JP2008098682A - Semiconductor light emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-performance and long wavelength semiconductor light emitting element in which the impairment of crystallinity is prevented. <P>SOLUTION: In a semiconductor light emitting element having an active layer 3 including a strained quantum well layer 2, and a clad layer 4 for confining light and a carrier formed on a semiconductor substrate 1 and having an oscillation wavelength in a 1.3 μm band, the strained quantum well layer 2 contains In and N, an N composition occupies 0-1% of a group V element, an In composition occupies 30% or more of a group III element, and the amount of the strain of the strained quantum well layer 2 for the semiconductor substrate 1 and the clad layer 4 exceeds 2%. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a semiconductor light emitting device.

  Conventionally, an optical communication system using an optical fiber is mainly used in a trunk system, but in the future, it is considered to be used in a subscriber system including each home. In order to realize this, it is necessary to reduce the size and cost of the system, and it is necessary to realize a system that does not require a Peltier element for temperature control of a semiconductor light emitting element used for optical communication.

  In order to realize such an optical communication system, a semiconductor light emitting device used for optical communication is desired to have a high characteristic temperature element with low threshold operation and little characteristic change due to temperature change. In general, when a material having a lattice constant different from that of a semiconductor substrate is formed on a semiconductor substrate, a thickness up to a critical film thickness estimated from a strain associated with the difference in lattice constant can be formed. However, in the conventional GaInPAs / InP-based materials, there is no material that can increase the band discontinuity of the conduction band, and it has been difficult to achieve a high characteristic temperature.

  In order to improve this, for example, Patent Document 1 proposes a semiconductor light emitting element in which an active layer is formed on a ternary substrate made of GaInAs. In this semiconductor light emitting device, since GaInAs is used for the substrate, a wide gap material can be formed on the GaInAs substrate, so that it is possible to obtain band discontinuity of a large conduction band that could not be realized on the InP substrate. .

  Attempts have also been made to form long wavelength lasers on GaAs substrates. Patent Document 2 proposes a semiconductor laser device in which a GaInAs lattice relaxation buffer layer having a lattice constant larger than that of GaAs is formed on a GaAs substrate, and an active layer is formed thereon. In this semiconductor laser device, since a material having a lattice constant larger than that of GaAs can be formed on the GaInAs lattice relaxation buffer layer, as in the semiconductor light emitting device proposed in Patent Document 1, the band discontinuity of a large conduction band is achieved. Can be obtained.

  Further, a material having a wider gap than that formed on the InP substrate or the GaInAs ternary substrate can be formed on the GaAs substrate. However, conventionally, there has been no band gap active layer material corresponding to a long wavelength such as a 1.3 μm band. That is, when GaInAs is formed on a GaAs substrate, GaInAs increases in wavelength with an increase in In composition, but with an increase in strain. Since the limit strain is about 2%, it is said that the wavelength of 1.1 μm is the limit (Non-Patent Document 1).

  Therefore, as another method, Patent Document 3 proposes forming a GaInNAs-based material on a GaAs substrate. GaInNAs is a group III-V mixed crystal semiconductor containing N and other group V elements. When a GaInNAs material is formed on a GaAs substrate, it is possible to lattice-match the lattice constant to GaAs by adding N to GaInAs, which has a larger lattice constant than GaAs. The band gap energy is reduced due to the fact that the band gap energy is small compared to the above, and light emission in the 1.3 μm and 1.5 μm bands becomes possible. In Non-Patent Document 2, a band lineup is calculated by Kondo et al. When a GaInNAs material is formed on a GaAs substrate, a GaAs lattice matching system is used as described above, so that wide gap AlGaAs can be used for the cladding layer. In addition, the addition of N reduces the band gap and decreases the energy levels of the conduction band and valence band, thereby increasing the band discontinuity of the conduction band at the heterojunction. For this reason, it is expected that a high characteristic temperature semiconductor light emitting device can be realized.

Regarding the structure of the GaInNAs laser, the edge emitting type is proposed in Patent Document 4 and Patent Document 5, and the surface emitting type is proposed in Patent Document 6 and Patent Document 7. In recent years, a 1.3 μm-GaInNAs laser on a GaAs substrate has been actually realized. In other words, a double heterostructure (non-patent document 3) using a thick film GaInNAs having a nitrogen composition of 3% and an In composition of 10% that is lattice-matched on the GaAs substrate (non-patent document 3), or a GaInNAs having a nitrogen composition of 1% and an In composition of 30%. The compression strain single quantum well structure (nonpatent literature 4) used is proposed.
JP-A-6-275914 JP-A-7-193327 JP-A-6-37355 JP-A-8-195522 JP-A-10-126044 Japanese Patent Laid-Open No. 9-237942 Japanese Patent Laid-Open No. 10-74979 IEEE Photonics. Technol. Lett. Vol.9 (1997) pp.1319-1321 Jpn.J.Appl.Phys.Vol.35 (1996) pp.1273-1275 Elecron. Lett. Vol.33 (1997) pp.1386-1387 IEEE Photonics. Technol. Lett. Vol.10 (1998) pp.487-488

  However, the ternary substrate made of GaInAs proposed in Patent Document 1 is difficult to produce. Further, the structure in which the GaInAs lattice relaxation buffer layer proposed in Patent Document 2 is basically a lattice mismatch system with respect to the substrate has a problem in terms of lifetime. In addition, a group III-V mixed crystal semiconductor containing nitrogen and other group V elements such as GaInNAs has a problem that the crystallinity is greatly deteriorated as the nitrogen composition is increased.

  An object of the present invention is to provide a high-performance long-wavelength semiconductor light-emitting element in which deterioration of crystallinity is prevented.

  In order to achieve the above object, according to the first aspect of the present invention, an active layer including a strained quantum well layer and a cladding layer for confining light and carriers are formed on a semiconductor substrate, and an oscillation wavelength is in a 1.3 μm band. In the semiconductor light emitting device, the strained quantum well layer contains In and N, the N composition in the group V element is 0 to 1%, and the In composition in the group III element is in a range larger than 30%. The strain amount of the strained quantum well layer with respect to the substrate and the cladding layer is characterized by a strain amount exceeding 2%.

  According to a second aspect of the present invention, an active layer including a strained quantum well layer and a clad layer for confining light and carriers are formed on a semiconductor substrate, and a semiconductor light emitting device having an oscillation wavelength of 1.3 μm band, The strain quantity of the strain quantum well layer with respect to the semiconductor substrate and the clad layer is greater than 2%, and the plane orientation of the semiconductor substrate is within a range of 5 ° from (100). It is characterized by that.

  According to a third aspect of the present invention, in the semiconductor light emitting device according to the first or second aspect, GaInP or GaInPAs is used as the cladding layer.

  According to a fourth aspect of the present invention, in the semiconductor light-emitting device according to the first or second aspect, the semiconductor light-emitting device is a surface-emitting type.

  According to a fifth aspect of the present invention, in the semiconductor light emitting device according to the first or second aspect, a barrier layer for compensating stress is formed in the active layer in the vicinity of the strained quantum well layer. It is characterized by that.

  According to the first to fifth aspects of the present invention, in the semiconductor light emitting device having the oscillation wavelength of 1.3 μm band, the strain amount of the strain quantum well layer with respect to the semiconductor substrate and the cladding layer is greater than 2%. Therefore, the crystallinity can be improved.

  In particular, according to the invention described in claim 3, in the semiconductor light emitting device according to claim 1 or 2, GaInP or GaInPAs is used as the cladding layer, and GaInP or GaInPAs containing no Al is more than AlGaAs. Since a good crystal can be obtained at a low growth temperature, it is preferable to produce a high strain quantum well laser that is preferably grown at a low temperature because it is not easily affected by heat such as diffusion, and a high strain quantum well with good crystallinity. It is easy to obtain a well layer. In addition, when GaInP (As) is used as the lower cladding layer between the semiconductor substrate and the quantum well active layer having a large strain, a quantum well layer having a good large strain that is not easily affected by defects generated in the cladding layer is grown. it can. Further, since the element characteristics are not easily affected by defects generated in the clad layer, the light emitting efficiency is higher than that in the case of using an AlGaAs material, and an element having a long life can be obtained. In the case of a laser, the threshold current density is low.

According to a fourth aspect of the present invention, in the semiconductor light emitting device according to the first or second aspect, the semiconductor light emitting device is a surface light emitting type. That is, when a semiconductor light emitting device of a long wavelength band can be formed on a GaAs substrate, an Al (Ga) As / GaAs multilayer mirror having a large refractive index difference can be used, so that a thin thickness is sufficient, and AlAs is oxidized. Al _x O _y can be used to narrow the current, and is extremely effective as compared with a conventional long-wavelength surface emitting semiconductor light emitting device on an InP substrate.

According to a fifth aspect of the present invention, in the semiconductor light emitting device according to the first or second aspect, a barrier layer for compensating stress is formed in the active layer in the vicinity of the strained quantum well layer. If there is a barrier layer (strain compensation layer) that alleviates strain in the well layer, the quality of the well layer can be improved and the number of well layers can be increased. It is effective because the structure can be optimized for high performance. In particular, in the invention described in claim 5, when the well layer has a high compressive strain, it is possible to widen the range of conditions for manufacturing by compensating the stress.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a configuration example of a semiconductor light emitting device according to the present invention. In the semiconductor light emitting device (semiconductor laser) shown in FIG. 1, an active layer 3 including a strained quantum well layer (light emitting layer) 2 and a clad layer 4 for confining light and carriers are formed on a semiconductor substrate 1. The strain amount of the strained quantum well layer 2 with respect to the substrate 1 and the clad layer 4 is greater than 2%.

  Here, GaAs is used for the semiconductor substrate 1. Further, GaInP or GaInPAs is used as the cladding layer 4. Further, the semiconductor light emitting device (semiconductor laser) of FIG. 1 is a surface emitting type.

Further, in the semiconductor light emitting device (semiconductor laser) of FIG. 1, the strained quantum well layer 2 is formed of Ga _x In _{1 -x Ny} As _{1 -y} (0 ≦ x ≦ 1, 0 ≦ y <1). Yes. Then, regarding Ga _x In _1-x N _y As _1-y (0 ≦ x ≦ 1, 0 ≦ y <1) which is the strained quantum well layer 2, the composition wavelength of GaInAs when nitrogen is not included However, the wavelength is longer than 1.12 μm. More specifically, the composition of In in the group III element of the strained quantum well layer 2 is greater than 30%. Further, the nitrogen composition in the group V element of the strained quantum well layer 2 is in the range of 0 to 1%.

  Further, in the semiconductor light emitting device (semiconductor laser) of FIG. 1, the plane orientation of the semiconductor substrate 1 is within a range of an inclination angle of 5 ° from (100).

  In the semiconductor light emitting device (semiconductor laser) shown in FIG. 1, a barrier layer for compensating stress is formed in the active layer 3 in the vicinity of the strained quantum well layer 2. FIG. 2 is a diagram showing an example of an active layer in which a barrier layer is formed. In the example of FIG. 2, the active layer 3 includes well layers 2a and 2b, well layers 2a and 2b, and well layers 2a. GaNPAs barrier layers 5a, 5b, and 5c provided below and well layer 2b are formed.

  In the present invention, in a semiconductor light emitting device (semiconductor laser) in which an active layer 3 including a strained quantum well layer 2 and a clad layer 4 for confining light and carriers are formed on a semiconductor substrate 1, the semiconductor substrate 1 and the clad The strain amount of the strain quantum well layer 2 with respect to the layer 4 is greater than 2%, and a semiconductor light emitting device (semiconductor laser) having a wavelength that cannot be obtained conventionally is obtained by crystal growth of a material composition that cannot be obtained conventionally. Can do.

  Further, since the semiconductor substrate 1 is a GaAs substrate, a wide gap material such as AlGaAs, AlAs, GaInP, and AlInP that cannot be grown thickly on the InP substrate can be grown as a cladding layer of the semiconductor light emitting device, and a long wavelength band can be obtained. It is extremely excellent as a substrate for semiconductor light emitting devices (semiconductor lasers).

Further, in the semiconductor light emitting device (semiconductor laser) of FIG. 1, the strained quantum well layer 2 is formed of Ga _x In _{1 -x} N _y As _{1 -y} (0 ≦ x ≦ 1, 0 ≦ y <1). Therefore, it is possible to form a light emitting layer of a semiconductor light emitting device (semiconductor laser) having a wavelength up to about 1.2 μm with GaInAs with y = 0, and with a wavelength of 1.3 μm or longer depending on the In composition and nitrogen composition with GaInNAs. .

Further, regarding Ga _x In _1-x N _y As _1-y (0 ≦ x ≦ 1, 0 ≦ y <1), which is a strained quantum well layer, PL (Photoluminescence of GaInAs when no nitrogen is contained. Since the wavelength is longer than 1.12 μm, crystal growth of a material having a composition wavelength that could not be used for the light emitting layer of the conventional semiconductor light emitting device (semiconductor laser) allows the semiconductor light emitting device ( The degree of freedom in designing the (semiconductor laser) structure can be expanded. Specifically, in GaInAs with y = 0, by setting the In composition to 30% or more, a semiconductor light emitting device (semiconductor laser) having a wavelength longer than the conventional limit of 1.1 μm can be obtained. By setting the composition to 30% or more, the composition of nitrogen can be reduced as compared with the prior art. For example, in the case of obtaining a 1.3 μm band, the nitrogen composition can be made 1% or less.

  Further, in the semiconductor light emitting device (semiconductor laser) of FIG. 1, the nitrogen composition in the group V element of the strained quantum well layer 2 is in the range of 0 to 1%, and the nitrogen composition is in the small range of 0 to 1%. If this is the case, the decrease in crystallinity can be suppressed, so that a high-performance long wavelength band semiconductor light emitting device (semiconductor laser) can be obtained.

  In the semiconductor light emitting device (semiconductor laser) of FIG. 1, the plane orientation of the semiconductor substrate 1 is within a range of an inclination angle of 5 ° from (100), and the plane orientation of the semiconductor substrate is greatly tilted from (100). (For example, it is more inclined in the [011] direction), it is easier to increase the In composition of GaInNAs and GaInAs in the strained quantum well in the vicinity of (100), and it is suitable for longer wavelengths, and further improves the luminous efficiency. Since it is easy to make it high, it is suitable for a substrate of a highly strained quantum well semiconductor light emitting device (semiconductor laser).

  Further, in the semiconductor light emitting device (semiconductor laser) of FIG. 1, GaInP or GaInPAs is used as the cladding layer 4, and GaInP or GaInAs not containing Al can obtain a good crystal at a lower growth temperature than AlGaAs. Therefore, it is preferable in the case of manufacturing a high strain quantum well laser in which low temperature growth is preferable, and it is easy to obtain a high strain quantum well layer having good crystallinity.

In addition, when the semiconductor light emitting device (semiconductor laser) of FIG. 1 is a surface emitting type, a long wavelength band semiconductor light emitting device (semiconductor laser) can be formed on a GaAs substrate and has a large refractive index difference. Since a GaAs multilayer mirror can be used, a thin thickness is sufficient, and Al _x O _y obtained by oxidizing AlAs can be used for current narrowing. It is extremely effective compared to a light emitting element (semiconductor laser).

  Further, in the semiconductor light emitting device (semiconductor laser) of FIG. 1, the active layer 3 has a barrier layer (well layer strain compensated for stress) in the vicinity of the strained quantum well layers 2a and 2b, as shown in FIG. The strain compensation layers 5a, 5b, and 5c are formed. If there is a strain compensation layer that relaxes strain in the well layer, the quality of the well layer can be improved and the number of well layers can be increased. The design range of the semiconductor light emitting device (semiconductor laser) can be increased, and it is effective to have an optimum structure for high performance.

  In a method for manufacturing a semiconductor light emitting device (semiconductor laser) having an active layer 3 including a strained quantum well layer 2 and a clad layer 4 that confines light and carriers on a semiconductor substrate 1, the strained quantum well layer 2 is formed at a low temperature. In particular, low temperature growth at a temperature of 600 ° C. or lower is suitable for the growth of a high strain quantum well layer in which the strain amount exceeds 2%.

  In the case of a semiconductor light emitting device (semiconductor laser) formed of a III-V group semiconductor, the semiconductor light emitting device is formed by a metal organic vapor phase growth method using an organometallic compound as a group III material. That is, the metal organic vapor phase growth method is a growth method having a high degree of supersaturation, and is effective for growing a high strained quantum well layer or a material such as GaInNAs containing nitrogen in the V group.

Further, when the strained quantum well layer 2 is formed of Ga _x In _1-x N _y As _1-y (0 ≦ x ≦ 1, 0 ≦ y <1), DMHy (dimethylhydrazine), MMHy is used as a raw material of N It is formed using an organic nitrogen compound such as (monomethylhydrazine). That is, since organic nitrogen compounds decompose at low temperatures, they are suitable for low temperature growth at 600 ° C. or lower. Further, when a quantum well layer having a particularly large strain is grown as in the present invention, for example, low temperature growth of about 500 ° C. to 600 ° C. is preferable, and an organic nitrogen compound that decomposes at a low temperature is also preferable from this viewpoint.

  As described above, GaInAs on a GaAs substrate can increase the oscillation wavelength of a semiconductor light emitting device (semiconductor laser) by increasing the In composition, but it also increases the amount of distortion. The limit distortion is about 2%, and the oscillation wavelength is said to be 1.1 μm (refer to the document “IEEEPhotonics. Technol. Lett. Vol.9 (1997) pp.1319-1321”). .

  When a material having a different lattice constant is grown on the underlying substrate, the lattice elastically deforms and absorbs its energy. However, when a material having a different lattice constant is grown thicker than the underlying substrate, the strain energy cannot be absorbed only by elastic deformation, and misfit dislocation occurs. This film thickness is called critical film thickness. If misfit dislocations occur, it is difficult to produce a good device.

Theoretically, the critical film thickness (h _c ), which is the thickness at which misfit dislocations are generated mechanically, is given by the following equation according to Matthews and Blakeslee (reference “J. Crystal Growth. 27 (1974) 118.”). It has been.

Here, ν is a Poisson's ratio (ν = C ₁₂ / (C ₁₁ + C ₁₂ ); C ₁₁ and C ₁₂ are elastic stiffness constants), and α is an angle formed by a Burgers vector and a dislocation line segment at the interface. (Cos α = 1/2), λ is an angle (cos λ = 1/2) formed by the Burgers vector and the direction in the interface perpendicular to the intersecting line between the sliding surface and the interface, b = a / 2 ^1/2 (A: lattice constant), f is the degree of lattice mismatch (f = Δa / a). Equation (1) is an equation for growing a single layer film on an infinitely thick substrate. Hereinafter, the critical film thickness h _c given by this equation (Equation 1) is expressed by Matthews and Blakeslee's theory. This is called the critical film thickness.

FIG. 14 shows the critical film thickness of the GaInAs layer on the GaAs substrate calculated based on the generally supported Matthews and Blakeslee theory. Note that the lattice constant of Ga _1-x In _x NAs obtained by adding nitrogen to Ga _1-x In _x As is Ga _1-y In _y As (y = x) where the In composition x is 3% smaller per 1% of nitrogen addition. The lattice constant is almost the same as that of -0.03).

  When GaInAs is formed on a GaAs substrate, the amount of strain increases as the In composition increases, so that the critical film thickness, which is a film that can be grown two-dimensionally on a plane, becomes thinner.

On the other hand, the inventors of the present application can grow the strain amount of the quantum well layer with respect to the GaAs substrate by 2% or more by setting the In composition to a value exceeding 30% in the GaInAs quantum well layer on the GaAs substrate. It has been found that a semiconductor light emitting device (semiconductor laser) having a wavelength longer than 1.1 μm, which has been considered the limit, can be realized. Further, in the strained quantum well layer 2, the substantial critical film thickness h _c ′ can be made to exceed the critical film thickness h _c of Matthews and Blakeslee by growth under non-equilibrium conditions such as low temperature growth. Thus, it was found that a semiconductor light emitting device (semiconductor laser) having a long wavelength exceeding 1.2 μm can be realized.

That is, the inventor of the present application provides a semiconductor light emitting device in which an active layer including a strained quantum well layer and a cladding layer for confining light and carriers are formed on a semiconductor substrate. If the thickness of the well layer is thicker than the critical thickness _{h c} based on the theory of Matthews and Blakeslee, it is possible to obtain a semiconductor light-emitting element such as a semiconductor laser of the prior art is not obtained wavelength, also, high-performance HEMT conventionally It has been found that an electronic device such as (high electron mobility transister) can be obtained.

FIG. 14 shows an experimental example. Referring to FIG. 14, for example, when the In composition is 32% and the thickness is 8.6 nm, the PL center wavelength is 1.13 μm, and when the In composition is 36% and the thickness is 7.8 nm, the PL center wavelength is When the In composition was 39% and the thickness was 7.2 nm, the PL center wavelength was 1.2 μm. These are thicknesses exceeding the critical film thickness h _c calculated based on the theory of Matthews and Blakeslee (Equation 1).

FIG. 15 shows the relationship between the PL center wavelength and the PL intensity from the GaInAs single quantum well layer. The In composition x of the GaInAs well layer (solid line portion in the figure) was 31% to 42%. The thickness of each well layer 25a, 25b was reduced to about 9 nm to about 6 nm in accordance with the increase of the In composition x. A quantum well layer having a strong PL intensity up to a wavelength of about 1.2 μm was obtained. It can be seen that the PL intensity gradually decreases up to a wavelength of 1.2 μm, whereas the PL intensity rapidly decreases beyond 1.2 μm. This also corresponds to the surface property, and was a mirror surface up to 1.2 μm. From these results, it is considered that the sudden decrease in the PL intensity is due to the fact that the thickness of the quantum well layer exceeds the substantial critical film thickness h _c ′. In general, it has been reported that the critical film thickness obtained experimentally increases in MOCVD or MBE under strong non-equilibrium growth conditions such as low temperature growth and high growth rate. It has also been reported that, depending on the growth conditions (for example, high-temperature growth), three-dimensional growth and surface roughness occur even when the thickness is less than the critical thickness based on theory. Thus, the present results, the thicker the better substantial critical thickness h _c 'by growth in non-equilibrium conditions of the low-temperature growth such than the critical film thickness h _c based on theory without misfit dislocations occurs, It is considered that a thicker film could be grown in two dimensions.

  Furthermore, the inventors of the present application have found that, in the case of a GaInNAs laser, since the nitrogen composition can be reduced by increasing the In composition x as described above, the characteristics of the GaInNAs laser can be greatly improved.

  In addition, it has been found that when using laser, GaInP (As) can be formed more easily than using AlGaAs as the cladding layer. The reason is as follows.

That is, a GaInNAs or GaInAs active layer having a large strain can be grown at a low temperature (for example, 600 ° C. or less). However, the growth temperature of AlGaAs is generally high (eg, 700 ° C. or higher). The inventor of the present application conducted a heat treatment experiment on the assumption that an AlGaAs cladding layer is grown on the active layer after the active layer is grown. Specifically, four samples were sequentially grown on a (100) GaAs substrate with a GaAs layer (film thickness 0.2 μm), a GaInNAs well layer (film thickness 7 nm), and a GaAs layer (film thickness 50 nm). Samples (a, b, c, d) were prepared. The four samples a, b, c, and d have the same In composition and different nitrogen compositions. That is, the nitrogen (N) composition of sample a is 0.2%, the nitrogen (N) composition of sample b is 0.2%, and the nitrogen (N) composition of sample c is 0.5%, Sample d has a nitrogen (N) composition of 0.8%. Thereafter, in an AsH ₃ atmosphere using an MOCVD growth apparatus, the samples c and d were at a temperature of 680 ° C., the sample b was at a temperature of 700 ° C., and the sample a was at a temperature of 780 ° C. Heat treated (annealed) for 30 minutes. FIG. 12 shows the PL characteristics of these samples a, b, c, and d. In FIG. 12, the dotted line is the spectrum before the heat treatment, and the solid line is the spectrum after the heat treatment. It can be seen that the peak wavelength is shifted to the short wavelength side by the heat treatment, and the shift amount is larger as the heat treatment temperature is higher. At the same temperature, the shift amount is the same between samples with different amounts of nitrogen (sample c and sample d), and the cause of this shift is considered to be the diffusion of In. It can also be seen that the emission intensity decreases at 780 ° C. and increases at 700 ° C. or lower. The cause of the increase in emission intensity is considered to be a decrease in defects in the active layer due to heat treatment, and the cause of the decrease is considered to be deterioration of crystallinity.

  It has been found that when a GaInNAs or GaInAs active layer having such a large strain is grown, an upper layer (for example, a clad layer) is grown at a high temperature such as 780 ° C. For this reason, GaInP (As), which can be favorably grown at a low temperature, is preferable as the upper cladding layer. However, AlGaAs can be used because there is no major problem if it is grown at a temperature of 700 ° C. or lower.

Another reason is that if the AlGaAs is grown before the GaInNAs or GaInAs active layer having a large strain is grown, the quality of the active layer is easily deteriorated. The inventor of the present application has a guide layer (film thickness of 0.2 μm), a GaAs layer (film thickness of 100 nm), a GaInNAs well layer (film thickness of 7 nm), a GaAs layer (film thickness of 100 nm) and a guide layer (film thickness of 50 nm) were sequentially grown to prepare two samples. The first sample uses Ga _0.5 In _0.5 P as the guide layer (cladding layer) (hereinafter referred to as a sample using GaInP), and the second sample uses Al _0.4 Ga as the guide layer (cladding layer). _0.6 As was used (hereinafter referred to as a sample using AlGaAs). A sample using GaInP has a larger In composition and a larger strain. FIG. 13 shows the PL characteristics of the first sample (GaInP) and the second sample (AlGaAs). From FIG. 13, it can be seen that the sample using GaInP has a larger distortion than the sample using AlGaAs, although the distortion is longer and the wavelength is longer and the growth is difficult.

  As a cause of this, it is considered that defects caused by Al appear on the growth surface during growth, always propagate to the growth surface, reach the GaInNAs well layer, and deteriorate the well layer. In other words, it was found that the epitaxial substrate surface just before the growth of the quantum well active layer cannot be grown with high quality unless the surface state is good. For this reason, when AlGaAs is used as the lower cladding layer, it is necessary to devise a means to stop this defect before the well layer growth. When GaInP (As) containing no Al is used as the cladding layer between the semiconductor substrate and the active layer, the state of the epi-substrate surface immediately before the growth of the quantum well active layer is good, and a large strained quantum well layer can be easily formed. Can grow well. As described above, it is understood that GaInP (As) is preferably used as the cladding layer, particularly as the lower cladding layer between the semiconductor substrate and the active layer having a large strain.

Furthermore, the inventor of the present application indicates that the plane orientation of the GaAs substrate is more in the vicinity of (100) than in the case where the plane orientation is greatly inclined from (100) (for example, it is greatly inclined in the [011] direction from (100)). It has been found that the In composition is easily increased and the light emission efficiency is easily increased. One method for obtaining high-quality GaInNAs at a long wavelength such as the 1.3 μm band used in optical communication is to increase the In composition to increase the wavelength and reduce the nitrogen composition in GaInNAs. In each of the case where the plane orientation of the GaAs substrate is (100) and the case where the plane orientation of the substrate is inclined at an angle of 15 ° from the (100) direction to the [011] direction, Ga is formed on the GaAs substrate. _{From 0.5} In _0.5 P layer (film thickness is 0.2 μm), GaAs layer (film thickness is 100 nm), GaInNAs quantum well layer (light emitting layer) (film thickness is 7 nm) and GaAs barrier layer (film thickness is 13 nm) An active layer, a GaAs layer (with a film thickness of 100 nm), a Ga _0.5 In _0.5 P layer (with a film thickness of 50 nm), and a GaAs layer (with a film thickness of 50 nm) were sequentially formed. FIG. 3 shows a PL characteristic (indicated by reference symbol A) of a semiconductor light emitting device formed on a GaAs substrate having a plane orientation of (100) and an angle of 15 ° from the (100) to the [011] direction. 2 shows PL characteristics (indicated by symbol B) of a semiconductor light emitting device formed on a GaAs substrate tilted by. Note that in a semiconductor light emitting device formed on a GaAs substrate whose plane orientation is inclined at an angle of 15 ° from the (100) direction to the [011] direction, nitrogen is added to GaInAs having a PL wavelength of 1.06 μm. On the other hand, in a semiconductor light emitting device formed on a GaAs substrate having a plane orientation of (100), nitrogen is added to GaInAs having a PL wavelength of 1.13 μm.

  As can be seen from FIG. 3, the semiconductor light emitting device formed on the GaAs substrate having the plane orientation of (100) has a higher light emission intensity despite the longer wavelength and is more suitable. In contrast, in a semiconductor light emitting device formed on a GaAs substrate whose plane orientation is inclined at an angle of 15 ° from the (100) direction to the [011] direction, the In composition is increased and the wavelength is longer than the wavelength of 1.06 μm. However, it was difficult to increase the In composition. On the other hand, in a semiconductor light emitting device formed on a GaAs substrate having a plane orientation of (100), strong light emission was observed up to a wavelength of about 1.2 μm using GaInAs. For this reason, it is preferable that the inclination angle of the plane orientation of the GaAs substrate from (100) is within a range of 5 °.

  Next, examples will be described.

4 is a diagram showing a semiconductor light emitting device of Example 1. FIG. Here, an insulating film stripe type laser having the simplest structure will be described as an example of the semiconductor light emitting element. The semiconductor light emitting device of FIG. 4 has a SCH-DQW (Separate Confinement Heterostructure Double Quantum Well) structure as a layer structure. Specifically, the semiconductor light emitting device of FIG. 4 has an n-GaAs buffer layer 22 and an n-GaInP (As) lower cladding layer 23 (with a film thickness of 1.. 5 μm), a GaAs light guide layer 24 (film thickness is 100 nm), an active layer (light emitting layer) 27 composed of Ga _1-x In _x As well layers 25 a and 25 _b and a GaAs barrier layer 26 (film thickness is 13 nm), , A GaAs light guide layer 28 (film thickness is 100 nm), a p-GaInP (As) upper cladding layer 29 (film thickness is 1.5 μm), and a p-GaAs contact layer 30 (film thickness is 0.3 μm). Are formed sequentially. Further, in the semiconductor light emitting device of FIG. 4, the GaAs contact layer 30 is removed by etching except for the current injection portion, and the p-side electrode 32 is formed through the insulating film 31 from which the portion to be the current injection portion is removed. An n-side electrode 33 is formed on the back surface of the substrate 21.

Here, the In composition x of the Ga _1-x In _x As well layers 25a and 25b was 31% to 42%. The thickness of each well layer 25a, 25b was reduced to about 9 nm to about 6 nm in accordance with the increase in In composition. The quantum well layer thicknesses of these lasers has a thicker conditions than the critical film thickness _{h c} based on the theory of Matthews and Blakeslee. For example, when the In composition is 32% and the thickness is 8.6 nm, the oscillation wavelength is 1.13 μm, and when the In composition is 36% and the thickness is 7.8 nm, the oscillation wavelength is 1.16 μm. When the In composition was 39% and the thickness was 7.2 nm, the oscillation wavelength was 1.2 μm. Moreover, the amount of compressive strain of each well layer 25a, 25b varied depending on the composition, and was about 2.2% to 2.7%.

The growth method of each layer of the semiconductor light emitting device of FIG. 4 was performed by MOCVD. TMG (trimethylgallium), TMI (trimethylindium), AsH ₃ (arsine), and PH ₃ (phosphine) were used as the raw material, and H ₂ was used as the carrier gas. The GaInAs layer was grown at 550 ° C.

FIG. 5 shows the threshold current density J _th with respect to the oscillation wavelength of the semiconductor light emitting device of FIG. From FIG. 5, the oscillation wavelength of the semiconductor light emitting device of FIG. 4 is 1.13 to 1.23 μm, and the oscillation wavelength can be made longer than that of a GaInAs quantum well laser device grown on a conventional GaAs substrate. I understand. In addition, when the oscillation wavelength exceeds 1.2 μm, the threshold value suddenly rises. However, until about 1.2 μm, the threshold current density J _th is about 200 A / cm ² and is sufficiently low. Also, the characteristics at high temperature were good.

  In the above example, the semiconductor light emitting device is grown by the MOCVD method, but other growth methods such as the MBE method can also be used. In the semiconductor light emitting device of FIG. 4, an example of a double quantum well structure (DQW) is shown as the stacked structure of the active layer (light emitting layer), but a structure using quantum wells having other numbers of wells (SQW, MQW) can also be used. The composition thickness of each layer can be changed and set as necessary. Further, the wide gap AlGaAs similar to GaInP (As) can be used for the cladding layer. Also, the structure of the laser may be another structure. However, the surface orientation of the GaAs substrate is preferably in the vicinity of (100), and the inclination angle of the surface orientation from (100) is preferably within a range of 5 °. Further, when GaInP is grown on a (100) substrate having a plane orientation (100) or slightly inclined by MOCVD or the like, a hill-like defect called hillock is likely to be formed. This is undesirable because it adversely affects device yield and light emission efficiency. Although the hillock density can be reduced by optimizing the growth conditions, it can be easily reduced by using GaInPAs containing As. The As composition is preferable because it has a slight effect.

6 is a view showing a semiconductor light emitting device of Example 2. FIG. Here, an insulating film stripe type laser having the simplest structure will be described as an example of the semiconductor light emitting element. The semiconductor light emitting device of FIG. 6 has an SCH-DQW (Separate Confinement Heterostructure Double Quantum Well) structure as a layer structure. Specifically, the semiconductor light emitting device of FIG. 6 has an n-GaAs buffer layer 42 and an n-GaInP (As) lower cladding layer 43 (with a film thickness of 1.. 5 μm), a GaAs light guide layer 44 (film thickness is 100 nm), an active layer (light emitting layer) 47 comprising Ga _0.67 In _0.33 N _0.006 As _0.994 well layers 45a and 45b and a GaAs barrier layer 46 (film thickness is 13 nm). GaAs light guide layer 48 (film thickness is 100 nm), p-GaInP (As) upper cladding layer 49 (film thickness is 1.5 μm), p-GaAs contact layer 50 (film thickness is 0.3 μm), Are sequentially formed. In the semiconductor light emitting device of FIG. 6, the GaAs contact layer 50 is removed by etching except for the current injection portion, and the p-side electrode 52 is formed through the insulating film 51 from which the portion to be the current injection portion is removed. An n-side electrode 53 is formed on the back surface of the substrate 41.

  Here, the In composition x of each well layer 45a, 45b was 33%, and the nitrogen (N) composition was 0.6%. The thickness of each well layer 45a, 45b was 7 nm. Further, the amount of compressive strain of each of the well layers 45a and 45b was about 2.3%.

The growth method of each layer of the semiconductor light emitting device of FIG. 6 was performed by MOCVD. TMG (trimethylgallium), TMI (trimethylindium), AsH ₃ (arsine), and PH ₃ (phosphine) were used as the raw material, and DMHy (dimethylhydrazine) was used as the nitrogen raw material. DMHy decomposes at low temperatures and is therefore suitable for low temperature growth at 600 ° C. or lower. In particular, when a quantum well layer having a large strain is grown, a low temperature growth of, for example, about 500 ° C. to 600 ° C. is preferable. That is, since DMHy decomposes at a low temperature, it is suitable for a low temperature growth of 600 ° C. or lower, and is particularly preferable when a quantum well layer having a large strain required for low temperature growth is grown. In the present example, the GaInNAs well layers 45a and 45b were grown at 550 ° C. Further, H ₂ was used as a carrier gas.

FIG. 7 shows current-output power (voltage) characteristics in the continuous operation of the semiconductor light emitting device of FIG. Here, the threshold current density J _th was 570 A / cm ² . The oscillation wavelength was about 1.24 μm. In the semiconductor light emitting device of FIG. 6, the threshold current density J _th is higher than that of the conventional GaInNAs laser device by making the In composition of the well layers 45a and 45b larger than 30% and the compressive strain amount being 2% or more. Was dramatically reduced. Also, the characteristics at high temperature were good. The oscillation wavelength is variable by controlling the nitrogen composition, the In composition, the thickness of the well layer, and the like.

In the above example, the semiconductor light emitting device is grown by MOCVD, but other growth methods such as MBE can be used. In the semiconductor light emitting device of FIG. 6, DMHy is used as the material for nitrogen (N) in the well layers 45a and 45b, but other nitrogen compounds such as activated nitrogen and NH ₃ can also be used. In the semiconductor light emitting device of FIG. 6, an example of a double quantum well structure (DQW) is shown as a stacked structure of active layers (light emitting layers), but a structure using quantum wells having other numbers of wells (SQW, MQW). ) Can also be used. The composition thickness of each layer can be changed and set as necessary. Further, the wide gap AlGaAs similar to GaInP (As) can be used for the cladding layer. Also, the structure of the laser may be another structure.

  FIG. 8 is a view showing a semiconductor light emitting device of Example 3. Here, an insulating film stripe type laser having the simplest structure will be described as an example of the semiconductor light emitting element. The semiconductor light emitting device of FIG. 8 has an SCH-DQW (Separate Confinement Heterostructure Double Quantum Well) structure as a layer structure. The semiconductor light emitting device of FIG. 8 of Example 3 has substantially the same structure as that of FIG. 6 of Example 2, but the plane orientation of the n-GaAs substrate 41 is 2 ° from the (100) to the [011] direction. It is tilted at an angle. Further, the composition of the well layer is different from that of Example 2.

That is, the semiconductor light emitting device of FIG. 8 has an n-GaAs buffer layer 62 and an n-GaInP (As) on an n-GaAs substrate 61 whose plane orientation is inclined at an angle of 2 ° from the (100) direction to the [011] direction. ) Lower cladding layer 63 (film thickness is 1.5 μm), GaAs light guide layer 64 (film thickness is 100 nm), Ga _0.6 In _0.4 N _0.005 As _0.995 well layers 65a and 65b, and GaAs barrier layer 66 (film thickness is 13 nm) active layer (light emitting layer) 67, GaAs light guide layer 68 (film thickness is 100 nm), p-GaInP (As) upper clad layer 69 (film thickness is 1.5 μm), p-GaAs contact Layers 70 (film thickness is 0.3 μm) are sequentially formed. Further, in the semiconductor light emitting device of FIG. 8, the GaAs contact layer 70 is removed by etching except for the current injection portion, and the p-side electrode 72 is formed via the insulating film 71 from which the portion to be the current injection portion is removed. An n-side electrode 73 is formed on the back surface of the substrate 61.

Here, the In composition x of each well layer 65a, 65b was 40%, and the nitrogen (N) composition was 0.5%. The thickness of each well layer 65a, 65b was 7 nm. This is a condition thicker than the critical film thickness h _c (about 6.1 nm) based on the theory of Matthews and Blakeslee. Further, the amount of compressive strain of each of the well layers 65a and 65b was about 2.7%.

The growth method of each layer of the semiconductor light emitting device of FIG. 8 was performed by MOCVD. TMG (trimethylgallium), TMI (trimethylindium), AsH ₃ (arsine), and PH ₃ (phosphine) were used as the raw material, and DMHy (dimethylhydrazine) was used as the nitrogen raw material. DMHy decomposes at low temperatures and is therefore suitable for low temperature growth at 600 ° C. or lower. In particular, when a quantum well layer having a large strain is grown, a low temperature growth of about 500 ° C. to 600 ° C. is preferable, for example. In the present example, the GaInNAs well layers 65a and 65b were grown at 540 ° C. Further, H ₂ was used as a carrier gas.

The oscillation wavelength of the semiconductor light emitting device of FIG. 8 produced in this way was about 1.3 μm. The threshold current density J _th was 1 kA / cm ² or less. In GaInNAs lasers, the threshold current density tends to increase as the nitrogen composition increases. In the conventional 1.3 μm GaInNAs laser element, the nitrogen composition was 1% at the minimum (when the In composition was 30%). However, in the present invention, the In composition is made larger than 30% to compress the strain. By making the amount 2% or more, the nitrogen composition can be made smaller than before, and the threshold current density can be dramatically reduced. Also, the characteristics at high temperature were good.

In the above example, the semiconductor light emitting device is grown by MOCVD, but other growth methods such as MBE can be used. In the semiconductor light emitting device of FIG. 8, DMHy is used as the nitrogen (N) material of the well layers 65a and 65b, but other nitrogen compounds such as activated nitrogen and NH ₃ can also be used. In the semiconductor light emitting device of FIG. 8, the example of the double quantum well structure (DQW) is shown as the stacked structure of the active layer (light emitting layer), but the structure using the quantum wells having other numbers of wells (SQW, MQW). ) Can also be used. The composition thickness of each layer can be changed and set as necessary. Further, the wide gap AlGaAs similar to GaInP (As) can be used for the cladding layer. Also, the structure of the laser may be another structure.

FIG. 9 is a diagram showing a semiconductor light emitting device of Example 4. Here, an insulating film stripe type laser having the simplest structure will be described as an example of the semiconductor light emitting element. The semiconductor light emitting device of FIG. 9 has a SCH-DQW (Separate Confinement Heterostructure Double Quantum Well) structure as a layer structure. Specifically, the semiconductor light emitting device of FIG. 9 has an n-GaAs buffer layer 82, an n-GaInP on an n-GaAs substrate 81 whose plane orientation is inclined at an angle of 5 ° from the (100) direction to the [011] direction. (As) The lower cladding layer 83 (thickness is 1.5 μm), the GaAs light guide layer 84 (thickness is 100 nm), Ga _0.65 In _0.35 N _0.007 As _0.993 well layers 85a and 85b, and well layers 85a and 85b. An active layer (light emitting layer) 87 formed with GaNPAs barrier layers 86a, 86b, 86c (each film thickness is 10 nm) provided between and below the well layer 85a and above the well layer 85b, and a GaAs light guide A layer 88 (with a film thickness of 100 nm), a p-GaInP (As) upper cladding layer 89 (with a film thickness of 1.5 μm), and a p-GaAs contact layer 90 (with a film thickness of 0.3 μm) are sequentially formed. ing. Further, in the semiconductor light emitting device of FIG. 9, the GaAs contact layer 90 is removed by etching except for the current injection portion, and the p-side electrode 92 is formed through the insulating film 91 from which the portion to be the current injection portion is removed. An n-side electrode 93 is formed on the back surface of the substrate 91.

  Here, the In composition x of each of the well layers 85a and 85b was 35%, and the nitrogen (N) composition was 0.7%. The thickness of each well layer 85a, 85b was 7 nm. The compressive strain amount of each well layer 85a and 85b was about 2.4%. At this time, the barrier layers 86a, 86b, 86c have tensile strain, and alleviate the compression of the well layers 85a, 85b.

The growth method of each layer of the semiconductor light emitting device of FIG. 9 was performed by MOCVD. TMG (trimethylgallium), TMI (trimethylindium), AsH ₃ (arsine), and PH ₃ (phosphine) were used as the raw material, and DMHy (dimethylhydrazine) was used as the nitrogen raw material. DMHy decomposes at low temperatures and is therefore suitable for low temperature growth at 600 ° C. or lower. In particular, when a quantum well layer having a large strain is grown, a low temperature growth of about 500 ° C. to 600 ° C. is preferable, for example. In the present example, the GaInNAs layer was grown at 520 ° C. Further, H ₂ was used as a carrier gas.

The oscillation wavelength of the semiconductor light emitting device of FIG. 9 manufactured in this way was about 1.3 μm. The threshold current density J _th was 1 kA / cm ² or less. In GaInNAs lasers, the threshold current density tends to increase as the nitrogen composition increases. In a conventional 1.3 μm band GaInAs laser element, the nitrogen composition was 1% at the minimum (when the In composition was 30%). However, in the present invention, the In composition is made larger than 30% and the compressive strain is increased. By making the amount 2% or more, the nitrogen composition can be made smaller than before, and the threshold current density can be dramatically reduced. Furthermore, in Example 4, since the barrier layers 86b and 86c having tensile strain that relieve the compressive strain of the well layers 85a and 85b are further provided, the threshold current density is reduced as compared with the element of Example 3. Also, the characteristics at high temperature were good.

In the above example, the semiconductor light emitting device is grown by MOCVD, but other growth methods such as MBE can be used. In the semiconductor light emitting device of FIG. 9, DMHy is used as the nitrogen (N) material for the well layers 85a and 85b, but other nitrogen compounds such as activated nitrogen and NH ₃ can also be used. In the semiconductor light emitting device of FIG. 9, an example of a double quantum well structure (DQW) is shown as a stacked structure of active layers (light emitting layers), but a structure using quantum wells with other numbers of wells (SQW, MQW). ) Can also be used. The composition thickness of each layer can be changed and set as necessary. Further, the wide gap AlGaAs similar to GaInP (As) can be used for the cladding layer. Also, the structure of the laser may be another structure.

  FIG. 10 is a diagram showing a semiconductor light emitting device (semiconductor laser) of Example 5. The semiconductor light emitting element shown in FIG. 10 is a surface emitting type. Since this semiconductor light emitting device constitutes a resonator for obtaining light emission, an upper reflecting mirror 109 is formed on the opposite side of the quantum well active layer 104 to the semiconductor substrate 101, and the quantum well active layer 104 A lower reflecting mirror 102 is formed on the semiconductor substrate 101 side, and at least the lower reflecting mirror 102 of the upper reflecting mirror 109 and the lower reflecting mirror 102 is composed of a low refractive index layer and a high refractive index layer made of a material not containing Al. Are configured as a semiconductor multilayer film alternately stacked. In this configuration, the upper reflecting mirror 109 and the lower reflecting mirror 102 function as resonators for light emission from the quantum well active layer 104.

More specifically, the semiconductor light emitting device of FIG. 10 includes n-Ga _0.5 In _0.5 P and n-GaAs lattice-matched to the GaAs substrate 101 on the n-GaAs substrate 101 having the plane orientation (100) in each medium. N-semiconductor multilayer mirror (GaInP / GaAs lower semiconductor multilayer mirror) 102, GaAs spacer layers 103, 3 having a periodic structure (35 periods) stacked alternately with a thickness of 1/4 of the oscillation wavelength in FIG. Multi-quantum well active layer (GaInNAs / GaAs QW active layer) 104 consisting of Ga _0.6 In _0.4 N _0.005 As _0.995 As well layer and GaAs barrier layer (13 nm), GaAs spacer layer 105, Al _x O _y current narrowing layer 106 , P-AlAs layer 107 (film thickness is 50 nm) as a current injection part, p-GaAs contact layer 108, and p-Ga lattice matched to GaAs substrate 101 P-semiconductor multilayer reflector (GaInP / GaAs upper semiconductor) having a periodic structure (30 periods) in which _0.5 In _0.5 P and p-GaAs are alternately stacked with a thickness of 1/4 times the oscillation wavelength in each medium. A multilayer reflector 109) is sequentially grown.

  An insulating film (polyimide) 110 is formed on the side surfaces of the GaAs spacer layer 103, the quantum well active layer 104, the GaAs spacer layer 105, the current narrowing layer 106, and the p-GaAs contact layer 108. A p-side electrode 111 is formed on the p-GaAs contact layer 108, and an n-side electrode 112 is formed on the back surface of the GaAs substrate 101.

The semiconductor light emitting device of FIG. 10 was produced as follows. That is, first, n-Ga _0.5 In _0.5 P and n-GaAs lattice-matched to the GaAs substrate 101 on the n-GaAs substrate 101 having the plane orientation (100) are ¼ times the oscillation wavelength in each medium. N-semiconductor multilayer reflector (GaInP / GaAs lower semiconductor multilayer reflector) 102 having a periodic structure (35 periods) stacked alternately by thickness, GaAs spacer layer 103, and three layers of Ga _0.6 In _0.4 N _0.005 As _0.995 Multiple quantum well active layer (GaInNAs / GaAs QW active layer) 104 composed of an As well layer and a GaAs barrier layer (13 nm), a GaAs spacer layer 105, an Al _x O _y current narrowing layer 106, and p-AlAs as a current injection portion layer 107 (film thickness 50 nm), lattice-matched to the p-GaAs contact layer 108, GaAs substrate 101 p-Ga _0.5 in _0.5 P and p-Ga A p-semiconductor multilayer mirror (GaInP / GaAs upper semiconductor multilayer mirror) 109 having a periodic structure (30 periods) in which s are alternately stacked with a thickness of 1/4 times the oscillation wavelength in each medium is provided. Grown sequentially.

Here, the In composition x of the well layer was 40%, and the nitrogen composition was 0.5%. The thickness of the well layer was 7 nm. This is a condition thicker than the critical film thickness h _c (about 6.1 nm) based on the theory of Matthews and Blakeslee. The amount of compressive strain was about 2.7%. The growth method was the MOCVD method. TMG (trimethylgallium), TMI (trimethylindium), AsH ₃ (arsine), PH ₃ (phosphine) were used as raw materials, and DMHy (dimethylhydrazine) was used as a raw material for nitrogen.

Since DMHy decomposes at low temperatures, it is suitable for low-temperature growth at 600 ° C. or lower. Moreover, when growing a quantum well layer with a large strain, a low temperature growth of about 500 ° C. to 600 ° C. is preferable, for example. In Example 5, the GaInNAs layer was grown at 540 ° C. Since DMHy decomposes at low temperatures, it is suitable for low temperature growth such as 600 ° C. or lower, and is particularly preferable when growing a quantum well layer having a large strain required for low temperature growth. Further, H ₂ was used as a carrier gas.

Then, mesa etching was performed in a circular shape having a diameter of 30 μm up to the upper portion of the lower multilayer film reflecting mirror 102 by photolithography and an etching process, and only the upper multilayer film reflecting mirror 109 was mesa etched in a circular shape having a diameter of 10 μm. The Al _x O _y current narrowing portion 106 was formed by oxidizing AlAs appearing on the side surface from the side surface with water vapor.

  Next, the etched portion is filled with an insulating film (polyimide) 110 and planarized, and the portion on which the p-side electrode 111 is to be formed and the polyimide on the upper multilayer mirror 109 serving as the light extraction port are removed, and p-GaAs is removed. A p-side electrode 111 was formed on the contact layer 108, and an n-side electrode 112 was formed on the back surface of the substrate 101.

  In the semiconductor light emitting device of FIG. 10, n-GaInP and n-GaAs not containing Al are used as the n-semiconductor multilayer reflector (lower semiconductor multilayer reflector) 102 between the semiconductor substrate 101 and the active layer 104. Therefore, the active layer 104 having a large strain could be easily grown without deteriorating.

  The lower semiconductor multilayer mirror 102 between the semiconductor substrate 101 and the active layer 104 does not contain Al, and a combination of a material having a large refractive index and a material having a small refractive index can be used. Specifically, in addition to the combination of GaInP (low refractive index layer) and GaAs (high refractive index layer), GaInPAs (low refractive index layer) and GaAs (high refractive index layer), GaInP (low refractive index layer) and GaInPAs ( High refractive index layer), GaInP (low refractive index layer) and GaPAs (high refractive index layer), GaInP (low refractive index layer) and GaInAs (high refractive index layer), GaInP (low refractive index layer) and GaInNAs (high refractive index) A combination such as a rate layer can be used. Of course, it is easier to grow an active layer having a large strain on the lower semiconductor multilayer film reflecting material using a material that does not contain Al, but even if a material containing Al is used. It can be used by optimizing the growth conditions. Specifically, a combination of AlAs (low refractive index layer) and GaAs (high refractive index layer), a combination of AlGaAs and GaAs, AlAs and AlGaAs, AlGaAs (large Al composition) and AlGaAs (low Al composition), etc. are used. be able to.

  Also, the upper semiconductor multilayer reflector 109 on the surface side of the active layer 104 (p-semiconductor multilayer reflector in this embodiment) does not contain Al and uses a combination of a material having a high refractive index and a material having a small refractive index. Can do. Specifically, in addition to the combination of GaInP (low refractive index layer) and GaAs (high refractive index layer), GaInPAs (low refractive index layer) and GaAs (high refractive index layer), GaInP (low refractive index layer) and GaInPAs ( High refractive index layer), GaInP (low refractive index layer) and GaPAs (high refractive index layer), GaInP (low refractive index layer) and GaInAs (high refractive index layer), GaInP (low refractive index layer) and GaInNAs (high refractive index) A combination such as a rate layer can be used.

However, the upper semiconductor multilayer reflector 109 (p-semiconductor multilayer reflector in this embodiment) on the surface side of the active layer 104 may contain Al. Specifically, a combination of AlAs (low refractive index layer) and GaAs (high refractive index layer), a combination of AlGaAs and GaAs, AlAs and AlGaAs, AlGaAs (large Al composition) and AlGaAs (low Al composition), etc. are used. be able to. In this case, since the active layer 104 having a large strain is grown at a low temperature, the active layer 104 is preferably grown at a temperature as low as possible (for example, 700 ° C. or lower). In addition, a dielectric multilayer film can be used as the upper semiconductor multilayer film reflecting mirror 109. Specifically, a combination of TiO ₂ and SiO ₂ can be used.

The surface emitting laser (semiconductor laser shown in FIG. 10) produced in this way had an oscillation wavelength of about 1.3 μm. The threshold current density was 1 kA / cm ² or less. By making the In composition larger than 30% and the compressive strain amount being 2% or more, the nitrogen composition can be made smaller than before, and the threshold current density can be dramatically reduced. The characteristics at high temperature were also good. It also had a long life.

In the fifth embodiment, an example of the growth by the MOCVD method is shown, but other growth methods such as the MBE method can also be used. Further, although DMHy is used as a nitrogen raw material, other nitrogen compounds such as activated nitrogen and NH ₃ can also be used.

  In the above example, an example of a triple quantum well structure (TQW) is shown as a stacked structure, but a structure using quantum wells with other numbers of wells (SQW, MQW) or the like can also be used. Further, the composition thickness of each layer can be set to other values as required. Further, GaInAs can be used for the active layer 104. The structure of the laser may be another structure.

  FIG. 11 is a diagram showing a semiconductor light emitting device (semiconductor laser) of Example 6. The semiconductor light emitting element shown in FIG. 11 is a surface emitting type. Since this semiconductor light emitting device constitutes a resonator for obtaining light emission, an upper reflecting mirror 128 is formed on the side of the quantum well active layer 123 opposite to the semiconductor substrate 121, and the quantum well active layer 123 A lower reflecting mirror 129 is formed on the semiconductor substrate 121 side, and at least the lower reflecting mirror 129 of the upper reflecting mirror 128 and the lower reflecting mirror 129 has a low refractive index layer and a high refractive index layer made of a dielectric material. It is configured as a dielectric multilayer film laminated alternately. Also in this configuration, the upper reflecting mirror 128 and the lower reflecting mirror 129 function as resonators for light emission from the quantum well active layer 123.

More specifically, the semiconductor light emitting device of FIG. 11 has an n-GaInPAs clad layer 122 (film thickness: 0.5 μm), 3 lattice-matched to the GaAs substrate 121 on the n-GaAs substrate 121 having a plane orientation (100). Multi-quantum well active layer (GaInNAs / GaAs) consisting of Ga _0.6 In _0.4 N _0.005 As _0.995 As well layer and GaAs barrier layer
QW active layer) 123, p-GaInPAs clad layer 124 (film thickness is 1.5 μm), Al _x O _y current narrowing layer 125, AlAs layer 126 (film thickness is 50 nm) as a current injection portion, p-GaAs contact layer 127 (thickness is 0.3 μm), p-semiconductor multilayer having a periodic structure (21 periods) in which p-AlAs and p-GaAs are alternately stacked at a thickness that is ¼ times the oscillation wavelength in each medium. A film reflector (AlGaAs / GaAs upper semiconductor multilayer reflector) 128 is sequentially grown. In the semiconductor light emitting device of FIG. 11, a part of the GaAs substrate 121 is etched to the surface of the cladding layer 122, and a dielectric multilayer reflector (TiO ₂ ) made of a combination of TiO ₂ and SiO ₂ is formed on the cladding layer 122. / SiO ₂ lower dielectric multilayer reflector) 129 is formed.

  An insulating film (polyimide) 130 is formed on the side surfaces of the current narrowing layer 125 and the p-GaAs contact layer 127, and a p-side electrode 131 is formed on the p-GaAs contact layer 127. An n-side electrode 132 is formed on the back surface of the substrate 121.

The semiconductor light emitting device of FIG. 11 was produced as follows. That is, first, an n-GaInPAs clad layer 122 (film thickness is 0.5 μm) lattice-matched to the GaAs substrate 121 and a three-layer Ga _0.6 In _0.4 N _0.005 As on the n-GaAs substrate 121 of the plane orientation (100). _0.995 Multiple quantum well active layer (GaInNAs / GaAs QW active layer) 123 composed of As well layer and GaAs barrier layer, p-GaInPAs clad layer 124 (thickness: 1.5 μm), Al _x O _y current narrowing layer 125, current An AlAs layer 126 (film thickness is 50 nm) as an injection portion, a p-GaAs contact layer 127 (film thickness is 0.3 μm), p-AlAs and p-GaAs are ¼ times the oscillation wavelength in each medium. A p-semiconductor multilayer reflector (AlGaAs / GaAs upper semiconductor multilayer reflector) 128 having a periodic structure (21 periods) stacked alternately with a thickness is sequentially grown. It was.

Here, the In composition x of the well layer was 40%, and the nitrogen composition was 0.5%. The thickness of the well layer was 7 nm. The amount of compressive strain was about 2.7%. The growth method was the MOCVD method. TMG (trimethylgallium), TMI (trimethylindium), AsH ₃ (arsine), PH ₃ (phosphine) were used as raw materials, and DMHy (dimethylhydrazine) was used as a raw material for nitrogen. The p-semiconductor multilayer mirror 128 containing Al was grown at a low temperature of 680 ° C., which has little influence on the active layer 123.

Then, mesa etching was performed in a circular shape with a diameter of 10 μm up to the upper portion of the p-semiconductor multilayer reflector 128 by photolithography and etching processes, and the p-GaAs contact layer 127 was further mesa-etched into a circular shape with a diameter of 30 μm. Then, an insulating film (polyimide) 130 was coated and the current injection portion 126 was opened to form the p-side electrode 131. Then, the semiconductor substrate 121 was etched until the surface of the n-GaInPAs clad layer 122 appeared to form a dielectric multilayer mirror 129 made of a combination of TiO ₂ and SiO ₂ . Further, an n-side electrode 132 was formed on the back surface of the substrate 121. In such a structure, the light extraction portion is the back surface of the substrate 121.

  In the sixth embodiment, the semiconductor multilayer film reflector is not inserted between the semiconductor substrate 121 and the active layer 123 having a large strain, and the dielectric multilayer film is used as the reflector on the substrate 121 side. The active layer 123 can be easily grown without deteriorating.

  In other words, the reflecting mirror on the semiconductor substrate side is formed outside the semiconductor portion, and the semiconductor layer containing Al is not formed between the semiconductor substrate and the quantum well active layer having a large strain. The state of the epi-substrate surface during growth was good, and a large strained quantum well layer could be easily and satisfactorily grown.

The surface emitting laser produced in this way had an oscillation wavelength of about 1.3 μm. The threshold current density was 1 kA / cm ² or less. By making the In composition larger than 30% and the compressive strain amount being 2% or more, the nitrogen composition can be made smaller than before, and the threshold current density can be dramatically reduced. The characteristics at high temperature were also good.

In the sixth embodiment, the example of the growth by the MOCVD method is shown, but other growth methods such as the MBE method can also be used. Further, although DMHy is used as a nitrogen raw material, other nitrogen compounds such as activated nitrogen and NH ₃ can also be used.

  In the above example, an example of a triple quantum well structure (TQW) is shown as a stacked structure, but a structure using quantum wells with other numbers of wells (SQW, MQW) or the like can also be used. Further, the composition thickness of each layer can be set to other values as required. Alternatively, GaInAs can be used for the active layer 123. The structure of the laser may be another structure.

  The quality of an active layer having such a large strain is very sensitive to the structure and growth conditions, and the present invention has been described in detail. Even if it is less than 2%, it is effective.

  In each of the above-described embodiments, when a GaAs substrate is used as the semiconductor substrate, an example in which GaInAs and GaInNAs are used as the semiconductor material on the GaAs substrate has been shown, but in addition to this, a GaAs substrate is used as the semiconductor substrate. When using GaInP, GaPAs as the semiconductor material on the GaAs substrate, or when using an InP substrate as the semiconductor substrate, such as when using GaInAs, GaInPAs, InPAs, InNPAs, etc. as the semiconductor material on the InP substrate. Also, the present invention can be applied. That is, the present invention is effective for a semiconductor light emitting device using a semiconductor having a lattice constant that is significantly different from that of the semiconductor substrate. The present invention can also be applied to semiconductor elements using III-V mixed crystal semiconductors such as other light emitting elements, light receiving elements or electronic elements.

The present invention can be used for a semiconductor light emitting element for optical communication, a light emitting diode, a photodiode for infrared light, and the like.

It is a figure which shows the structural example of the semiconductor light-emitting device based on this invention. It is a figure which shows an example of the active layer of the semiconductor light-emitting device of FIG. PL characteristics of a semiconductor light emitting device formed on a GaAs substrate having a plane orientation of (100) and a plane orientation of the semiconductor light emitting device inclined from the (100) to the [011] direction at an angle of 15 °. It is a figure which shows the PL characteristic of a semiconductor light-emitting device. 1 is a diagram showing a semiconductor light emitting device of Example 1. FIG. FIG. 5 is a diagram showing a threshold current density with respect to an oscillation wavelength of the semiconductor light emitting device of FIG. 4. 6 is a diagram showing a semiconductor light emitting device of Example 2. FIG. It is a figure which shows the current-voltage characteristic in the continuous operation | movement of the semiconductor light-emitting device of FIG. 6 is a view showing a semiconductor light emitting device of Example 3. FIG. 6 is a diagram showing a semiconductor light emitting device of Example 4. FIG. 6 is a diagram showing a semiconductor light emitting device of Example 5. FIG. 6 is a diagram showing a semiconductor light emitting device of Example 6. FIG. It is a figure which shows the PL characteristic of four samples a, b, c, and d. It is a figure which shows the PL characteristic of the sample which used GaInP as a guide layer, and the sample which used AlGaAs. It is a figure which shows the critical film thickness of the GaInAs layer on the GaAs substrate calculated based on the theory of Matthews and Blakeslee generally supported. It is a figure which shows the relationship between PL center wavelength and Ga intensity | strength from a GaInAs single quantum well layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 3 Active layer 2 Strained quantum well layer 4 Clad layer 5 Barrier layer 21 n-GaAs substrate 22 n-GaAs buffer layer 23 n-GaInP (As) lower clad layer 24 GaAs light guide layer 25a, 25b Ga _1-x In _x As quantum well layer 26 GaAs barrier layer 27 Active layer (light emitting layer)
28 GaAs light guide layer 29 p-GaInP (As) upper clad layer 30 p-GaAs contact layer 32 p-side electrode 31 insulating film 33 n-side electrode 41 n-GaAs substrate 42 n-GaAs buffer layer 43 n-GaInP (As) Lower cladding layer 44 GaAs optical guide layer 45a, 45b Ga _0.67 In _0.33 N _0.006 As _0.994 quantum well layer 46 GaAs barrier layer 47 active layer (light emitting layer)
48 GaAs light guide layer 49 p-GaInP (As) upper cladding layer 50 p-GaAs contact layer 52 p-side electrode 51 insulating film 53 n-side electrode 61 n-GaAs substrate 62 n-GaAs buffer layer 63 n-GaInP (As) lower clad layer 64 GaAs optical guide layer _{65a, 65b Ga 0.6 In 0.4 N} 0.005 As 0.995 quantum well layer 66 GaAs barrier layer 67 active layer (light emitting layer)
68 GaAs light guide layer 69 p-GaInP (As) upper cladding layer 70 p-GaAs contact layer 72 p-side electrode 71 insulating film 73 n-side electrode 81 n-GaAs substrate 82 n-GaAs buffer layer 83 n-GaInP (As) Lower cladding layer 84 GaAs optical guide layer 85a, 85b Ga _0.65 In _0.35 N _0.007 As _0.993 Quantum well layer 86a, 86b, 86c GaAs barrier layer 87 Active layer (light emitting layer)
88 GaAs light guide layer 89 p-GaInP (As) upper cladding layer 90 p-GaAs contact layer 92 p-side electrode 91 insulating film 93 n-side electrode 101 GaAs substrate 102 lower semiconductor multilayer reflector 103 GaAs spacer layer 104 active Layer 105 GaAs spacer layer 106 current constriction layer 107 current injection layer 108 p-GaAs contact layer 109 upper semiconductor multilayer reflector 110 insulating film 111 p-side electrode 112 n-side electrode 121 GaAs substrate 122 GaInPAs cladding layer 123 active layer 124 GaInPAs cladding layer 125 Current constriction layer 126 Current injection portion 127 p-GaAs contact layer 128 Upper semiconductor multilayer mirror 129 Lower dielectric multilayer reflector 130 Insulating film 131 p-side electrode 132 n-side electrode 131 p-side electrode 1 32 n-side electrode

Claims (5)

An active layer including a strained quantum well layer and a cladding layer for confining light and carriers are formed on a semiconductor substrate. In a semiconductor light emitting device having an oscillation wavelength of 1.3 μm, the strained quantum well layer contains In and N. In addition, the N composition in the group V element is 0 to 1%, the In composition in the group III element is in a range larger than 30%, and the strain amount of the strain quantum well layer with respect to the semiconductor substrate and the cladding layer is 2%. A semiconductor light emitting element characterized by having a strain amount exceeding. An active layer including a strained quantum well layer and a cladding layer for confining light and carriers are formed on a semiconductor substrate, and the strained quantum well for the semiconductor substrate and the cladding layer in a semiconductor light emitting device having an oscillation wavelength of 1.3 μm band. A semiconductor light emitting element characterized in that the strain amount of the layer exceeds 2%, and the plane orientation of the semiconductor substrate is within a range of an inclination angle of (5) from (100). 3. The semiconductor light emitting device according to claim 1, wherein GaInP or GaInPAs is used as the cladding layer. 3. The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device is a surface light emitting type. 3. The semiconductor light emitting element according to claim 1, wherein a barrier layer for compensating stress is formed in the active layer in the vicinity of the strained quantum well layer.

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