JP4088318B2 - Semiconductor light emitting device, method for manufacturing semiconductor light emitting device, and optical fiber communication system - Google Patents

Description

  The present invention relates to a semiconductor light emitting device, a method for manufacturing the semiconductor light emitting device, and an optical fiber communication system, and more particularly to a semiconductor light emitting device used for a semiconductor laser, a light emitting diode, and the like, a method for manufacturing the semiconductor light emitting device, and an optical fiber communication system.

  Conventionally, InGaAsP / InP materials have been used as semiconductor laser materials in the 1.3 μm band and 1.5 μm band. In addition, in order to spread the optical subscriber system, cost reduction is required, improving the temperature characteristics of the semiconductor laser, controlling the injection current without using an electronic cooling element or the like. Realization of an APC (auto power control) free system for controlling the power to be constant has been studied. However, the InGaAsP / InP-based material cannot make the band discontinuity of the conduction band so large in terms of material, so that the carrier easily overflows, and its temperature dependence is large, so that realization thereof is difficult.

Recently, N-type mixed crystal semiconductor materials containing N in the V group have been studied as new semiconductor materials. For example, in Patent Document 1, a III-V group mixed crystal semiconductor element is formed on a Si substrate. As a means for achieving this, a technique for epitaxially growing an N-based mixed crystal semiconductor, which is a lattice-matched material, is described. This Patent Document 1 proposes a semiconductor laser or a photodiode using a GaN _0.03 P _0.97 cladding layer lattice-matched to a Si substrate and a strained superlattice active layer of GaNP and GaNAs.

  If this technique is used, it becomes possible to epitaxially grow a group III-V mixed crystal semiconductor element on a Si substrate without generating misfit dislocations, and there is a possibility of making it monolithic with an Si electronic element.

  Also, Patent Document 2 describes examples of mixed crystal semiconductors such as InGaNAs, AlGaNAs, and GaNAs that can be lattice-matched with GaAs, InP, and GaP substrates.

  Conventionally, there is no material having a band gap energy smaller than that of GaAs among III-V semiconductors lattice-matched to a GaAs substrate. However, for example, InGaNAs can be lattice-matched to a GaAs substrate, and with a small N composition, a material having a bandgap energy smaller than that of GaAs can be obtained, and light emission of GaAs, which has been difficult to form on a conventional GaAs substrate. It has been found that a light-emitting element having a wavelength longer than the wavelength (such as a 1.3 μm band) can be formed.

  However, although InGaNAs can form a light emitting element having a wavelength longer than that of GaAs, there has been almost no report on its physical properties such as the relationship between the composition and the emission wavelength.

However, the laminated structure is shown in Non-Patent Document 1. According to this, a proposal has been shown in which AlGaAs having a larger band gap energy than the InGaNAs active layer is used as a cladding layer. In Non-Patent Document 1, the InGaNAs active layer and the AlGaAs cladding layer have a structure in direct contact. In this material system, the band discontinuity of the conduction band is large, so that the injected carriers can be efficiently confined in the InGaNAs active layer, and the bad temperature characteristic that is a drawback of the long wavelength laser of the conventional InGaAsP / InP material is remarkably increased. It can be improved, and high output (high power) is also possible.
JP-A-6-334168 JP-A-6-037355 Abstracts of the 1995 International Conference-ce on Solid State Devices and Materials Proceedings (p1016-p1018)

  By the way, in a semiconductor light emitting device formed on a GaAs substrate and having a mixed crystal semiconductor material containing N (nitrogen) in the V group and another V group as an active layer or a well layer, the N source material with a large supply amount is activated. When turning on / off during the growth of the layer or well layer and the barrier layer (supplying or stopping the supply), for example, in the case of vapor phase growth, the gas flow is disturbed, resulting in adverse effects on the interface, There is a problem of affecting the luminous efficiency and the lifetime of the element.

  The present invention relates to a semiconductor light emitting device formed on a GaAs substrate and having a mixed crystal semiconductor material containing N (nitrogen) in the V group and another V group as an active layer or a well layer, as compared with other V group materials. In general, it is not necessary to supply a large amount of N source during the growth of the active layer or well layer and the barrier layer, or to stop the supply. For example, in the case of vapor phase growth, the interface can be easily controlled. It is an object of the present invention to provide a semiconductor light emitting device, a method for manufacturing the semiconductor light emitting device, and an optical fiber communication system capable of increasing the light emission efficiency and extending the device life.

In order to achieve the above object, the invention according to claim 1 is a semiconductor light emitting device in which a semiconductor material made of InGaNAs or InGaNAsP formed on a GaAs substrate is used as an active layer or a well layer.
The active layer or the well layer directly in contact with the semiconductor layer is made of _{Ga d In 1-d N e} As f P 1-e-f (0 ≦ d ≦ 1,0 <e <1,0 ≦ f <1),
The P composition of the semiconductor layer is larger than the P composition of the active layer or the well layer.

  According to a third aspect of the present invention, in the semiconductor light emitting device according to the first or second aspect, the active layer or the well layer among the layers further in direct contact with the semiconductor layer in direct contact with the active layer or the well layer. The semiconductor layer on the opposite side is characterized by being formed of a semiconductor layer not containing Al.

According to a fourth aspect of the present invention, in the semiconductor light-emitting device according to the first or second aspect, the active layer or the well layer among the layers further directly in contact with the semiconductor layer in direct contact with the active layer or the well layer. The semiconductor layer on the opposite side is characterized by comprising a Ga _v In _1-v As _w P _1-w (0 <v ≦ 1, 0 ≦ w ≦ 1) layer.

According to a fourth aspect of the present invention, in the semiconductor light-emitting device according to any one of the first to third aspects, the active layer or well layer, and a barrier layer in direct contact with the active layer or well layer, The active layer or the well layer has a compressive strain with respect to the GaAs substrate, and the barrier layer has a tensile strain with respect to the GaAs substrate.

According to a fifth aspect of the present invention, in the semiconductor light emitting device according to any one of the first to third aspects, the active layer or well layer, and a barrier layer in direct contact with the active layer or well layer, The barrier layer has a compressive strain with respect to the GaAs substrate, and the active layer or the well layer has a tensile strain with respect to the GaAs substrate.

A sixth aspect of the invention is an optical fiber communication system using the semiconductor light emitting device according to any one of the first to fifth aspects.

According to the first to fifth aspects of the present invention, in the semiconductor light emitting device having a semiconductor material made of InGaNAs or InGaNAsP formed on a GaAs substrate as an active layer or a well layer,
The active layer or the well layer directly in contact with the semiconductor layer is made of _{Ga d In 1-d N e} As f P 1-e-f (0 ≦ d ≦ 1,0 <e <1,0 ≦ f <1),
The P composition of the semiconductor layer is larger than the P composition of the active layer or well layer, and by including N in both the active layer or well layer and, for example, the barrier layer, other V group materials In general, it is not necessary to supply an N source having a large supply amount during the growth of the active layer or well layer and the barrier layer, or to stop the supply. For example, in the case of vapor phase growth or the like, Disturbance can be suppressed, whereby the interface can be easily controlled, and a semiconductor light-emitting element with high emission efficiency and long life can be provided.

According to the invention described in claim 6 , since it is an optical fiber communication system using the semiconductor light emitting device according to any one of claims 1 to 5 , a highly reliable optical fiber communication system is provided. be able to.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments described below are preferred embodiments of the present invention, and thus various technically preferable limitations are given. However, the scope of the present invention is particularly limited in the following description. As long as there is no description which limits, it is not restricted to these aspects.

  1 to 3 are diagrams showing a first embodiment of a semiconductor light emitting device and a method for manufacturing the semiconductor light emitting device of the present invention.

  FIG. 1 is a front sectional view of a semiconductor light emitting device 1 to which a first embodiment of a semiconductor light emitting device and a method for manufacturing the semiconductor light emitting device of the present invention is applied.

  In FIG. 1, a semiconductor light emitting device 1 has a clad layer 3, an active layer 4, a clad layer 5 and a cap layer 6 sequentially laminated on a growth substrate 2 formed of an n-type GaAs layer. An InGaNAs layer, which is an N-based mixed crystal semiconductor material, is formed on the GaAs substrate 2.

  The clad layer 3 has a structure (n-type InGaAsP layer) using InGaAsP that is lattice-matched to the growth substrate 2 that is GaAs and has a band gap energy of 1.53 eV, and is a material that does not contain Al.

The active layer 4 that is a light emitting layer is formed on the cladding layer 3 and is an InGaNAs layer, that is, a Ga _a In _1-a N _b As _1-b (0 <b <1) layer that is _a mixed crystal semiconductor containing N. It is formed with.

The clad layer 5 is formed on the active layer 4 and has a structure using InGaAsP (p-type InGaAsP layer). The cap layer 6 is formed of a p ⁺ type GaAs layer.

  Next, a method for manufacturing the semiconductor light emitting element 1 will be described with reference to FIG. FIG. 2 is a schematic configuration diagram of a reaction chamber portion of a MOCVD (Metal Organic Chemical Vapor Deposition) apparatus 10, and the MOCVD apparatus 10 is a horizontal furnace. The MOCVD apparatus 10 is not limited to a horizontal furnace, and may be a vertical furnace.

  The MOCVD apparatus 10 is provided with a cooling tube 13 around a quartz reaction tube 12 having a reaction chamber 11 therein, and the quartz reaction tube 12 is used for supplying a source gas and a carrier gas to the reaction chamber 11. A gas supply port 14 is formed. The quartz reaction tube 12 is connected to an exhaust device 15 for exhausting the gas in the reaction chamber 11 connected to an exhaust device (not shown). A carbon susceptor 16 is disposed in the reaction chamber 11 of the quartz reaction tube 12, and the carbon susceptor 16 is heated by a high-frequency heating coil 17. The temperature of the carbon susceptor 16 heated by the high frequency heating coil 17 is detected by a thermocouple 18. The growth substrate 2 is set on the carbon susceptor 16.

In order to manufacture the semiconductor light emitting device 1 using the MOCVD apparatus 10, a GaAs substrate is set as the growth substrate 2 on the carbon susceptor 16, and the pressure in the reaction chamber 11 is set to 1.3 × 10 10 by an exhaust apparatus (not shown). ^The pressure is reduced to ⁴ Pa. Then, while detecting the temperature with the thermocouple 18, the carbon susceptor 16 is heated with the high frequency heating coil 17, and the GaAs substrate as the growth substrate 2 is controlled to be heated to a predetermined temperature, so that the source gas and the carrier gas are supplied simultaneously. By supplying the reaction chamber 11 through the port 14, the cladding layer 3, the active layer 4, the cladding layer 5 and the cap layer 6 are sequentially stacked on the GaAs substrate which is the growth target substrate 2.

  First, the case where an InGaNAs layer is formed on a GaAs layer that is a growth substrate 2 using the MOCVD apparatus 10 will be described.

As source gas, group III source is TMG (trimethylgallium), TEG (triethylgallium), TMI (trimethylindium), or TEI (triethylindium), As source is AsH ₃ (arsine), N as a raw material, an organic nitrogen compound DMHy (diethylene methylhydrazine), MMHy (monomethyl hydrazine), or using the TBA (tertiary butyl amine) and the like, as the carrier gas, using an _{H 2.}

  When the source gas and the carrier gas are simultaneously supplied into the reaction chamber 11 from the gas supply port 14 under the above conditions, crystals are grown and formed by thermal decomposition of the source gas and the surface reaction of the growth target substrate 2 which is a GaAs layer. .

Then, TMG as a raw material: 4.0 × 10 ⁻⁶ mol / min to 4.0 × 10 ⁻⁵ mol / min, TMI: 4.4 × 10 ⁻⁷ mol / min to 4.4 × 10 ⁻⁶ mol / min, AsH ₃ : 6.0 × 10 ⁻⁵ mol / min (0.4 sccm) to 2.2 × 10 ⁻³ mol / min (46.4 sccm), DMHy: 5.0 × 10 ⁻⁴ mol / H ₂ as a carrier gas is added to min to supply a total of 6 l / min, the partial pressure of AsH ₃ is set to 0.9 to 102 Pa, and the growth temperature is set to 450 ° C. to 700 ° C.

Specifically, for example, TMG: 2.0 × 10 ⁻⁵ mol / min, TMI: 2.2 × 10 ⁻⁶ mol / min, AsH ₃ : 3.3 × 10 ⁻⁴ mol / min (7 sccm), When DMHy: 6.4 × 10 ⁻³ mol / min is used as a raw material gas, the AsH ₃ partial pressure is 15.4 Pa, the growth temperature is 630 ° C., the growth rate is 1.7 μm / h. An In _0.11 Ga _0.89 N _0.04 As _0.96 layer was formed on the growth substrate 2 which is a GaAs layer.

The semiconductor light emitting device 1 formed as a laminated structure using the manufactured In _0.11 Ga _0.89 N _0.04 As _0.96 layer is lattice-matched to the growth substrate 2 made of GaAs, and has an Ar laser. When PL (photoluminescence) measurement was performed at room temperature for the semiconductor light emitting device 1 using (448 nm) as an excitation light source and a Ge-photodiode as a light receiver, the center wavelength was about 1.3 μm. This wavelength band can be applied to the optical communication field.

Moreover, when TMI was decreased and AsH ₃ was increased, an In _0.06 Ga _0.94 N _0.02 As _0.98 layer was formed. This layer was also lattice-matched to the GaAs substrate, and the PL center wavelength was about 1.17 μm. The emission wavelength of such an InGaNAs layer can be increased by increasing the composition of In and N.

That is, in general, when In is added to GaAs, the lattice constant increases and the band gap energy decreases. On the other hand, when N is added to GaAs, the lattice constant is reduced, and the band gap energy is similarly reduced. That is, when N is added to In _x Ga _1-x As, the band gap energy becomes smaller than In _x Ga _1-x As, and there is a condition that the lattice constant matches that of GaAs. Thus, since the InGaNAs layer can be lattice-matched to the GaAs substrate, a light-emitting element having a wavelength longer than the emission wavelength of about 870 nm (room temperature) corresponding to the band gap energy of GaAs is not lattice-matched to conventional GaAs. Compared with the case where InGaAs, which has a larger lattice constant than GaAs, is used for the light emitting layer, it can be formed easily and with high quality, and longer-wavelength devices of 1.3 μm band and 1.5 μm band are formed. It is also possible.

Therefore, by using the MOCVD apparatus 10 and using the In _0.06 Ga _0.94 N _0.02 As _0.98 layer lattice-matched to the growth substrate 2 which is a GaAs layer, FIG. A semiconductor light emitting device 1 having the laminated structure shown was formed. In this case, as described above, the clad layers 3 and 5 are made of an InGaAsP layer that is lattice-matched to the growth substrate 2 that is a GaAs layer and has a band cap energy of 1.35 eV, and does not contain Al. It is formed with.

  A device having an insulating film stripe structure with a stripe width of 5 μm and an element length of 200 μm was fabricated using the wafer of the semiconductor light emitting device 1 and tested for LED (Light Emitting Diode) operation. As a result, an appropriate LED operation was obtained. It was. The emission spectrum at this time is an operating current of 50 mA, a center wavelength of 1176 nm as shown in FIG. 3, and a spectrum reflecting the PL spectrum.

  Thus, in the semiconductor light emitting device 1 of the present embodiment, the cladding layers 3 and 5 in contact with the InGaNAs active layer that is the light emitting layer 4 do not contain Al, that is, the active region (the light emitting layer 4 and the light emitting layer 4). Since the active Al is not contained in the cladding layers 3 and 5) in contact with each other, even in a low growth temperature suitable for a mixed crystal semiconductor containing N, the inside of the manufacturing apparatus that is easily formed on the growth surface of the layer containing Al In addition, the non-radiative recombination center, which is a cause of deterioration that occurs when O (oxygen) in the source cylinder is taken into the surface of the growth target substrate 2 that is a GaAs layer, can be reduced. Therefore, the N-based V group mixed crystal semiconductor light emitting device 1 having high luminous efficiency and long life can be easily manufactured.

  In the above embodiment, the case where the light emitting layer 4 which is an InGaNAs active layer is lattice-matched to the GaAs layer as the growth substrate 2 has been described. However, the InGaNAs active layer 4 is a GaAs layer. It does not have to be perfectly lattice-matched to the growth substrate 2 and may have a thickness within the critical thickness even if it has distortion.

  In the present embodiment, the case where InGaNAs is used as the N-based V group mixed crystal semiconductor has been described. However, the N-based V group mixed crystal semiconductor is not limited to the above-described one. The same applies to other mixed crystal semiconductors such as InGaNAsP.

Further, as the clad layers 3 and 5, a large _{Ga d In 1-d N e} As f P 1-e-f layer band gap energy than the light emitting layer 4 is an active layer (0 ≦ d ≦ 1,0 ≦ e <1, 0 ≦ f ≦ 1) can be used, and in this case, the same effect can be obtained.

Further, in the semiconductor light emitting device 1 having a wavelength of 1.3 μm band (1.25 to 1.35 μm) used for optical communication, the composition of the light emitting layer 4 is made of a material lattice-matched to the growth substrate 2 made of GaAs. It can be obtained by setting it to about In _0.11 Ga _0.89 N _0.04 As _0.96 .

FIG. 4 is a diagram showing a second embodiment of the semiconductor light emitting device and the method for manufacturing the semiconductor light emitting device of the present invention. In this embodiment, In _0.14 Ga ₀ lattice-matched to a GaAs substrate. _.86 N _0.05 As _{0.95 An} active layer (well layer) is used to form a laminated structure.

FIG. 4 is a front cross-sectional view showing a laminated structure of the semiconductor light emitting device 20, and the semiconductor light emitting device 20 is formed on a growth substrate 21 which is an n-type GaAs layer and a clad layer 22 formed of an n-type InGaAsP layer. , A guide layer 23 formed of an InGaAsP layer, a well layer 24 formed of an InGaNAs layer, a guide layer 25 formed of an InGaAsP layer, a cladding layer 26 formed of a p-type InGaAsP layer, and a p ⁺ -type GaAs layer The cap layers 27 are sequentially stacked.

The well layer 24 which is a light emitting layer is formed of an In _0.14 Ga _0.86 N _0.05 As _0.95 layer which is lattice-matched to the growth target substrate 21 which is a GaAs layer.

  The semiconductor light emitting element 20 uses InGaAsP having a lattice match with a growth substrate 21 which is a GaAs layer and having a band gap energy of 1.53 eV for the guide layers (optical waveguide layers) 23 and 25, and the cladding layers 22 and 26. Has a SCH-SQW structure (Separate Confinement Hetero-Structure-Single Quantum Well structure) using InGaAsP having a band gap energy of 1.85 eV lattice-matched to the growth substrate 21 which is a GaAs layer.

  In the semiconductor light emitting device 20 of the present embodiment, as described above, the layers (guide layers 23 and 25) in contact with the well layer (active layer) 24 that is a light emitting layer do not contain Al, that is, in the active region. Since a certain light emitting layer 24 and guide layers 23 and 25 do not contain active Al, a manufacturing apparatus that can be easily formed on the growth surface of a layer containing Al even at a low growth temperature suitable for a mixed crystal semiconductor containing N The non-radiative recombination centers that cause the deterioration that occurs when O (oxygen) in the inside and the raw material cylinder are taken into the substrate surface can be reduced, and the semiconductor light emitting device 20 has high luminous efficiency, It can have a long life.

  When the emission wavelength of the semiconductor light emitting device 20 was measured, the emission wavelength was about 1.3 μm. In this case, by setting the In composition of the well layer 24 to be larger than 11%, the bulk emission wavelength becomes longer than 1.3 μm, but the thickness of the well layer (emission layer) 24 is, for example, 20 nm. The wavelength can be controlled to 1.3 μm by using the quantum effect as follows.

In the present embodiment, the well layer (active layer) 24 which is an InGaNAs layer is an In _0.14 Ga _0.86 N _0.05 As _0.95 layer, but the active layer 24 which is an InGaNAs layer. Other compositions may be used.

  The well layer (active layer) 24 is lattice-matched to the growth substrate 21 which is a GaAs layer. However, the well layer (active layer) 24 does not have to be perfectly lattice-matched, and has a thickness within the critical thickness even if it has strain. If it is.

  Further, in this embodiment, the case where InGaNAs is used as the N-based V group mixed crystal semiconductor is described. However, other mixed crystals such as InGaNAsP containing P are used as the N-based V group mixed crystal semiconductor. Even if it is a semiconductor, it is applicable similarly.

As the guide layers 23 and 25, a Ga _d In having a composition that can be lattice-matched to the substrate 21 to be grown, which is a GaAs layer, or a thickness that is not lattice-matched and has a strain within a critical film thickness even when strained. _{1-d Ne} As _f P _1-ef layer (0 ≦ d ≦ 1, 0 ≦ e <1, 0 ≦ f ≦ 1) can be similarly applied.

  Furthermore, since the semiconductor light emitting element 20 does not contain Al in the cladding layers 22 and 26, the guide layers 23 and 25 may contain N. In this case, the guide layers 23 and 25 need to be made of a material having a smaller band gap energy than the cladding layers 22 and 26.

In this embodiment, the SQW structure is used, but a multiple quantum well structure using a plurality of well layers may be used. In this case, the guide layer having a small band gap energy than that of the cladding layer _{Ga d In 1-d N e} As f P 1-e-f layer (0 ≦ d ≦ 1,0 ≦ e <1,0 ≦ f ≦ 1) can be used.

FIG. 5 is a diagram showing a third embodiment of the semiconductor light emitting device and the method for manufacturing the semiconductor light emitting device of the present invention. In this embodiment, In _0.14 Ga ₀ lattice-matched to a GaAs substrate. _.86 N _0.05 As _0.95 active layer is used to form a laminated structure.

FIG. 5 is a front cross-sectional view showing a laminated structure of the semiconductor light emitting device 30. The semiconductor light emitting device 30 is a clad layer 32 formed of an n-type AlGaAs layer on a growth substrate 31 that is an n-type GaAs layer. , A guide layer 33 formed of an InGaAsP layer, a well layer (light emitting layer) 34 formed of an InGaNAs layer, a guide layer 35 formed of an InGaAsP layer, a cladding layer 36 formed of a p-type AlGaAs layer, and a p ⁺ type A cap layer 37 formed of a GaAs layer is sequentially stacked. The well layer 34 is formed of an In _0.14 Ga _0.86 N _0.05 As _0.95 layer lattice-matched to the growth substrate 31 made of GaAs.

  That is, in the semiconductor light emitting device 30, an InGaAsP layer having a band gap energy of 1.53 eV that is lattice-matched to a growth substrate 31 that is a GaAs layer is used as the guide layers 33 and 35, and an AlGaAs layer having an Al composition of 0.8 is the cladding layer 32. , 36, the SCH-SQW structure.

  In the semiconductor light emitting device 30, the cladding layer 32, 36 formed of the AlGaAs layer is not in direct contact with the well layer 34 formed of the InGaNAs layer as the light emitting layer, that is, the active region (the light emitting layer 34 and the guide layer 33). , 35) does not contain active Al. Therefore, even at a low growth temperature suitable for a mixed crystal semiconductor containing N, a production apparatus and an O ( Non-radiative recombination centers that can cause degradation that occurs when oxygen is incorporated into the substrate surface can be reduced. Therefore, it is possible to form a GaAs substrate lattice-matched long wavelength semiconductor laser with high luminous efficiency and long life.

  When the emission wavelength of the semiconductor light emitting device 30 was measured, the emission wavelength was about 1.3 μm.

  In the present embodiment, the semiconductor light emitting device 30 uses AlGaAs layers for the cladding layers 32 and 36. Here, for example, compared to the case where InGaP is used for the cladding layer, the thermal resistivity of AlGaAs is about ½ times that of InGaP. The thickness of the clad layer is generally required to be about 1.5 μm, and a material with a low thermal resistivity has a smaller temperature rise in the active region during current injection, thus suppressing problems such as a decrease in efficiency. This is preferable. From this point of view, AlGaAs is used for the cladding layers 32 and 36 in the element of the present embodiment.

  Since the AlGaAs layer having a low thermal resistivity, a low refractive index and a large band gap energy is used for the cladding layers 32 and 36 outside the guide layers 33 and 35 which are thin InGaAsP, the carrier and light The confinement efficiency was further improved, the threshold current density was lowered, and the luminous efficiency was increased. Thus, the semiconductor light emitting device 30 which is a GaAs substrate lattice-matched long wavelength semiconductor laser having a long device lifetime, a low threshold current density and a high luminous efficiency could be formed.

  The well layer (active layer) 34 that is an InGaNAs layer may have another composition, and may not be completely lattice-matched to the growth target substrate 31 that is a GaAs layer. Any thickness within the range is acceptable. In this embodiment, the case of InGaNAs as the N-based group V mixed crystal semiconductor has been described. However, the present invention can also be applied to other mixed crystal semiconductors such as InGaNAsP containing P.

Further, the guide layers 33 and 35, the lattice matching possible compositions to be growth substrate 31 is a GaAs layer or an even be not lattice matched have a strain within the critical film thickness of the thick In _x Ga _1-x As _y P _1-y (0 ≦ x <1, 0 ≦ y ≦ 1) may be used. Further, the Al composition of the clad layers 32 and 35 which are AlGaAs layers may be other compositions as long as the conduction band energy is larger than that of the guide layers 33 and 35.

  FIG. 6 is a diagram showing a semiconductor light emitting device and a method for manufacturing the semiconductor light emitting device according to a fourth embodiment of the present invention. In this embodiment, lattice matching is applied to a growth substrate which is a GaAs layer as a cladding layer. The InGaAlP layer is used.

In FIG. 6, a semiconductor light emitting device 40 is formed on a growth substrate 41 made of n-type GaAs, with a cladding layer 42 made of an n-type InGaAlP layer, a guide layer 43 made of an InGaAsP layer, and an InGaNAs layer. A well layer 44, a guide layer 45 formed of an InGaAsP layer, a cladding layer 46 formed of a p-type InGaAlP layer, and a p ⁺ -type GaAs (cap layer) 47 are sequentially stacked.

  In the semiconductor light emitting device 40, clad layers 42 and 46 are formed of an InGaAlP layer lattice-matched to a growth substrate 41 formed of a GaAs layer. The InGaAlP system has a composition with a larger band gap energy than the AlGaAs system, and can increase the carrier and optical confinement efficiency. Further, although the AlGaAs system has a slight shift in lattice constant from the growth substrate 41 which is a GaAs layer, the InGaAlP system has the advantage that it can be completely lattice matched.

  Therefore, it is possible to form the semiconductor light emitting device 40 which is a GaAs substrate lattice matching long wavelength semiconductor laser having high luminous efficiency and long life.

  FIG. 7 is a diagram showing a fifth embodiment of the semiconductor light emitting device and the method for manufacturing the semiconductor light emitting device of the present invention. In this embodiment, the InGaNAs active layer is not perfectly lattice matched to the GaAs substrate. The thickness is within the critical film thickness and has strain.

In FIG. 7, a semiconductor light emitting device 50 is formed on a growth substrate 51 made of n-type GaAs, with a clad layer 52 made of an n-type AlGaAs layer, a guide layer 53 made of an InGaAsP layer, and an InGaNAs layer. A well layer (compressed layer) 54, a guide layer 55 formed of an InGaAsP layer, a cladding layer 56 formed of a p-type AlGaAs layer, and a cap layer 57 formed of p ⁺ -type GaAs are sequentially stacked.

  In the semiconductor light emitting device 50, the well layer 54 formed of the InGaNAs layer has a larger In composition than the well layer 34 formed of the InGaNAs layer of the semiconductor light emitting device 30 of the third embodiment. The constant is larger than that of the growth target substrate 51 that is a GaAs layer, and has a compressive strain. Further, when the emission wavelength of the semiconductor light emitting device 50 was measured, the emission wavelength was about 1.3 μm. In order to use the quantum effect with a lattice-matching material as in the third embodiment, by setting the In composition to be larger than 11% and the N composition to be larger than 4% when the wavelength is 1.3 μm, Is possible.

  However, N easily leaves the growing substrate surface, and it is difficult to obtain an N-based V group mixed crystal semiconductor having a large N composition. Further, according to the experiment by the inventors of the present application, when the N composition is increased, the PL (photoluminescence) intensity is weakened, and deterioration of crystallinity is confirmed. Therefore, the current situation is that the longer the wavelength, the harder it is to produce.

However, in InGaNAs having the same N composition, the larger the In composition, the larger the lattice constant, and the longer the emission wavelength. Therefore, using this property, for example, in order to lattice-match the grown substrate 51 formed of a GaAs layer with a wavelength of 1.3 μm, In _0.11 Ga _0.89 N _0.04 As _0.96 Although it is necessary, if the In composition is larger than 11%, the wavelength of 1.3 μm can be obtained under the condition that the N composition is smaller than 4%. In this case, the lattice constant is larger than that of the growth substrate 51 that is a GaAs layer. Thus, when the lattice constant is made larger than that of the growth target substrate 51 that is a GaAs layer, the target wavelength can be obtained with an N composition smaller than that of the lattice matching condition. Luminous efficiency can be increased.

  Therefore, in the semiconductor light emitting device 50 of the present embodiment, the In composition is made larger than 11%, and the lattice constant of the well layer (active layer) 54 that is an InGaNAs layer is made larger than that of the growth target substrate 51 that is a GaAs layer. Therefore, it can be formed with a small N composition, the semiconductor light emitting device 50 can be easily manufactured, and the luminous efficiency can be increased. In addition, the semiconductor light emitting device 50 of the present embodiment also has an effect of reducing the threshold current density due to the strained quantum well effect. Therefore, it is effective as a light source for optical fiber communication. Of course, the InGaNAs layer can be set to other wavelengths.

  FIG. 8 is a diagram showing a semiconductor light emitting device to which the sixth embodiment of the semiconductor light emitting device and the method for manufacturing the semiconductor light emitting device of the present invention is applied. In this embodiment, the InGaNAs active layer is completely formed on the GaAs substrate. Is strained at a thickness within the critical thickness without lattice matching.

FIG. 8 is a front sectional view of the semiconductor light emitting device 60 of the present embodiment. In FIG. 8, the semiconductor light emitting device 60 is formed of a growth substrate 61 formed of an n-type GaAs layer and an n-type AlGaAs layer. Cladding layer 62, guide layer 63 formed of InGaAsP layer, strain compensation type MQW (multiple quantum well) structure layer 64, guide layer 65 formed of InGaAsP, cladding layer 66 formed of p-type AlGaAs layer and p A cap layer 67 formed of a ⁺ type GaAs layer is sequentially laminated.

  The semiconductor light emitting device 60 differs from the fifth embodiment in the following points. That is, the active region of the semiconductor light emitting device 60 is formed of a strain compensation type MQW (multiple quantum well) structure layer 64, and the growth constant of the InGaNAs well layer of the MQW structure layer 64 is formed of GaAs. It has a compressive strain larger than that of the substrate 61, and the lattice constant of the InGaAsP barrier layer of the MQW structure layer 64 has a smaller tensile strain than that of the growth substrate 61 formed of GaAs.

  The InGaNAsP well layer and the InGaAsP barrier layer of the MQW structure layer 64 are both changed in composition so that the lattice constant is made larger or smaller than that of the GaAs growth substrate 61 under the same band gap energy. It is a material system that can be changed. This is not possible with an AlGaAs-based barrier layer. That is, compared to the case of using an AlGaAs-based barrier layer, by using an InGaAsP-based barrier layer, it becomes possible to compensate for the strain of the InGaNAsP-based well layer, and by controlling to a composition having an appropriate strain amount, The degree of freedom of composition of the well layers can be increased, and the number of well layers can be increased.

  In the present embodiment, the InGaNAs well layer of the MQW structure 64 is a compression layer, and the InGaAsP barrier layer is a tensile strain layer. However, the InGaNAs well layer may be a tensile strain layer and the InGaAsP barrier layer may be a compression strain layer. By controlling to a composition having an appropriate amount of strain, the effect of a strained quantum well can be obtained.

  FIG. 9 is a diagram showing a seventh embodiment of the semiconductor light-emitting device and the method for manufacturing the semiconductor light-emitting device according to the present invention. In this embodiment, a strain using a GaInNAs layer as a well layer and GaInNAsP as a barrier layer is shown. This is applied to one using a compensation type MQW (multiple quantum well) structure.

FIG. 9 is a front sectional view of the semiconductor light emitting device 70 of the present embodiment. In FIG. 9, the semiconductor light emitting device 70 is formed of a growth substrate 71 formed of an n-type GaAs layer and an n-type AlGaAs layer. Cladding layer 72, guide layer 73 formed of InGaAsP layer, strain compensation type MQW (multiple quantum well) structure layer 74, guide layer 75 formed of InGaAsP, cladding layer 76 formed of p-type AlGaAs layer, and p A cap layer 77 formed of a ⁺ -type GaAs layer is sequentially stacked.

  The semiconductor light emitting device 70 has a lattice constant of the InGaNAs well layer of the strain compensation type MQW (multiple quantum well) structure layer 74 that is larger than that of the growth substrate 71 which is a GaAs layer. The lattice constant of the InGaNAsP barrier layer of the structural layer 74 has a tensile strain smaller than that of the growth substrate 71 that is a GaAs layer. Further, the semiconductor light emitting device 70 uses AlGaAs layers for the cladding layers 72 and 76, and has a structure in which a layer containing Al and a layer containing N are not in direct contact with each other.

  Therefore, also in the semiconductor light emitting device 70 of the present embodiment, an effect using a strain compensation type MQW (multiple quantum well) structure can be obtained.

In the present embodiment, the growth conditions of the InGaNAsP barrier layer are obtained by adding a P raw material (PH ₃ in this embodiment) to the growth conditions of the InGaNAs well layer of the MQW structure layer 74. The supply amount of the raw materials of Ga, N, and As is not changed.

  In general, when P is added to InGaNAs, the band gap energy increases and the lattice constant decreases. When the lattice constant of the InGaNAs well layer of the MQW structure layer 74 of the semiconductor light emitting device 70 of the present embodiment is larger than the growth substrate 71 which is a GaAs layer, the lattice constant is changed to GaAs by controlling the addition amount of P. It can be lattice-matched to the growth substrate 71 which is a layer, or can be made smaller than the growth substrate 71 which is a GaAs layer.

  In addition, since the MQW structure layer 74 of the semiconductor light emitting device 70 according to the present embodiment contains N in both the well layer and the barrier layer, the raw material of N generally supplied in a larger amount than other V group raw materials is used. Since it is not necessary to turn on / off (do not supply to the growth substrate 71) during the growth of the well layer and the barrier layer, the interface can be easily controlled.

  Note that in this embodiment mode, the supply amount of the In, Ga, N, and As raw materials is not changed, but the present invention can be similarly applied even if the supply amount is changed.

  Further, in the present embodiment, the case where P is not included in the well layer of the MQW structure layer 74 has been described. However, even if P is included in the well layer, the P composition of the barrier layer is further increased. It can be applied by increasing the band gap energy of the barrier layer.

  FIG. 10 is a diagram showing an eighth embodiment of the semiconductor light emitting device and the method for manufacturing the semiconductor light emitting device of the present invention. This embodiment is a high output for exciting a solid laser in the 0.8 μm band or the like. This is applied to a semiconductor laser.

FIG. 10 is a front sectional view of the semiconductor light emitting device 80 of the present embodiment. In FIG. 10, the semiconductor light emitting device 80 is formed of a growth substrate 81 formed of an n-type GaAs layer and an n-type InGaP layer. Cladding layer 82, guide layer 83 formed of InGaAsP layer, well layer (active layer) 84 formed of InGaNAsP layer, guide layer 85 formed of InGaAsP layer, cladding layer 86 formed of p-type InGaP layer And a cap layer 87 formed of a p ⁺ -type GaAs layer is sequentially stacked.

  That is, the semiconductor light emitting device 80 has an InGaNAsP layer having a band gap energy of 1.54 eV as an active layer (well layer) 84 and a GaAs layer as guide layers (optical waveguide layers) 83 and 85. An InGaAsP layer lattice matched to the substrate 81 and having a band gap energy of 1.83 eV, and InGaP having a band gap energy of 1.91 eV lattice matched to the substrate 81 to be grown as a GaAs layer as the cladding layers 82 and 86. SCH-SQW structure using The oscillation wavelength of the semiconductor light emitting device 80 is about 0.81 μm.

  Conventionally, in a high-power semiconductor laser for exciting a solid laser in the 0.8 μm band or the like, AlGaAs is often used for a cladding layer and a guide layer in contact with an active layer. However, optical damage is likely to occur, and reliability is high. There was a problem. Thus, Al-free material systems have been prototyped using InGaAsP-based materials, but InGaAsP-based materials have a smaller band offset of the conduction band than AlGaAs-based materials, leading to greater carrier leakage from the active layer. Although the reliability is good, other device characteristics are not sufficient as a high-power semiconductor laser.

  In contrast to such a conventional high-power semiconductor laser, the semiconductor light emitting device 80 of the present embodiment has an active layer (well layer) 84 formed of InGaNAsP and added with N. Thus, when N is added, the band gap can be reduced and the energy of the conduction band and the valence band can be reduced. Therefore, even when an InGaAs-based material is used for the cladding layers 82 and 86 and the guide layers 83 and 85, the band offset of the conduction band is increased and the carrier leak from the active layer 84 is reduced. As a result, the threshold current density is lowered, and high temperature characteristics and the like can be improved.

  In the semiconductor light emitting device 80, the layer in contact with the InGaNAsP layer that is the light emitting layer 84 does not contain Al, that is, the active region (the light emitting layer 84 and the guide layers 83 and 85) does not contain active Al. Therefore, even at a low growth temperature suitable for a mixed crystal semiconductor containing N, O (oxygen) in a manufacturing apparatus and a raw material cylinder that are easily formed on the growth surface of an Al-containing layer is taken into the substrate surface and generated. Non-radiative recombination centers that cause the deterioration to occur can be reduced. Therefore, it is possible to easily manufacture a high-power semiconductor light emitting device 80 that is a high-power semiconductor laser with high reliability and good other device characteristics.

  In the present embodiment, an InGaNAsP layer is used as the active layer 84, but other compositions may be used.

  Further, although the case where the active layer 84 that is an InGaNAsP layer is completely lattice-bonded to the GaAs layer as the growth substrate 81 has been described, it is not completely lattice-matched to the growth substrate 81 that is a GaAs layer. The thickness may be within the critical thickness even if it has distortion.

Further, as the guide layers 83 and 85, a composition that can be lattice-matched to the growth target substrate 81 that is a GaAs layer, or a thickness that is within the critical film thickness even if there is distortion without lattice matching, that is, even _{Ga d in 1-d N e} as f P 1-e-f layer (0 ≦ d ≦ 1,0 ≦ e <1,0 ≦ f ≦ 1), can be applied similarly.

  In the semiconductor light emitting device 80, since the clad layers 82 and 86 do not contain Al, the guide layers 83 and 85 may contain N. In this case, the guide layers 83 and 85 need to be made of a material having a smaller band gap energy than the cladding layers 82 and 86.

Furthermore, although the SQW structure is used in this embodiment, a multiple quantum well structure using a plurality of well layers may be used. In this case, the barrier layer has a Ga _d In _{1-d Ne} As _f P _1-ef layer (0 ≦ d ≦ 1, 0 ≦ e <1, 0 ≦ f ≦) having a smaller band gap energy than the cladding layer. 1) can be used.

The invention made by the present inventor has been specifically described based on the preferred embodiments. However, the present invention is not limited to the above, and various modifications can be made without departing from the scope of the invention. Needless to say.

1 is a front cross-sectional view of a growth layer of a semiconductor light emitting device to which a first embodiment of a semiconductor light emitting device and a method for manufacturing the semiconductor light emitting device of the present invention is applied. The schematic block diagram of the reaction chamber part of the MOCVD apparatus for manufacturing the semiconductor light-emitting device of FIG. The figure which shows the emission spectrum of the semiconductor light-emitting device of FIG. The front sectional view of the growth layer of the semiconductor light emitting element to which the second embodiment of the semiconductor light emitting element and the method for manufacturing the semiconductor light emitting element of the present invention is applied. The front sectional view of the growth layer of the semiconductor light emitting element to which the third embodiment of the semiconductor light emitting element and the method for manufacturing the semiconductor light emitting element of the present invention is applied. The front sectional view of the growth layer of the semiconductor light emitting element to which the fourth embodiment of the semiconductor light emitting element and the method for manufacturing the semiconductor light emitting element of the present invention is applied. The front sectional view of the growth layer of the semiconductor light emitting element to which the fifth embodiment of the semiconductor light emitting element and the method for manufacturing the semiconductor light emitting element of the present invention is applied. The front sectional view of the growth layer of the semiconductor light emitting element to which the sixth embodiment of the semiconductor light emitting element and the method for manufacturing the semiconductor light emitting element of the present invention is applied. The front sectional view of the growth layer of the semiconductor light emitting element to which the seventh embodiment of the semiconductor light emitting element and the method for manufacturing the semiconductor light emitting element of the present invention is applied. The front sectional view of the growth layer of the semiconductor light emitting element to which the eighth embodiment of the semiconductor light emitting element and the method for manufacturing the semiconductor light emitting element of the present invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor light emitting element 2 Growing substrate 3 Cladding layer 4 Active layer 5 Cladding layer 6 Cap layer 10 MOCVD apparatus 11 Reaction chamber 12 Quartz reaction tube 13 Cooling tube 14 Gas supply port 15 Exhaust tube 16 Carbon susceptor 17 High frequency heating coil 18 Thermocouple 20, 30, 40, 50, 60, 70, 80 Semiconductor light emitting device 21, 31, 41, 51, 61, 71, 81 Growth substrate 22, 32, 42, 52, 62, 72, 80 Clad layer 23, 33 , 43, 53, 63, 73, 83 Guide layer 24, 34, 44, 54, 84 Well layer 25, 35, 45, 55, 65, 75, 85 Guide layer 26, 36, 46, 56, 66, 76, 86 Clad layer 27, 37, 47, 57, 67, 77, 87 Cap layer 64, 74 Strain compensated MQW structure layer

Claims (6)

In a semiconductor light emitting device having a semiconductor material made of InGaNAs or InGaNAsP formed on a GaAs substrate as an active layer or a well layer,
The active layer or the well layer directly in contact with the semiconductor layer is made of _{Ga d In 1-d N e} As f P 1-e-f (0 ≦ d ≦ 1,0 <e <1,0 ≦ f <1),
A semiconductor light emitting device, wherein the P composition of the semiconductor layer is larger than the P composition of the active layer or the well layer. 2. The semiconductor light emitting device according to claim 1, wherein the semiconductor layer on the side opposite to the active layer or the well layer among the layers further directly in contact with the semiconductor layer directly in contact with the active layer or the well layer is a semiconductor layer not containing Al. A semiconductor light-emitting element formed. 2. The semiconductor light emitting device according to claim 1, wherein the semiconductor layer on the side opposite to the active layer or the well layer among the layers further directly in contact with the semiconductor layer directly in contact with the active layer or the well layer is Ga _v In _1-v As. A semiconductor light emitting device comprising a _w P _1-w (0 <v ≦ 1, 0 ≦ w ≦ 1) layer. 4. The semiconductor light emitting device according to claim 1, comprising the active layer or well layer and a barrier layer in direct contact with the active layer or well layer, wherein the active layer or well layer is A semiconductor light emitting device having a compressive strain with respect to a GaAs substrate and the barrier layer having a tensile strain with respect to the GaAs substrate. 4. The semiconductor light emitting device according to claim 1, comprising: the active layer or well layer; and a barrier layer in direct contact with the active layer or well layer, wherein the barrier layer is formed on a GaAs substrate. A semiconductor light emitting device having compressive strain, wherein the active layer or well layer has tensile strain with respect to a GaAs substrate. An optical fiber communication system using the semiconductor light emitting device according to any one of claims 1 to 5.

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