[0064]
Next, the temperature was raised to 1030 ° C., trimethylaluminum (TMA), TMG and ammonia were used as source gases, silane was used as a dopant, and Si-doped n-type Al_0.2Ga_0.8A third n-type nitride semiconductor layer 203 made of N was grown to a thickness of 0.5 μm.
[0065]
Next, the temperature was lowered to 800 ° C., only the TMA flow was stopped, and a second n-type nitride semiconductor layer 202 made of Si-doped n-type GaN was grown to a thickness of 0.2 μm. Next, the temperature is raised to 1050 ° C., TMA, TMG and ammonia are used as source gases, silane is used as a dopant, and Si-doped n-type Al_0.1Ga_0.9A first n-type nitride semiconductor layer 201 made of N was grown to a thickness of 300 Å.
[0066]
Next, the active layer 16 was grown as follows using TMG, TMI and ammonia as source gases. First, the temperature is kept at 800 ° C. and non-doped In_0.2Ga_0.8A well layer made of N was grown to a thickness of 25 Å. Next, the molar ratio of TMI is changed, and at the same temperature, non-doped In_0.01Ga_0.99A barrier layer made of N is grown to a thickness of 50 Å. This operation was repeated twice. Finally, a well layer was stacked, and a total of seven active layers having a multiple quantum well structure were grown.
[0067]
Next, the temperature was raised to 1050 ° C., and TMG, TMA, ammonia, cyclopentadienyl magnesium (Cp₂Mg) and Mg-doped p-type Al_0.1Ga_0.9A first p-type nitride semiconductor layer 101 made of N was grown to a thickness of 300 Å.
[0068]
Subsequently, at 1050 ° C., TMG, ammonia, and Cp₂Using Mg, the second p-type nitride semiconductor layer 102 made of Mg-doped p-type GaN was grown to a thickness of 0.2 μm.
[0069]
Next, at 1050 ° C., TMG, TMA, ammonia, cyclopentadienyl magnesium (Cp₂Mg) and Mg-doped p-type Al_0.2Ga_0.8A third p-type nitride semiconductor layer 103 made of N is grown to a thickness of 0.5 μm.
[0070]
Finally, a p-type contact layer 17 made of Mg-doped p-type GaN was grown at 1050 ° C. to a thickness of 0.5 μm. After the completion of all the reactions, the temperature was lowered to room temperature, the wafer was taken out of the reaction vessel, and the wafer was annealed at 700 ° C. to further reduce the resistance of the p-type layer. Next, the uppermost p-type contact layer 17 was etched in a stripe shape until the surface of the n-type contact layer 13 was exposed. After etching, a current confinement layer 18 made of silicon dioxide is formed on the surface of the p-type contact layer 17, a contact hole is formed in this, and then Ni is in contact with the p-type contact layer 17 through the current confinement layer 18. And a positive electrode 20 made of Au was formed in a stripe shape. On the other hand, the negative electrode 19 made of Ti and Al was formed in a stripe shape.
[0071]
Next, the wafer is cut into a bar shape in a direction perpendicular to the striped electrodes, and the cut surface is polished to create a parallel mirror.₂And TiO₂A dielectric multilayer film was alternately laminated. Finally, after cutting the bar in the direction parallel to the electrode to make a laser chip with a stripe size of 4 μm × 600 μm, the chip was placed on a heat sink and laser oscillation was attempted at room temperature. Under a pulse current (pulse width 10 micron) Second, duty ratio 10%), laser oscillation with an oscillation wavelength of 400 nm was confirmed, and threshold pulse current density = 2 kA / cm², T₀(Characteristic temperature) = 200K.
[0072]
Next, the LD device of the present invention was evaluated based on the temperature dependence of the threshold current density of the device. LD threshold current density J_thExp (T / T₀(However, T: Operating temperature (K), T₀: Proportional to characteristic temperature (K). That is, T₀The larger the value, the lower the threshold current density, and the LD device operates stably even at high temperatures.
[0073]
In the device of Example 1, when neither of the first nitride semiconductor layers 101 and 201 was formed, laser oscillation did not occur. In Example 1, when only one of the first nitride semiconductor layers 101 and 201 is not formed, the LD device of the present invention has Jth = 3 kA / cm.², T₀Was 100K. The LD device of Example 1 includes both Al of both the first nitride semiconductor layers 101 and 201._jGa_1-jWhen the j value of N is 0.1 (Example 1), as described above,_th= 2kA / cm², T₀= 200K, but j value is 0.2, J_th= 1.5kA / cm², T₀= 300K, j value is 0.3_th= 1.4kA / cm², T₀= 400K, indicating that the LD device of the present invention has very excellent temperature characteristics.
[0074]
Example 2
An LD device of the present invention was obtained in the same manner as in Example 1 except that the first n-side nitride semiconductor layer 201 was not grown. This LD has the same structure as the LD device shown in FIG. 1, and the n-type carrier confinement layer (light confinement layer) 14 in FIG. 1 corresponds to the third n-side nitride semiconductor layer 203, and n The type light guide layer 15 corresponds to the second n-side nitride semiconductor layer 202. This LD device has Jth = 3 kA / cm²Thus, laser oscillation with an oscillation wavelength of 400 nm was confirmed, and T0 = 100K.
[0075]
Example 3
An LD device of the present invention was obtained in the same manner as in Example 1 except that the first p-side nitride semiconductor layer 101 was not grown. This LD has the same structure as the LD device shown in FIG. 2, and the p-type carrier confinement layer (light confinement layer) 32 in FIG. 2 corresponds to the third p-side nitride semiconductor layer 103, and p The type light guide layer 31 corresponds to the second p-side nitride semiconductor layer 102. This LD device is similar to the LD of Example 2 in J_th= 3kA / cm²Confirmed laser oscillation with an oscillation wavelength of 400 nm, and T₀= 100K.
[0076]
Example 4
The active layer 16 is made of non-doped In having a thickness of 50 Å._0.2Ga_0.8A single quantum well structure made of an N well layer is used, and the first p-type nitride semiconductor layer 101 is made of Al._0.3Ga_0.7An LD device of the present invention was obtained in the same manner as in Example 2 except that it was formed of N. This LD is also J_th= 5kA / cm²Confirms laser oscillation with an oscillation wavelength of 410 nm, and T₀= 50K.
[0077]
Example 5
The second n-type nitride semiconductor layer 202 is made of Si-doped n-type In_0.01Ga_0.99The second p-type nitride semiconductor 102 is formed of N and the Mg-doped p-type In_0.01Ga_0.99An LD device was produced in the same manner as in Example 1 except that it was formed of N. This LD device exhibited exactly the same characteristics as the LD device of Example 1.
[0078]
Example 6
Each of the well layer and the barrier layer of the active layer is made of 1 × 10 5 silicon as a donor impurity.¹⁹/ Cm³An LD device of the present invention was produced in the same manner as in Example 1 except that doping was performed at a concentration of. This LD device has a threshold current approximately 5% lower than that of the LD device of Example 1, and T₀Improved by approximately 10%.
[0079]
Example 7
In the well layer and the barrier layer of the active layer, magnesium as an acceptor impurity is 1 × 10¹⁸/ Cm³An LD device of the present invention was produced in the same manner as in Example 1 except that doping was performed at a concentration of. This LD device exhibited almost the same characteristics as the LD device of Example 1.
[0080]
Example 8
Each of the well layer and the barrier layer of the active layer is made of 1 × 10 5 silicon as a donor impurity.¹⁹/ Cm³1 × 10 5 magnesium and as an acceptor impurity¹⁸/ Cm³An LD device of the present invention was produced in the same manner as in Example 1 except that doping was performed at a concentration of. This LD device exhibited almost the same characteristics as the LD device of Example 6.
[0081]
Example 9
Each non-doped In_0.2Ga_0.8An LD device was fabricated in the same manner as in Example 1 except that each barrier layer was formed after the N (average composition) well layer was formed and held for 5 seconds. In this LD device, the well layer is phase-separated into an indium rich region and an indium poor region, and the indium rich region has a composition of almost In._0.4Ga_0.6N, the composition of the indium poor region is almost In_0.02Ga_0.98It was equivalent to N. In addition, the cross-sectional TEM photograph of the well layer confirmed that indium rich regions and indium poor regions each having an average size of 30 angstroms were regularly arranged alternately in the plane direction (see FIG. 5). . The LD device fabricated in this way has a threshold current density that is approximately 30% lower than that of the LD device of Example 1, and T₀It was improved by 20%.
[0082]
Example 10
An LD device was fabricated in the same manner as in Example 9 except that each well layer was doped with silicon. This LD device is approximately 40% lower in threshold current density than the LD device of Example 1, and T₀30% improvement. In each of the above examples, the impurities whose concentration was not particularly pointed out were doped within the preferred range described above.
[0083]
In the embodiment described above, as the most preferable example, the active layer, the first nitride semiconductor layer, the second nitride semiconductor layer, and the third nitride semiconductor layer are formed in contact with each other. In the present invention, only the first nitride semiconductor layer may be formed in contact with the active layer, and between the first nitride semiconductor layer and the second nitride semiconductor layer, Another nitride semiconductor layer can be inserted between the second nitride semiconductor layer and the third nitride semiconductor layer. The concentration of doped impurities is
[0084]
【The invention's effect】
As described above, according to the present invention, a nitride semiconductor device having an active layer including a nitride semiconductor containing indium and having high luminous efficiency is provided, and the device temperature is increased. Even in this case, a nitride semiconductor device with little decrease in luminous efficiency is provided.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing an LD device according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view schematically showing an LD device according to a second embodiment of the present invention.
FIG. 3 is a cross-sectional view schematically showing an LD device according to a third aspect of the present invention.
4 is a diagram showing an energy band corresponding to the device structure shown in FIG. 3;
FIG. 5 is a cross-sectional view schematically showing an LD device according to a fourth embodiment of the present invention.
FIG. 6 is a diagram showing an energy band corresponding to a layer structure of a conventional LD device.
[Explanation of symbols]
11 ... Board
13 ... n-type contact layer
14 ... n-type carrier confinement layer
15 ... n-type light guide layer
16, 54 ... active layer
17 ... p-type contact layer
19 ... Negative electrode
20 ... Positive electrode
30 ... Crack prevention layer
52. First cladding layer
54a: Indium rich region
54b: Indium poor region
56: Second cladding layer
101. First p-side nitride semiconductor layer
102 ... Second p-side nitride semiconductor layer
103. Third p-side nitride semiconductor layer
201: first n-side nitride semiconductor layer
202 ... Second n-side nitride semiconductor layer
203 ... Third n-side nitride semiconductor layer.

Claims (6)

Between an active layer having a multiple quantum well structure in which a well layer made of InGaN and a barrier layer made of InGaN having a band gap larger than that of the well layer are alternately stacked, and a contact layer on the p side ,
Provided in contact with the active layer, and _{In c Al d Ga 1-cd} N (0 ≦ c, 0 <d, c + d ≦ 1) from become the first nitride film thickness 500 angstroms or less of the semiconductor layer,
_{In e Al f Ga 1-ef} N (0 ≦ e, 0 <f, e + f ≦ 1) from become thickness 0.01μm or more, the third nitride semiconductor layer of 2μm or less,
Between the first nitride semiconductor layer and the third nitride semiconductor _{layer, In X Ga 1-X N} (0 ≦ X ≦ 1) Tona is, smaller than the first nitride semiconductor layer A second nitride semiconductor layer having a band gap energy and a thickness of 0.01 μm to 5 μm ,
The third nitride semiconductor layer, said second band gap energy than that of the nitride semiconductor layer is rather large, and is formed in contact with the second nitride semiconductor layer,
The nitride semiconductor laser diode , wherein the uppermost layer of the active layer in contact with the first nitride semiconductor layer is a barrier layer made of InGaN . The nitride semiconductor laser diode according to claim 1 , wherein the first nitride semiconductor layer and the second nitride semiconductor layer are in contact with each other. The first nitride semiconductor layer, a nitride semiconductor laser diode according to claim 1 or 2 b value is equal to or 0.2 or more Al _b Ga _1-b N. The nitride semiconductor laser diode according to any one of claims 1 to 3, characterized in that emission of 365nm~660nm is obtained by band-to-band emission of the active layer. The third nitride semiconductor layer, the first nitride semiconductor laser diode according to any one of claims 1 to 4, characterized in that thicker than that of the nitride semiconductor layer. The first nitride semiconductor layer and / or the third nitride semiconductor layer, a nitride semiconductor laser diode according to any one of claims 1 to 5 consisting of AlGaN.

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