JP5229128B2 - Semiconductor light emitting device - Google Patents

Description

  The present invention relates to a semiconductor light emitting device, and more particularly to a semiconductor light emitting device using a nitride III-V compound semiconductor.

  In recent years, a nitride-based III-V compound semiconductor represented by gallium nitride (GaN) (hereinafter also referred to as a “GaN-based semiconductor”) has been put to practical use as a light-emitting diode (LED) using the GaN-based semiconductor. The achievement of a laser diode using this GaN-based semiconductor has attracted a great deal of attention, and applications such as light sources for optical disk devices are expected.

  A GaN semiconductor laser has, for example, a DH structure (Double Heterostructure) in which an active layer made of GaInN is sandwiched between an n-type AlGaN cladding layer and a p-type AlGaN cladding layer as a basic structure. The n-type AlGaN cladding layer and the p-type AlGaN cladding layer have a lower refractive index and a higher band gap than the active layer, and have a role of confining light generated in the active layer and a role of suppressing carrier overflow. In a GaN-based semiconductor laser having a SCH structure (Separate Confinement Heterostructure), an n-type GaN optical waveguide layer and a p-type layer are further provided between the active layer and the n-type AlGaN cladding layer and between the active layer and the p-type AlGaN cladding layer, respectively. A type GaN optical waveguide layer is provided. Many of GaN-based semiconductor lasers that have achieved continuous oscillation at room temperature so far have this AlGaN / GaN / GaInN SCH structure. Among them, in the case of the emission wavelength band of 400 nm, for example, the active layer is made of GaInN having an In composition of about 15%, and the n-type AlGaN cladding layer and the p-type AlGaN cladding layer have an Al composition of about 6-8%. It is made of AlGaN.

  However, the operating current and operating voltage of a conventional GaN-based semiconductor laser are higher than those of AlGaAs semiconductor lasers and AlGaInP-based semiconductor lasers that have already been put into practical use, which is a condition that causes practical problems.

  In order to reduce the operating current of a GaN-based semiconductor laser, it is effective to reduce the threshold current density. As a technique for realizing this, the Al composition of the n-type AlGaN cladding layer and the p-type AlGaN cladding layer is increased. Thus, a method of reducing the refractive index and increasing the band gap, increasing the light confinement rate Γ, and suppressing the carrier overflow can be considered. However, the p-type AlGaN cladding layer tends to be less likely to generate carriers as the band gap increases. Therefore, when the Al composition of the p-type AlGaN cladding layer is increased in order to reduce the threshold current density, the resistance of the p-type AlGaN cladding layer increases and the operating voltage of the device increases.

FIG. 8 is a graph showing the relationship between the Al composition of the p-type AlGaN cladding layer and the operating voltage in a conventional GaN-based semiconductor laser. The sample used for this measurement is a ridge stripe type having an AlGaN / GaN / GaInN SCH structure, the resonator length is 1 mm, and the stripe width is 3.5 μm. In FIG. 8, an operating voltage V _op indicates a voltage when the sample is pulse-driven at room temperature under the conditions of a frequency of 1 kHz, a duty ratio of 0.5%, and a current of 100 mA. FIG. 8 shows that the operating voltage V _op increases as the Al composition of the p-type AlGaN cladding layer increases. Such an increase in operating voltage not only shortens the lifetime of the device but also hinders high output of the semiconductor laser. Therefore, a GaN-based semiconductor laser capable of oscillating at a low threshold current density while suppressing an increase in operating voltage. Development is desired.

  Accordingly, an object of the present invention is to provide a semiconductor light emitting device using a nitride III-V group compound semiconductor capable of reducing the threshold current density with almost no increase in operating voltage.

In order to achieve the above object, the present invention provides:
In a semiconductor light emitting device having an active layer sandwiched between an n-type cladding layer and a p-type cladding layer, wherein the active layer, the n-type cladding layer and the p-type cladding layer are made of a nitride III-V compound semiconductor,
The p-type cladding layer is composed of two or more semiconductor layers having different band gaps, and the portion near the interface on the active layer side of the p-type cladding layer is composed of a semiconductor layer having a larger band gap than other portions. It is characterized by being.

  In the present invention, the nitride-based III-V group compound semiconductor includes at least one group III element selected from the group consisting of Ga, Al, In, B, and Tl, and at least N. Or it consists of a V group element containing P.

In the present invention, p-type cladding layer is typically from different _{B x Al y Ga z In 1} -xyz N compositions together (although, 0 ≦ x, y, z ≦ 1,0 ≦ x + y + z ≦ 1) It comprises two or more semiconductor layers.

  In the present invention, the semiconductor layer having a large band gap constituting the portion near the interface on the active layer side of the p-type cladding layer is preferably used from the viewpoint of effectively preventing the overflow of electrons to the p-type cladding layer. Is provided at a position within 100 nm from the interface on the active layer side of the p-type cladding layer, and more preferably at a position within 50 nm from the interface on the active layer side of the p-type cladding layer. The thickness of the semiconductor layer having a large band gap is preferably selected from 20 nm to 100 nm from the viewpoint of preventing electron tunneling and minimizing the increase in resistance caused by this layer.

  In the present invention, since the p-type cladding layer has a simple structure and has a high effect of preventing overflow of electrons, typically, the first semiconductor layer on the active layer side and the first semiconductor layer are formed on the p-type cladding layer. The band gap of the first semiconductor layer is made larger than the band gap of the second semiconductor layer. At this time, the band gap of the first semiconductor layer is formed such that a barrier high enough to suppress the overflow of electrons is formed in the conduction band of the p-type cladding layer from the viewpoint of functioning this layer as a barrier layer. Chosen to be. On the other hand, the band gap of the second semiconductor layer having a small band gap has a resistance value as low as possible in order to suppress an increase in operating voltage while maintaining a refractive index that does not significantly deteriorate vertical optical confinement. So chosen.

  According to the semiconductor light emitting device of the present invention configured as described above, the p-type cladding layer is composed of two or more semiconductor layers having different band gaps, and the portion near the interface on the active layer side of the p-type cladding layer is By being composed of a semiconductor layer having a larger band gap than other parts, overflow of carriers (electrons) from the n-type clad layer side to the p-type clad layer side is prevented, and light emission of the injected current occurs. Since the component of the leakage current that does not contribute to is reduced, the threshold current density can be reduced. At this time, the other part of the p-type cladding layer can be constituted by a semiconductor layer having a smaller band gap than the semiconductor layer constituting the part in the vicinity of the interface on the active layer side. Can be suppressed. Thereby, in the semiconductor light emitting device using the nitride-based III-V group compound semiconductor, the threshold current density can be reduced without substantially increasing the operating voltage.

  According to the semiconductor light emitting device of the present invention, the p-type cladding layer is composed of two or more semiconductor layers having different band gaps, and the portion near the interface on the active layer side of the p-type cladding layer has a band compared to other portions. By being composed of a semiconductor layer having a large gap, overflow of carriers (electrons) from the n-type cladding layer side to the p-type cladding layer side is prevented, and a leakage current component that does not contribute to light emission in the injected current Is reduced, the threshold current density can be reduced. At this time, the other part of the p-type cladding layer can be constituted by a semiconductor layer having a smaller band gap than the semiconductor layer constituting the part in the vicinity of the interface on the active layer side. Can be suppressed. As a result, a semiconductor light emitting device using a nitride III-V group compound semiconductor capable of reducing the threshold current density without substantially increasing the operating voltage can be obtained. In addition, since the increase in operating voltage is suppressed, the life of the element can be extended and the output can be increased.

1 is a cross-sectional view of a GaN semiconductor laser according to a first embodiment of the present invention. 1 is a cross-sectional view showing a detailed structure of a p-type AlGaN cladding layer in a GaN-based semiconductor laser according to a first embodiment of the present invention. 1 is an energy band diagram of a GaN-based semiconductor laser according to a first embodiment of the present invention. Explained are changes in threshold current and operating voltage when the thickness of the p-type Al _x1 Ga _{1 -x1} N layer constituting the p-type AlGaN cladding layer is changed in the GaN-based semiconductor laser according to the first embodiment of the present invention. It is a figure for doing. The relationship between the measured value of the threshold current of the GaN-based semiconductor laser according to the first embodiment of the present invention, and the measured value and the theoretical value of the Al composition of the p-type AlGaN cladding layer and the threshold current in the conventional GaN-based semiconductor laser. It is a graph to show. It is sectional drawing which shows the detailed structure of the p-type AlGaN clad layer in the GaN-type semiconductor laser by 2nd Embodiment of this invention. It is an energy band figure of the GaN-type semiconductor laser by 2nd Embodiment of this invention. It is a graph which shows the relationship between Al composition of the p-type AlGaN clad layer in a conventional GaN-type semiconductor laser, and operating voltage.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings of the embodiments, the same or corresponding parts are denoted by the same reference numerals.

  FIG. 1 is a sectional view of a GaN-based semiconductor laser according to the first embodiment of the present invention. This GaN-based semiconductor laser is of a ridge stripe type having an AlGaN / GaN / GaInN SCH structure. The active layer has a multiple quantum well (MQW) structure.

  As shown in FIG. 1, in the GaN-based semiconductor laser according to the first embodiment, for example, an undoped GaN layer 3, n is formed on a c-plane sapphire substrate 1 via an undoped GaN buffer layer 2 grown at a low temperature. Type GaN contact layer 4, n-type AlGaN clad layer 5, n-type GaN optical waveguide layer 6, MQW structure active layer 7 using undoped GaInN as a quantum well layer, p-type AlGaN cap layer 8, p-type GaN optical waveguide layer 9. A p-type AlGaN cladding layer 10 and a p-type GaN contact layer 11 having a laminated structure to be described later are sequentially laminated.

The GaN buffer layer 2 has a thickness of, for example, 200 nm. The GaN layer 3 has a thickness of 1 μm, for example. The n-type GaN contact layer 4 has a thickness of 2 μm, for example, and is doped with, for example, silicon (Si) as an n-type impurity. The n-type AlGaN cladding layer 5 is made of, for example, n-type Al _0.06 Ga _0.94 N. The n-type AlGaN cladding layer 5 has a thickness of 1 μm, for example, and is doped with, for example, Si as an n-type impurity. The n-type GaN optical waveguide layer 6 has a thickness of 100 nm, for example, and is doped with, for example, Si as an n-type impurity. The GaInN quantum well layer of the active layer 7 is made of, for example, Ga _0.85 In _0.15 N. In this case, the emission wavelength of the semiconductor laser is about 400 nm. The GaInN quantum well layer of the active layer 7 has a thickness of, for example, 3.5 nm.

The p-type AlGaN cap layer 8 is made of, for example, p-type Al _0.2 Ga _0.8 N. The p-type AlGaN cap layer 8 has a thickness of 10 nm, for example, and is doped with, for example, magnesium (Mg) as a p-type impurity. The p-type GaN optical waveguide layer 9 has a thickness of 100 nm, for example, and is doped with, for example, Mg as a p-type impurity. The p-type AlGaN cladding layer 10 includes two p-type Al _x1 Ga _1-x1 N layers and p-type Al _x2 Ga _1-x2 N layers (where 0 ≦ x2 <x1) having different band gaps and thus different compositions. ≦ 1). The p-type AlGaN cladding layer 10 has a total thickness of 1 μm, for example, and is doped with, for example, Mg as a p-type impurity. A specific configuration of the p-type AlGaN cladding layer 10 will be described in detail later. The p-type GaN contact layer 11 has a thickness of 100 nm, for example, and is doped with, for example, Mg as a p-type impurity.

  The upper layer portion of the p-type AlGaN cladding layer 10 and the p-type GaN contact layer 11 have a predetermined ridge stripe shape extending in one direction. Further, the upper layer portion of the n-type GaN contact layer 4, the n-type AlGaN cladding layer 5, the n-type GaN optical waveguide layer 6, the active layer 7, the p-type AlGaN cap layer 8, the p-type GaN optical waveguide layer 9, and the p-type AlGaN cladding. The lower layer portion of the layer 10 has a predetermined mesa shape. A p-side electrode 12 such as a Ni / Pt / Au electrode or a Ni / Au electrode is provided on the p-type GaN contact layer 11 in the ridge stripe portion. An n-side electrode 13 such as a Ti / Al / Pt / Au electrode is provided on the n-type GaN contact layer 4 adjacent to the mesa portion. This GaN-based semiconductor laser has a resonator length of, for example, 1 mm, and a ridge stripe portion width (stripe width) of, for example, 3.5 μm.

In the GaN-based semiconductor laser according to the first embodiment, the p-type AlGaN cladding layer 10 is composed of a p-type Al _x1 Ga _1-x1 N layer and a p-type Al _x2 Ga _1-x2 N layer having different band gaps. It is characteristic. The p-type AlGaN cladding layer 10 is specifically configured as follows, for example. FIG. 2 shows a detailed structure of the p-type AlGaN cladding layer 10 in the GaN-based semiconductor laser according to the first embodiment. FIG. 3 is an energy band diagram of the GaN-based semiconductor laser according to the first embodiment, and particularly shows its conduction band. In FIG. 3, E _c indicates the lower end of the conduction band.

As shown in FIGS. 2 and 3, in the GaN semiconductor laser according to the first embodiment, the p-type AlGaN cladding layer 10 is a p-type Al _x1 Ga _1-x1 N layer in contact with the p-type GaN optical waveguide layer 9. And a p-type Al _x2 Ga _1-x2 N layer 10b on the p _- type Al _x1 Ga _1-x1 N layer 10a. The p-type Al _x1 Ga _1-x1 N layer 10a has an Al composition larger than that of the p-type Al _x2 Ga _1-x2 N layer 10b, and thus has a high band gap.

Of these p-type Al _x1 Ga _1-x1 N layer 10a and p-type Al _x2 Ga _1-x2 N layer 10b, p-type Al _x1 Ga _1-x1 N layer 10a having a large band gap is an n-type semiconductor layer. It serves as a barrier layer that prevents electrons that have moved from the side from overflowing to the p-type semiconductor layer without being injected into the active layer 7. On the other hand, since the p-type Al _x2 Ga _1-x2 layer 10b occupies most of the p-type AlGaN cladding layer 10 as described later, the influence of the p-type AlGaN cladding layer 10 on the resistance and the optical waveguide in the vertical direction is The p-type Al _x2 Ga _{1 -x2} N layer 10b is dominant. The composition and thickness of the p-type Al _x1 Ga _1-x1 N layer 10a and the p-type Al _x2 Ga _1-x2 N layer 10b constituting the p-type AlGaN cladding layer 10 are such that each layer has a sufficient role. It is selected so that it can be fulfilled.

First, the composition of the p-type Al _x2 Ga _1-x2 N layer 10b is selected so that the resistance value is as low as possible while maintaining the refractive index to such an extent that the optical confinement in the vertical direction is not significantly deteriorated. Specifically, in the case of the Mg-doped p-type Al _x2 Ga _{1 -x2} N layer 10b, the Al composition x2 is preferably 0.05 ≦ x2 ≦ 0.08, for example. After selecting the composition of the p-type Al _x2 Ga _1-x2 N layer 10b in this way, the Al composition x1 of the p-type Al _x1 Ga _1-x1 N layer 10a is used in order to make this layer function as a barrier layer. In other words, the Al composition x2 of the p-type Al _x2 Ga _{1 -x2} N layer 10 b so that a barrier high enough to prevent the overflow of electrons is formed in the conduction band of the p-type AlGaN cladding layer 10. For example, it is desirable to make it larger by 0.02 or more. The composition of the p-type Al _x1 Ga _1-x1 N layer 10a, the band discontinuity of conduction band of the p-type GaN optical guide layer 9 and the p-type Al _x1 Ga _1-x1 N layer 10a is more than 100meV Is selected as follows. An example of the Al composition x1 of the p-type Al _x1 Ga _{1 -x1} N layer 10a and the Al composition x2 of the p-type Al _x2 Ga _{1 -x2} N layer 10b in the first embodiment is x1 = 0.08. , X2 = 0.06.

The thickness t1 of the p-type Al _x1 Ga _1-x1 N layer 10a is required to be at least thick enough to prevent electron tunneling in order to make this layer function as a barrier layer. In order to suppress an increase in operating voltage due to the resistance of the resistor, it is required to be as thin as possible. Specifically, it is desirable to optimize the thickness t1 of the p-type Al _x1 Ga _1-x1 N layer 10a within a range of 20 nm to 100 nm, for example. Here, the present inventor, in a GaN-based semiconductor laser having a structure similar to that shown in FIG. 1, the Al composition x1 and p of the p-type Al _x1 Ga _1-x1 N layer 10 a constituting the p-type AlGaN cladding layer 10. The Al composition x2 of the p _- type Al _x1 Ga _1-x1 N layer 10b is set to x1 = 0.08 and x2 = 0.06, respectively, and the thickness t1 of the p-type Al _x1 Ga _1-x1 N layer 10a is 30 nm, 50 nm, It was examined how the threshold current and the operating voltage change when changing to 80 nm. FIG. 4 summarizes the results of this experiment.

From FIG. 4, the threshold current tends to decrease as the p-type Al _x1 Ga _1-x1 N layer 10a having a thickness of t1 is large, the operating voltage is a p-type Al _x1 Ga _1-x1 N layer 10a thickness t1 It turns out that there is a tendency to decrease, so that it is small. Therefore, when the Al composition x1 of the p _- type Al _x1 Ga _1-x1 N layer 10a and the Al composition x2 of the p-type Al _x1 Ga _1-x1 N layer 10b are x1 = 0.08 and x2 = 0.06, respectively. In order to obtain a predetermined threshold current reduction effect while suppressing an increase in operating voltage, the thickness t1 of the p-type Al _x1 Ga _{1 -x1} N layer 10a is selected to be, for example, 50 nm.

In addition, according to an experiment conducted separately, it has been confirmed that the effect of reducing the threshold current is higher as the Al composition x1 of the p-type Al _x1 Ga _{1 -x1} N layer 10a is larger. Thus, for example, p-type Al _x1 Ga _1-x1 case of the N layer 10a and x1 = 0.11, the required thickness of p-type Al _x1 Ga _1-x1 N layer 10a to obtain comparable effects t1 Is smaller than when x = 0.08.

According to the GaN-based semiconductor laser according to the first embodiment configured as described above, the p-type AlGaN cladding layer 10 has a p-type Al _x1 Ga _1-x1 N layer 10a and a p-type Al _{x2 having} different band gaps. A p-type Al _x1 Ga _1-x1 N layer 10a having a large band gap provided on the side close to the active layer 7 is constituted by the Ga _1-x2 N cladding layer 10b (where 0 ≦ x2 <x1 ≦ 1). By functioning as a barrier layer that prevents the overflow of electrons, the threshold current density is reduced as compared with the prior art. Moreover, the other part of the p-type AlGaN cladding layer 10 is composed of a p _- type Al _x2 Ga _1-x2 N layer 10b having a smaller band gap than the p-type Al _x1 Ga _1-x1 N layer 10a. The increase in resistance of the p-type AlGaN cladding layer 10 as a whole is suppressed.

  Here, the effect of reducing the threshold current density by adopting the configuration of the p-type cladding layer according to the present invention will be described based on experimental results.

FIG. 5 shows the relationship between the Al composition of the p-type AlGaAs cladding layer and the threshold current in a conventional GaN-based semiconductor laser. In FIG. 5, the solid line graph represents the measured value of the threshold current of the conventional GaN-based semiconductor laser. The sample used for this measurement has a laser structure similar to that of the GaN-based semiconductor laser shown in FIG. 1 except that the band gap (composition) of the p-type AlGaN cladding layer is uniform. Was 1 mm, and the stripe width was 3.5 μm. The broken line graph represents the theoretical value of the threshold current when there is no leakage current component. The theoretical value of the threshold current is proportional to the reciprocal of the optical confinement rate Γ. The empty circle (◯) indicates the GaN-based semiconductor laser according to the first embodiment (where the Al composition x1 = 0.08 of the p-type Al _x1 Ga _1-x1 N layer 10a, the thickness t1 = 50 nm, p The measured value of the threshold current of the Al composition x2 = 0.06) of the type Al _x2 Ga _1-x2 N layer 10b is represented.

As shown in FIG. 5, in the conventional GaN-based semiconductor laser in which the band gap of the p-type AlGaN cladding layer is uniform, the Al composition of the p-type AlGaN cladding layer is small. Therefore, the threshold current decreases as the band gap decreases. To rise. Here, a region surrounded by a solid line graph and a broken line graph corresponds to a leakage current component that does not contribute to light emission in the injected current. In contrast, the measured value of the threshold current of the GaN-based semiconductor laser according to the first embodiment is the theoretical value of the threshold current of the conventional GaN-based semiconductor laser in which the Al composition of the p-type AlGaN cladding layer is 0.06. It can be seen that the value is close to. Thus, the threshold current (threshold current density) is reduced in the GaN-based semiconductor laser according to the first embodiment adopting the configuration of the p-type cladding layer according to the present invention as compared with the conventional GaN-based semiconductor laser. This is because the leakage current component is reduced by providing the p-type Al _x1 Ga _{1 -x1} N layer 10a as a barrier layer on the active layer 7 side of the p-type AlGaN cladding layer 10. .

  As described above, according to the GaN semiconductor laser according to the first embodiment, the threshold current density can be reduced with almost no increase in the operating voltage. Further, according to the GaN-based semiconductor laser according to the first embodiment, it is possible to obtain the advantage that the lifetime of the element can be increased and the output can be increased by suppressing the increase of the operating voltage. .

Next explained is the second embodiment of the invention. FIG. 6 shows a detailed structure of the p-type AlGaN cladding layer 10 in the GaN-based semiconductor laser according to the second embodiment of the present invention. FIG. 7 is an energy band diagram of the GaN-based semiconductor laser according to the second embodiment, and particularly shows its conduction band. In FIG. 7, E _c indicates the energy at the lower end of the conduction band.

As shown in FIGS. 6 and 7, in the GaN-based semiconductor laser according to the second embodiment, the p-type AlGaN cladding layer 10 is a p-type Al _x2 Ga _1-x2 N layer in contact with the p-type GaN optical waveguide layer 9. 10b, a p-type Al _x1 Ga _1-x1 N layer 10a thereon, and a p-type Al _x2 Ga _1-x2 N layer 10b thereon. That is, a barrier layer made of p-type Al _x1 Ga _1-x1 N is inserted just in the vicinity of the interface on the active layer 7 side in the p-type AlGaN cladding layer 10 made of p _- type Al _x2 Ga _1-x2 N. It has a structure. In this case, the p-type Al _x1 Ga _1-x1 N layer 10a as the barrier layer is preferably provided at a position of 100 nm or less from the interface of the p-type AlGaN cladding layer 10 on the active layer 7 side. Preferably, the p-type AlGaN cladding layer 10 is provided at a position of 50 nm or less from the interface on the active layer 7 side. That is, the thickness t2 of the p-type Al _x2 Ga _1-x2 N layer 10b between the p _- type GaN optical waveguide layer 9 and the p-type Al _x1 Ga _1-x1 N layer 10a is preferably 100 nn or less, more preferably. Is set to 50 nm or less.

  Since the other configurations of the GaN-based semiconductor laser according to the second embodiment are the same as those of the GaN-based semiconductor laser according to the first embodiment, description thereof will be omitted.

  According to the second embodiment, the same advantages as those of the first embodiment can be obtained.

  Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments, and various modifications based on the technical idea of the present invention are possible.

For example, the numerical values, materials, structures, and the like given in the above-described embodiments are merely examples, and different numerical values, materials, structures, and the like may be used as necessary. Specifically, for example, the p-type AlGaN cladding layer 10 in the first and second embodiments described above is composed of three or more p-type Al _x Ga _1-x N layers (where 0 ≦ x ≦ 1) may be used. More specifically, for example, the p-type AlGaN cladding layer 10 in the first embodiment includes a p-type Al _x1 Ga _1-x1 N layer in contact with the p-type GaN optical waveguide layer 9 and a p-type Al _x2 on the p _- type Al _x1 Ga _1-x1 N layer. It may be composed of a Ga _1-x2 N layer and a p-type Al _x3 Ga _1-x3 N layer (where 0 ≦ x3 <x2 <x1 ≦ 1). When the p-type AlGaN cladding layer 10 is composed of three or more p-type Al _x Ga _1-x N layers having different band gaps as described above, these layers are typically stacked in order of increasing band gap. However, the threshold current density can be reduced with almost no increase in the operating voltage, and the present invention is not limited to this, particularly when the vertical light confinement is not adversely affected. The p-type AlGaN cladding layer 10 in the second embodiment may have different band gaps (compositions) above and below the p-type Al _x1 Ga _1-x1 N layer 10a.

Further, the composition and thickness of each semiconductor layer forming the laser structure mentioned in the first and second embodiments may be different from those exemplified as necessary. In particular, in the first and second embodiments described above, as a typical example, but the p-type cladding layer is constituted by p-type Al _x Ga _1-x N, the p-type cladding layer, B _{x al y Ga z in 1-xyz} N ( However, 0 ≦ x, y, z ≦ 1,0 ≦ x + y + z ≦ 1) may be made from.

  In the first and second embodiments described above, the present invention is applied to a ridge stripe type GaN semiconductor laser. However, the present invention can also be applied to an electrode stripe type GaN semiconductor laser. It is.

  In the first and second embodiments described above, the n-type semiconductor layer is disposed on the substrate side as viewed from the active layer 7 and the p-type semiconductor layer is disposed on the opposite side. A p-type semiconductor layer may be disposed on the substrate side as viewed from the layer 7, and an n-type semiconductor layer may be disposed on the opposite side.

  In the first and second embodiments described above, the present invention has been described for the case where the present invention is applied to a GaN semiconductor laser having a SCH structure, but the present invention is not limited to a GaN semiconductor laser having a DH structure. It can also be applied to a system light emitting diode. The active layer may have a single quantum well (SQW) structure.

1 ... c-plane sapphire substrate, 4 ... n-type GaN contact layer, 5 ... n-type AlGaN cladding layer, 6 ... n-type GaN optical waveguide layer, 7 ... active layer, 9 ... p-type GaN optical waveguide layer, 10 ... p-type AlGaN cladding layer, 10a ... p-type Al _x1 Ga _1-x1 N layer, 10b ... p-type Al _x2 Ga _1-x2 N layer, 11 ... p-type GaN contact layer

Claims (2)

The active layer has a structure sandwiched by an n-type cladding layer and a p-type cladding layer through an optical waveguide layer, and the active layer, the optical waveguide layer, the n-type cladding layer, and the p-type cladding layer are nitride-based. Consisting of III-V compound semiconductors,
The active layer has GaInN as a quantum well layer,
A p-type AlGaN cap layer is provided between the active layer and the optical waveguide layer on the p-type cladding layer side;
The p-type cladding layer includes a p-type Al _x1 Ga _1-x1 N layer having a thickness of 20 nm to 100 nm on the active layer side, and a p-type Al _x2 Ga layer on the p _- type Al _x1 Ga _1-x1 N layer. A semiconductor light emitting device composed of a _1-x2 N layer (where 0.05 ≦ x2 ≦ 0.08 and x1 is 0.02 or more larger than x2). 2. The semiconductor light emitting device according to claim 1, wherein a band discontinuity of a conduction band of the optical waveguide layer on the p-type cladding layer side and the p-type Al _x1 Ga _1-x1 N layer is 100 meV or more.

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