JP2006120884A - Semiconductor light emitting device, surface-emission laser, surface-emission laser array, image forming apparatus, optical pickup system, optical transmission module, optical transceiving module, and optical communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor light emitting device which is equipped with a quantum well active layer where carriers are sufficiently trapped; and which has a high gain, excellent temperature characteristics, a low threshold value, a high output power, and excellent reliability. <P>SOLUTION: A lower clad layer, a lower optical guide layer, an active layer, an upper optical guide layer, and an upper clad layer are formed on a GaAs substrate for the formation of the semiconductor light emitting device. The above active layer is equipped with a Ga<SB>c</SB>In<SB>1-c</SB>P<SB>d</SB>As<SB>1-d</SB>(0<c<1, 0≤d≤1) compressive strain quantum well active layer and a Ga<SB>e</SB>In<SB>1-e</SB>P<SB>f</SB>As<SB>1-f</SB>(0<e<1, 0≤f≤1) tensile strain barrier layer, an (Al<SB>a</SB>Ga<SB>1-a</SB>)<SB>b</SB>In<SB>1-b</SB>P (0<a≤1, 0<b<1) layer having a larger band gap energy than the active layer is used as, at least, a part of either of the lower clad layer and the upper clad layer, and the absolute value of the strain volume of the barrier layer is set larger than that of the quantum well active layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a semiconductor light emitting element, a surface emitting laser, a surface emitting laser array, an image forming apparatus, an optical pickup system, an optical transmission module, an optical transmission / reception module, and an optical communication system.

  AlGaAs-based semiconductor lasers are used in consumer applications such as light sources for optical pickups such as CDs and light sources for image forming apparatuses such as printers, as semiconductor lasers having a wavelength shorter than 850 nm. For example, Al is added to the quantum well active layer of a semiconductor laser of 780 nm band by about 12% by composition ratio. AlGaAs having a large Al composition is used for other constituent layers such as a barrier layer, a light guide layer (a spacer layer in a surface emitting laser), and a cladding layer (sometimes called a spacer layer in a surface emitting laser). . However, in an AlGaAs semiconductor laser having a wavelength band shorter than 850 nm, the active layer becomes a wide gap as the wavelength becomes shorter, so that the band discontinuity with the barrier layer, the light guide layer, and the cladding layer (spacer layer) is small. As a result, carrier confinement in the active layer is weakened, and there is a problem that it is difficult to obtain good characteristics particularly in temperature characteristics as compared with a semiconductor laser of 850 nm band. The surface emitting laser is more problematic because the carrier density is high. Therefore, in a semiconductor light emitting device having a wavelength of about 630 nm to 700 nm, an AlGaInP-based material having the widest gap among III-V group materials other than a GaN-based material is used.

  Note that an edge-emitting semiconductor laser is mainly used for a semiconductor light emitting device having a wavelength shorter than 850 nm. In contrast, surface-emitting semiconductor lasers (surface-emitting lasers) are semiconductor lasers that emit light in a direction perpendicular to the substrate, and can achieve high performance at a lower cost than the edge-emitting type, and are integrated. Has attracted attention in recent years. Conventionally, surface emitting lasers in the 850 nm band and 980 nm band have good carrier confinement in the active layer. Specifically, in the surface emitting laser of 850 nm band, GaAs is used for the quantum well active layer, and AlGaAs is used for the barrier layer and the spacer layer (cladding layer). Further, a high-performance AlGaAs-based reflector (DBR) and a current confinement structure using an Al oxide film can be adopted, thereby realizing a practical level of performance. However, since the surface emitting laser requires a high carrier density, it is difficult to improve the performance of the surface emitting laser having a wavelength shorter than 850 nm as compared with the edge emitting laser.

  Also, in recent years, a strain compensation structure comprising a structure in which the quantum well active layer has a compressive strain composition and the barrier layer has a tensile strain composition, or a strain compensation structure having a structure in which the quantum well active layer has a tensile strain composition and the barrier layer has a compressive strain composition. It is often used as an active layer of semiconductor light emitting devices such as lasers.

  When the strain of the quantum well active layer increases, the band separation between the heavy hole and the light hole increases, so that the gain increases and the operation with low threshold current and high luminous efficiency becomes possible. In order to obtain a large gain increase by increasing the strain amount of the quantum well active layer as much as possible, the strain on the opposite side is applied to the barrier layer to reduce the strain amount of the entire active layer. For this reason, conventionally, the strain amount of the quantum well active layer is larger than that of the barrier layer. However, since the AlGaAs-based material is composed of a lattice matching system, the above-described strain effect cannot be used.

  Therefore, Patent Document 1 proposes a surface-emitting laser with a wavelength of 850 nm that employs an InGaAlAs quantum well active layer having a compressive strain of 1% and an AlGaAsP barrier layer having a 0.7% tensile strain. Document 1 shows that the strain thickness can increase the critical thickness of the quantum well active layer and increase the number of well layers, and the effect of the strain active layer can increase the output.

  However, since active Al is added to the active layer of InGaAlAs and AlGaAs lasers, oxygen is taken in during the growth and processing in the configuration of Patent Document 1, and a non-radiative recombination center is formed. There has been a problem that the luminous efficiency and reliability are lowered.

  In order to avoid this problem, there is an example using a strained quantum well active layer using an Al-free GaInPAs-based material as an active layer. Patent Document 2 discloses a surface emission that employs an Al-free active region (a quantum well active layer and a layer adjacent thereto) for the purpose of suppressing the formation of a non-radiative recombination center with a surface emitting laser having a wavelength band shorter than 850 nm. Lasers (780 nm band) have been proposed. In this surface emitting laser, GaAsP having tensile strain is used in the quantum well active layer in order to employ an Al-free active region, and in order not to generate misfit dislocations in the barrier layer, the amount of strain in the active layer GaInP having a compressive strain that is equal and opposite strain is used, and lattice-matched GaInP is used for the spacer layer (the layer between the cladding layer and the first and third quantum well active layers), and AlGaInP is used for the cladding layer. According to Patent Document 2, since the active region is Al-free, the reliability is improved.

  Further, Non-Patent Document 1 discloses GaInPAs (+ 0.6%) having a compressive strain in the quantum well active layer in order to increase the gain of the active layer in addition to the effect of the active region being Al-free. GaInP having lattice matching or tensile strain (−0.3%) is used for the barrier layer, and lattice matching AlGaInP is used for the spacer layer (the layer between the cladding layer and the first and third quantum well active layers). And a 780 nm band surface emitting laser in which AlGaInP (Al composition is larger than that of the spacer layer) is used for the cladding layer. In this surface emitting laser of Non-Patent Document 1, the GaInP barrier layer has lattice matching or tensile strain and has a larger band gap than the compressive strain composition, so that carrier confinement is better than the structure of Patent Document 1 described above. ing. Further, AlGaInP having a wider gap than AlGaAs is used for the clad layer, and the effect of confining carriers overflowing from the barrier layer is high, and the gain is further increased, so that a low threshold value operation is possible.

  Non-Patent Document 2 uses an InGaAsP quantum well active layer having a compressive strain of 1.6%, and the strain amount of an InGaP barrier layer having a tensile strain is 0.0%, 0.5%, and 0.75. % And 1.0%, and the results of characteristic evaluation are shown. The characteristic evaluation in Non-Patent Document 2 was performed with an edge-emitting laser having an oscillation wavelength of 730 nm. According to this, the threshold value decreases when the tensile strain amount is about 0.5% to 0.75%, and the internal quantum efficiency and the characteristic temperature are improved. This is because the effect of strain compensation and the band gap of the barrier layer become larger and carrier confinement becomes better. However, when the strain becomes higher by 1%, the characteristic temperature is further improved, but the threshold value is increased. It has been reported that the internal quantum efficiency decreases.

  Further, Patent Document 3 shows an example in which a compressive strain GaInPAs quantum well active layer has a strain amount of 1% or less, a P composition of 0.55 or more, and a barrier layer having a large tensile strain. Note that AlGaAs is used for the cladding layer and the light guide layer. According to Patent Document 3, when the strain amount of the barrier layer is increased, the band discontinuity with the quantum well active layer is increased, the carrier overflow can be reduced, and the threshold current can be reduced.

However, the conventional semiconductor light emitting device having an Al-free active layer with a wavelength shorter than 850 nm on the GaAs substrate has insufficient carrier confinement, and the semiconductor light emitting devices in the 850 nm band and the 980 nm band in terms of light output and temperature characteristics. It was greatly inferior to. In particular, surface-emitting lasers that require a high carrier density have not obtained good characteristics.
JP-A-9-162482 JP-A-9-107153 JP 2003-152281 A IEEE Photonics Technology Letters, Vol. 12, no. 6, 2000 (Wisconsin Univ.) IEEE Journal of Selected Topics in Quantum Electronics, Vol. 5, no. 3, 1999 (Wisconsin Univ.)

  The present invention provides a semiconductor light-emitting device in which carrier confinement in a quantum well active layer is sufficiently performed, gain is large, temperature characteristics are good, low threshold value, high output, and excellent reliability are provided. It is an object of the present invention to provide a surface emitting laser, a surface emitting laser array, an image forming apparatus, an optical pickup system, an optical transmission module, an optical transmission / reception module, and an optical communication system.

In order to achieve the above object, according to the first aspect of the present invention, a lower cladding layer, a lower light guide layer, an active layer, an upper light guide layer, and an upper cladding layer are formed on a GaAs substrate. In the semiconductor light emitting device, the active layer includes Ga _c In _1-c P _d As _1-d (0 <c <1, 0 ≦ d ≦ 1) compressive strain quantum well active layer, Ga _e In _1-e P _f As _1-f (0 <e ≦ 1, 0 ≦ f ≦ 1) a tensile strain barrier layer, and at least part of at least one of the lower clad layer and the upper clad layer has active (Al _a Ga _1-a ) _b In _1-b P (0 <a ≦ 1, 0 <b <1) layer having _a larger band gap energy than the layer is used, and the absolute amount of strain of the barrier layer The value is larger than the absolute value of the strain amount of the quantum well active layer. That.

  According to a second aspect of the present invention, in the semiconductor light emitting device according to the first aspect, the semiconductor light emitting device has an oscillation wavelength longer than about 680 nm.

  According to a third aspect of the present invention, in the semiconductor light emitting device according to the first or second aspect, the plane orientation of the GaAs substrate is inclined at an angle in the range of 5 ° to 20 ° in the (111) A plane direction. It is characterized by the (100) plane.

According to a fourth aspect of the present invention, there is provided an active layer having at least one quantum well active layer and a barrier layer for generating laser light on a GaAs substrate, and at least one kind provided above and below the active layer. In a surface emitting laser including a resonator region including an upper spacer layer and a lower spacer layer made of the above materials, and an upper reflector and a lower reflector provided above and below the resonator region, the upper reflector and the lower reflector comprises a semiconductor distributed Bragg reflector in which the refractive index is reflected by periodically changed optical interference of incident light, at least a portion of a semiconductor distributed Bragg _{reflector, Al x Ga 1-x as} (0 <x ≦ 1) and the layer refractive index is small _{consisting, Al y Ga 1-y as} (0 ≦ y <x ≦ 1) consisting of a refractive index consists of a large consisting layer, an upper spacer layer and the lower space At least a portion of at least one of the spacer layer among the _{layers, (Al a Ga 1-a} ) b In 1-b P (0 <a ≦ 1,0 <b <1) is used, the quantum well active The layer is composed of Ga _c In _1-c P _d As _1-d (0 <c <1, 0 ≦ d ≦ 1) having compressive strain, and the barrier layer is Ga _e In _1-e P _f As having tensile strain. _1−f (0 <e ≦ 1, 0 ≦ f ≦ 1), and the absolute value of the strain amount of the barrier layer is larger than the absolute value of the strain amount of the quantum well active layer.

  The invention according to claim 5 is the surface emitting laser according to claim 4, wherein the surface emitting laser has an oscillation wavelength longer than about 680 nm.

  According to a sixth aspect of the present invention, in the surface emitting laser according to the fourth or fifth aspect, the surface orientation of the GaAs substrate is inclined at an angle in the range of 5 ° to 20 ° in the (111) A plane direction. It is characterized by the (100) plane.

  According to a seventh aspect of the present invention, in the surface emitting laser according to the sixth aspect, the outer peripheral shape of the active layer viewed from the light emitting direction has an anisotropy that is long in the (111) A plane direction. It is characterized by having.

  According to an eighth aspect of the invention, there is provided a surface emitting laser comprising a plurality of the surface emitting lasers according to any one of the fourth to seventh aspects formed on the same substrate. It is an array.

  In the invention described in claim 9, the surface emitting laser according to any one of claims 4 to 7 or the surface emitting laser array according to claim 8 is used as a writing light source. An image forming apparatus characterized by the above.

  The invention described in claim 10 is characterized in that the surface emitting laser according to any one of claims 4 to 7 or the surface emitting laser array according to claim 8 is used as a light source. An optical pickup system is characterized.

  The invention described in claim 11 is characterized in that the surface emitting laser according to any one of claims 4 to 7 or the surface emitting laser array according to claim 8 is used as a light source. An optical transmission module is characterized.

  The invention described in claim 12 is characterized in that the surface emitting laser according to any one of claims 4 to 7 or the surface emitting laser array according to claim 8 is used as a light source. This is a featured optical transceiver module.

  The invention according to claim 13 is characterized in that the surface emitting laser according to any one of claims 4 to 7 or the surface emitting laser array according to claim 8 is used as a light source. An optical communication system is characterized.

According to the first to third aspects of the present invention, semiconductor light emission in which a lower cladding layer, a lower light guide layer, an active layer, an upper light guide layer, and an upper cladding layer are formed on a GaAs substrate. In the device, the active layer includes Ga _c In _1-c P _d As _1-d (0 <c <1, 0 ≦ d ≦ 1) compressive strain quantum well active layer, Ga _e In _1-e P _f As _1-f (0 <e ≦ 1, 0 ≦ f ≦ 1) a tensile strain barrier layer, and at least part of at least one of the lower cladding layer and the upper cladding layer is formed by an active layer (Al _a Ga _1-a ) _b In _1-b P (0 <a ≦ 1, 0 <b <1) layer is used, and the absolute value of the strain amount of the barrier layer is Since it is larger than the absolute value of the strain amount of the quantum well active layer, Yaria confinement is sufficiently performed, the gain is large, the temperature characteristic is a good, low threshold, high-power, even it is possible to provide a semiconductor light-emitting device having excellent reliability.

According to the inventions of claims 4 to 7, an active layer having at least one quantum well active layer for generating laser light and a barrier layer on the GaAs substrate, and upper and lower portions of the active layer A surface emitting device comprising: a resonator region including an upper spacer layer and a lower spacer layer made of at least one material; and an upper reflector and a lower reflector provided above and below the resonator region. In the laser, the upper reflecting mirror and the lower reflecting mirror include a semiconductor distributed Bragg reflector that periodically changes the refractive index and reflects incident light by light wave interference, and at least a part of the semiconductor distributed Bragg reflector includes Al _x Ga. _A layer having a small refractive index composed of _1-x As (0 <x ≦ 1) and a layer having a large refractive index composed of Al _y Ga _1-y As (0 ≦ y <x ≦ 1). Special At least in part on the at least one spacer layer of the support layer and the lower spacer _layer, the _{(Al a Ga 1-a)} b In 1-b P (0 <a ≦ 1,0 <b <1) using The quantum well active layer is made of Ga _c In _1-c P _d As _1-d (0 <c <1, 0 ≦ d ≦ 1) having compressive strain, and the barrier layer is Ga _e In ₁ having tensile strain. consists _{-e P f As 1-f (} 0 <e ≦ 1,0 ≦ f ≦ 1), the absolute value of the strain in the barrier layer is greater than the absolute value of the strain in the quantum well active layer, a quantum well It is possible to provide a surface emitting laser in which carriers are sufficiently confined in the active layer, gain is large, temperature characteristics are good, a low threshold value, high output, and excellent reliability are provided.

  According to an eighth aspect of the invention, there is provided a surface comprising a plurality of surface emitting lasers according to any one of the fourth to seventh aspects formed on the same substrate. Since it is a light emitting laser array, it is possible to provide a surface emitting laser array having a large gain, good temperature characteristics, a low threshold value, a high output, and excellent reliability.

  According to the invention described in claim 9, the surface emitting laser according to any one of claims 4 to 7 or the surface emitting laser array according to claim 8 is used as a writing light source. Therefore, it is possible to provide an image forming apparatus that can perform high-speed printing and reduce costs.

  According to the invention described in claim 10, the surface emitting laser according to any one of claims 4 to 7 or the surface emitting laser array according to claim 8 is used as a light source. Therefore, it is possible to realize a handy type optical pickup system with high reliability and long-lasting power.

  According to the eleventh aspect of the present invention, the surface emitting laser according to any one of the fourth to seventh aspects or the surface emitting laser array according to the eighth aspect is used as a light source. Therefore, an economical and high-speed optical transmission module can be realized.

  According to the invention described in claim 12, the surface emitting laser according to any one of claims 4 to 7 or the surface emitting laser array according to claim 8 is used as a light source. Therefore, an economical and high-speed optical transceiver module can be realized.

According to the invention described in claim 13, the surface emitting laser according to any one of claims 4 to 7 or the surface emitting laser array according to claim 8 is used as a light source. Therefore, an economical optical communication system can be realized.

  Hereinafter, the best mode for carrying out the present invention will be described.

(First form)
According to a first aspect of the present invention, there is provided a semiconductor light emitting device in which a lower cladding layer, a lower light guide layer, an active layer, an upper light guide layer, and an upper cladding layer are formed on a GaAs substrate. The layers are Ga _c In _1-c P _d As _1-d (0 <c <1, 0 ≦ d ≦ 1) compression strain quantum well active layer, Ga _e In _1-e P _f As _1-f (0 <E ≦ 1, 0 ≦ f ≦ 1) a tensile strain barrier layer, and at least part of at least one of the lower cladding layer and the upper cladding layer has a band gap energy higher than that of the active layer. A large (Al _a Ga _1-a ) _b In _1-b P (0 <a ≦ 1, 0 <b <1) layer is used, and the absolute value of the strain amount of the barrier layer is that of the quantum well active layer. It is characterized by being larger than the absolute value of the amount of distortion.

According to the first aspect of the present invention, in a semiconductor light emitting device in which a lower cladding layer, a lower light guide layer, an active layer, an upper light guide layer, and an upper cladding layer are formed on a GaAs substrate, The active layer includes Ga _c In _1-c P _d As _1-d (0 <c <1, 0 ≦ d ≦ 1) compressive strain quantum well active layer, Ga _e In _1-e P _f As _1-f (0 <e ≦ 1, 0 ≦ f ≦ 1) having a tensile strain barrier layer, and at least part of at least one of the lower cladding layer and the upper cladding layer has a band gap more than the active layer. A high energy (Al _a Ga _1-a ) _b In _1-b P (0 <a ≦ 1, 0 <b <1) layer is used, and the absolute value of the strain amount of the barrier layer is the quantum well activity. Since the absolute value of the strain amount of the layer is larger, carrier closure to the quantum well active layer Because is sufficiently performed, the gain is large, the temperature characteristic is a good, low threshold, high-power, even it is possible to provide a semiconductor light-emitting device having excellent reliability.

  That is, in order to sufficiently confine carriers, it is necessary to increase both the band discontinuity between the quantum well active layer and the barrier layer and the band discontinuity between the quantum well active layer and the cladding layer (spacer layer in the surface emitting laser). There is. This is because carriers overflowing the barrier layer are finally blocked by the band discontinuity with the cladding layer, so it is necessary to increase the band discontinuity between the quantum well active layer and the cladding layer. This is because, in order to reduce non-radiative recombination due to, it is preferable in terms of light emission efficiency to block the carrier with a barrier layer as much as possible. That is, either one is insufficient.

In the first embodiment of the present invention, an AlGaInP material, that is, (Al _a Ga _1-a ) _b In _1-b P (0 <a ≦ 1, 0 <b <1) is used for at least a part of the cladding layer. As a result, the band gap difference between the cladding layer and the quantum well active layer can be made extremely large compared to the case where the cladding layer is formed of AlGaAs, and carrier confinement is improved. Preferred compositions a and b of (Al _a Ga _1-a ) _b In _1-b P (0 <a ≦ 1, 0 <b <1) have the largest band gap in the typical composition range of the AlGaAs cladding layer. The band gap is larger than that of the large Al _x Ga _1-x As (x = 0.6, Eg = 2.0226 eV), 0.2 ≦ a (b is about 0.5, which is a composition that lattice matches with the GaAs substrate). preferable. More preferably, about 0.5 ≦ a ≦ 0.7.

In the first embodiment of the present invention, the active layer includes Ga _c In _1-c P _d As _1-d (0 <c <1, 0 ≦ d ≦ 1) compression strain quantum well active layer, Ga _e In _1-e P _f As _1-f (0 <e ≦ 1, 0 ≦ f ≦ 1) tensile strained barrier layer, and the absolute value of the strain amount of the barrier layer is the absolute value of the strain amount of the quantum well active layer By making it larger, the band gap difference between the barrier layer and the quantum well active layer can be made extremely large, and carrier confinement is improved.

  In general, a group III-V semiconductor material using the same constituent elements has a composition that can increase the band gap as the lattice constant decreases, and the greater the amount of tensile strain of the barrier layer, the higher the carrier confinement in the quantum well active layer. Can be improved. In other words, if the tensile strain amount of the barrier layer is larger than the compressive strain amount of the quantum well active layer, a material having a large band gap can be used as the barrier layer, and carrier confinement is improved, so that the gain of the active layer is high. Thus, it is possible to obtain a semiconductor light emitting device having excellent temperature characteristics, a low threshold value, and a high output.

  However, the quantum well active layer and the barrier layer have opposite strains. The interface is strained by adding the amount of tensile strain and the amount of compressive strain, and the value is limited. This value depends on conditions such as the growth temperature. If the compressive strain amount of the quantum well active layer is increased, the tensile strain amount of the barrier layer cannot be increased. On the other hand, when the tensile strain amount of the barrier layer is larger than the compressive strain amount of the quantum well active layer, a material having a large band gap can be used as the barrier layer.

  Thereby, both the band discontinuity between the quantum well active layer and the barrier layer and the band discontinuity between the quantum well active layer and the cladding layer can be increased, and carrier confinement can be sufficiently performed.

  The effect of making the strain amount of the tensile strain barrier layer larger than the strain amount of the quantum well active layer can be obtained as follows. That is, when a GaAs substrate is used, GaAsP, AlGaAsP, GaInP, AlInP, GaInPAs, AlGaInP, and AlGaInPAs are materials having a composition that can increase the band gap as the lattice constant is reduced. The above effects can be obtained. When an InP substrate is used, GaInP, GaInAs, AlInAs, AlGaInAs, GaInPAs, AlGaInP, and AlGaInPAs are materials that have a composition that can increase the band gap as the lattice constant is reduced. The above effects can be obtained.

  In particular, when GaInPAs, which is a highly immiscible material, is used as the quantum well active layer, the higher the amount of strain, the more difficult it becomes to produce a homogeneous composition mixed crystal, which makes it difficult to obtain a high-quality crystal. There is a limit to gain improvement. However, since the barrier layer is made of a wide gap material, carrier confinement is improved, so that the gain of the active layer is increased without increasing the strain of the quantum well active layer, and the quantum well active layer is improved in quality. It becomes easy to produce. Accordingly, it is possible to obtain a semiconductor light emitting device having excellent temperature characteristics, a low threshold value, and a high output. Since the widest gap is GaInP among GaInPAs materials having the same lattice constant (strain), it is preferable to use GaInP for the barrier layer.

  In addition, according to the Al-free active layer composed of the GaInPAs quantum well active layer and the GaInPAs barrier layer, in the case of the edge-emitting laser, the output can be increased by increasing the COD level. In addition, since the active layer does not contain Al that easily takes in oxygen, the reliability can be improved. According to claim 1, since a wide gap barrier layer can be adopted as compared with the conventional one while maintaining Al free, carrier confinement is improved, so that the gain of the active layer can be increased without increasing the strain of the quantum well active layer. In addition, the quantum well active layer can be easily manufactured with high quality. As a result, a semiconductor light emitting device having excellent temperature characteristics, low threshold, high output and excellent reliability can be obtained. Although the wavelength ranges from red to near infrared, the effect is large in a semiconductor light emitting device having a wavelength shorter than 850 nm, particularly a semiconductor laser, due to the limitation of the band gap of the barrier layer of the conventional semiconductor light emitting device. Of course, the above effect can be obtained even at a wavelength longer than 850 nm.

  Note that when an As-based material such as AlGaAs is formed on top of a P-based material such as AlGaInP or GaInPAs, P on the P-based material is replaced with As, and an As-rich material with a narrow band gap tends to be formed. Further, at the interface, In separation, such as In carry over to the AlGaAs layer, occurs. If this portion is between the active layer and the clad layer, there is a problem of absorption of light generated in the active layer, leading to an increase in threshold value. Therefore, it is better not to insert an As-based material such as AlGaAs between the GaInPAs-based active layer and the upper AlGaInP cladding layer. For the light guide layer between the GaInPAs-based active layer and the AlGaInP cladding layer, it is desirable to use AlGaInP having a narrower Al composition than the cladding layer and having a narrow gap.

(Second form)
According to a second aspect of the present invention, in the semiconductor light emitting device of the first aspect, the semiconductor light emitting device has an oscillation wavelength longer than about 680 nm.

  In the present invention, by using an AlGaInP-based cladding layer and a wide gap barrier layer, if the composition wavelength is longer than 680 nm, even if an Al-free active layer (quantum well active layer and barrier layer) is used, Carrier confinement equivalent to or higher than that in the case of a 780 nm band semiconductor light-emitting device using an AlGaAs-based active layer is possible, and the effect of a strained quantum well active layer is also added. It is possible to obtain characteristics equivalent to or better than the case.

(Third form)
According to a third aspect of the present invention, in the semiconductor light emitting device of the first or second aspect, the plane orientation of the GaAs substrate is inclined at an angle in the range of 5 ° to 20 ° in the (111) A plane direction (100 ) Surface.

  In crystal growth of P-based materials such as AlGaInP and GaInP, a (100) GaAs substrate whose plane orientation is inclined at an angle in the range of 5 ° to 20 ° with respect to the (111) A plane direction is taken into consideration. This reduces the adverse effects on device characteristics such as semiconductor lasers, such as the reduction of the band gap due to the formation of natural superlattices, the deterioration of surface properties due to the generation of hillocks (hill-like defects), and the generation of non-radiative recombination centers. be able to. Note that crystal growth becomes more difficult as the inclination becomes larger, such as (311) A. On the other hand, crystal growth can be easily performed by using a (100) GaAs substrate whose plane orientation is inclined at an angle in the range of 5 ° to 20 ° in the (111) A plane direction.

(4th form)
According to a fourth aspect of the present invention, there is provided an active layer having at least one quantum well active layer and a barrier layer for generating laser light on a GaAs substrate, and at least one kind of an active layer provided above and below the active layer. A surface emitting laser comprising: a resonator region including an upper spacer layer and a lower spacer layer made of a material; and an upper reflector and a lower reflector provided above and below the resonator region. lower reflecting mirror includes a semiconductor distributed Bragg reflector in which the refractive index is reflected by periodically changed optical interference of incident light, at least a portion of a semiconductor distributed Bragg _{reflector, Al x Ga 1-x as} (0 < a layer refractive index is small consisting _{x ≦ 1), Al y Ga} 1-y as (0 ≦ y <x ≦ 1) consisting of a refractive index consists of a large consisting layer, the upper spacer layer and the lower spacer layer At least a portion of Chino at least one of the spacer _{layer, (Al a Ga 1-a} ) b In 1-b P (0 <a ≦ 1,0 <b <1) is used, the quantum well active layer is compressed The strained Ga _c In _1-c P _d As _1-d (0 <c <1, 0 ≦ d ≦ 1), and the barrier layer has tensile strain, Ga _e In _1-e P _f As _1-f (0 <e ≦ 1, 0 ≦ f ≦ 1), and the absolute value of the strain amount of the barrier layer is larger than the absolute value of the strain amount of the quantum well active layer.

According to the fourth aspect of the present invention, an active layer having at least one quantum well active layer for generating laser light and a barrier layer on a GaAs substrate, and at least one provided above and below the active layer. In a surface emitting laser including a resonator region including an upper spacer layer and a lower spacer layer made of various materials, and an upper reflector and a lower reflector provided above and below the resonator region, the upper reflection The mirror and the lower reflecting mirror include a semiconductor distributed Bragg reflector that periodically changes the refractive index and reflects incident light by light wave interference, and at least a part of the semiconductor distributed Bragg reflector includes Al _x Ga _1-x As ( 0 <x ≦ 1) and the layer refractive index is small _{consisting, Al y Ga 1-y as} (0 ≦ y <x ≦ 1) consisting of a refractive index consists of a large consisting layer, an upper spacer layer and the lower space At least a portion of at least one of the spacer layer among the _{layers, (Al a Ga 1-a} ) b In 1-b P (0 <a ≦ 1,0 <b <1) is used, the quantum well active The layer is composed of Ga _c In _1-c P _d As _1-d (0 <c <1, 0 ≦ d ≦ 1) having compressive strain, and the barrier layer is Ga _e In _1-e P _f As having tensile strain. _1−f (0 <e ≦ 1, 0 ≦ f ≦ 1), and since the absolute value of the strain amount of the barrier layer is larger than the absolute value of the strain amount of the quantum well active layer, carriers to the quantum well active layer It is possible to provide a surface emitting laser which is sufficiently confined, has a large gain, has a good temperature characteristic, has a low threshold value, a high output, and is excellent in reliability.

That is, in the surface emitting laser according to the fourth aspect of the present invention, an AlGaInP material, that is, (Al _a Ga _1-a ) _b In _1-b P (0 <a ≦ 1, 0 < _b ) is formed on at least a part of the spacer layer. By using <1), the band gap difference between the spacer layer and the quantum well active layer can be made extremely large as compared with the case where the spacer layer is formed of AlGaAs, and carrier confinement is improved. In addition, by setting the quantum well active layer to a compressive strain composition, it is possible to reduce the threshold and increase the efficiency (high output) by the band separation effect of the valence band. Furthermore, since the tensile strain amount of the barrier layer is larger than the compressive strain amount of the quantum well active layer, a material having a large band gap can be used as the barrier layer, carrier confinement by the barrier layer is improved, and the quantum well active layer Can be easily produced with high quality. By reducing the threshold value by increasing the gain and quality, it is possible to reduce the reflectivity of the DBR (distributed Bragg reflector) on the light extraction side, and further increase the output.

Further, the barrier layer and the quantum well active layer have been used GaInPAs material _{(i.e., Ga c In 1-c P} d As 1-d (0 is a quantum well active layer having a compressive strain <c <1, 0 ≦ d ≦ 1), and the barrier layer is made of Ga _e In _1-e P _f As _1-f (0 <e ≦ 1, 0 ≦ f ≦ 1) having tensile strain, and is made of a material not containing Al. Active layer is configured), and since it is an Al-free active region (quantum well active layer and a layer adjacent thereto), the incorporation of oxygen can be reduced and the formation of non-radiative recombination centers can be suppressed, A long-life surface emitting laser can be realized. Due to the limitation of the band gap of the barrier layer of the conventional surface emitting laser, the effect is large in the surface emitting laser having a wavelength shorter than 850 nm.

  Note that when an As-based material such as AlGaAs is formed on top of a P-based material such as AlGaInP or GaInPAs, P on the P-based material is replaced with As, and an As-rich material with a narrow band gap tends to be formed. Further, at the interface, In separation, such as In carry over to the AlGaAs layer, occurs. If this portion is close to the active layer, there will be a problem of absorption of light generated in the active layer, leading to an increase in threshold value. Therefore, it is better not to insert an As-based material such as AlGaAs between the GaInPAs-based active layer and the upper AlGaInP spacer layer. An As-based material such as AlGaAs may be provided on the side opposite to the active layer of the wide gap AlGaInP spacer layer. When a semiconductor layer is provided between the GaInPAs-based active layer and the AlGaInP spacer layer, it is desirable to use AlGaInP having a narrower Al composition and a narrow gap than the AlGaInP spacer layer.

(5th form)
According to a fifth aspect of the present invention, in the surface emitting laser according to the fourth aspect, the surface emitting laser has an oscillation wavelength longer than about 680 nm.

  In the present invention, by using an AlGaInP-based spacer layer and a wide gap barrier layer, if the composition wavelength is longer than 680 nm, even if an Al-free active layer (quantum well active layer and barrier layer) is used, Carrier confinement equivalent to or higher than that in the case of a surface emitting laser of 780 nm band by an AlGaAs-based active layer is possible and the effect of a strained quantum well active layer is also added. It is possible to obtain characteristics equivalent to or better than the case.

(Sixth form)
According to a sixth aspect of the present invention, in the surface emitting laser according to the fourth or fifth aspect, the plane orientation of the GaAs substrate is inclined at an angle in the range of 5 ° to 20 ° in the (111) A plane direction (100 ) Surface.

  In crystal growth of P-based materials such as AlGaInP and GaInP, a (100) GaAs substrate whose plane orientation is inclined at an angle in the range of 5 ° to 20 ° with respect to the (111) A plane direction is taken into consideration. This reduces the adverse effects on the device characteristics of surface emitting lasers, such as the reduction of the band gap due to the formation of natural superlattices, the deterioration of surface properties due to the generation of hillocks (hill-like defects) and the occurrence of non-radiative recombination centers. be able to. Note that crystal growth becomes more difficult as the inclination becomes larger, such as (311) A. On the other hand, crystal growth can be easily performed by using a (100) GaAs substrate whose plane orientation is inclined at an angle in the range of 5 ° to 20 ° in the (111) A plane direction. Further, in the surface emitting laser of the sixth embodiment, the effect of optical gain anisotropy is increased by the compression strain quantum well active layer, and polarization control becomes possible.

(7th form)
According to a seventh aspect of the present invention, in the surface emitting laser according to the sixth aspect, the outer peripheral shape of the active layer viewed from the light emitting direction has an anisotropy that is long in the (111) A plane direction. It is characterized by being.

  Since the (100) GaAs substrate whose plane orientation is inclined at an angle in the range of 5 ° to 20 ° with respect to the (111) A plane direction is used, polarization control is currently regarded as the most promising (311) B The effect of using the substrate (25 ° tilt) cannot be used, and the optical gain anisotropy due to the use of the tilted substrate is reduced. However, in the present invention, this decrease is applied to the quantum well active layer by compressive strain. By increasing the optical gain anisotropy due to the illuminating effect, and providing the anisotropy to the outer peripheral shape of the active layer as viewed from the light emitting direction of the surface emitting laser, and making it long in the (111) A plane direction By compensating for the increase in optical gain in the substrate tilt direction ((111) A plane direction), the polarization direction can be controlled. The outer peripheral shape of the active layer is the shape of the oscillating region and the shape of the active layer region into which current is injected. When current confinement is performed, it may be considered as a shape of current confinement.

  As described above, according to the seventh embodiment of the present invention, the gain of the active layer is large, the threshold is low, the output is excellent, and the polarization direction is controlled. Thus, a surface emitting laser having a wavelength shorter than 850 nm can be provided.

(Eighth form)
According to an eighth aspect of the present invention, there is provided a surface-emitting laser array comprising a plurality of surface-emitting lasers according to any one of the fourth to seventh aspects formed on the same substrate.

  According to an eighth aspect of the present invention, there is provided a surface emitting laser array comprising a plurality of surface emitting lasers according to any one of the fourth to seventh aspects formed on the same substrate. Therefore, it is possible to provide a surface emitting laser array with sufficient carrier confinement in the quantum well active layer, large gain, good temperature characteristics, low threshold, high output, and excellent reliability. can do.

  That is, since the surface emitting laser is a surface emitting type, it can be easily arrayed and is formed by a normal semiconductor process, so that the element position system is high. In addition, by integrating a large number of surface-emitting lasers capable of high-power operation on the same substrate, when applied to a writing optical system, simultaneous multi-beam writing is facilitated, and the writing speed is greatly improved. Even if the dot density increases, printing can be performed without reducing the printing speed. Further, when the writing dot density is the same, the printing speed can be increased. In addition, when applied to communication, data transmission by multiple beams can be performed at the same time, so high-speed communication can be performed. Further, the surface emitting laser operates with low power consumption, and particularly when incorporated in a device, the temperature rise can be reduced.

(9th form)
According to a ninth aspect of the present invention, there is provided an image in which the surface emitting laser according to any one of the fourth to seventh aspects or the surface emitting laser array according to the eighth aspect is used as a writing light source. A forming apparatus (for example, a printer or a facsimile machine).

  According to a ninth aspect of the present invention, the surface-emitting laser according to any one of the fourth to seventh aspects or the surface-emitting laser array according to the eighth aspect is used as a writing light source. Therefore, it is possible to provide an image forming apparatus that can perform high-speed printing and reduce costs.

  That is, since the output can be increased by the surface emitting laser or the surface emitting laser array of the present invention, high-speed printing is possible as compared with the image forming apparatus using the conventional surface emitting laser or the surface emitting laser array. Alternatively, the number of arrays can be reduced at the same speed as in the conventional case, the manufacturing yield of the surface emitting laser array chip can be greatly improved, and the cost of an image forming apparatus such as a laser printer can be reduced. Furthermore, the Al-free active layer makes it possible to achieve the same life as a surface emitting laser for communication such as an 850 nm band surface emitting laser, so that the optical writing optical unit itself can be reused, contributing to a reduction in environmental impact. it can.

(10th form)
According to a tenth aspect of the present invention, there is provided an optical pickup in which the surface emitting laser according to any one of the fourth to seventh aspects or the surface emitting laser array according to the eighth aspect is used as a light source. System.

  According to a tenth aspect of the present invention, the surface-emitting laser according to any one of the fourth to seventh aspects or the surface-emitting laser array according to the eighth aspect is used as a light source. Since it is an optical pickup system, it is possible to realize a handy type optical pickup system with high reliability and long-lasting power.

  That is, the wavelength of a semiconductor laser, which is a light source for optical writing and reproduction on a medium, is 780 nm for CD. Since surface-emitting lasers consume about an order of magnitude less power than edge-emitting semiconductor lasers, highly reliable, long-lasting, hand-held light that uses the 780 nm surface-emitting laser of the present invention as a light source for reproduction. A pickup system can be realized.

(Eleventh form)
In an eleventh aspect of the present invention, the surface-emitting laser according to any one of the fourth to seventh aspects or the surface-emitting laser array according to the eighth aspect is used as a light source. It is a module.

  According to an eleventh aspect of the present invention, the surface emitting laser according to any one of the fourth to seventh aspects or the surface emitting laser array according to the eighth aspect is used as a light source. Since it is an optical transmission module, an economical and high-speed optical transmission module can be realized.

  That is, in optical transmission using acrylic POF (plastic fiber), a surface emitting laser having an oscillation wavelength of 650 nm has been studied due to its absorption loss, but its high-temperature characteristics are poor and not practical. Therefore, although LEDs are currently used, high-speed modulation is difficult, and a semiconductor laser is necessary to realize high-speed transmission exceeding 1 Gbps.

  According to the surface emitting laser of the present invention having the shortest wavelength of 680 nm, the gain of the active layer is large, so that the output is high and the high-temperature characteristics are excellent. An economical and high-speed optical transmission module using a surface-emitting laser that is a cheap light source and POF that is a cheap optical fiber can be realized.

(Twelfth embodiment)
According to a twelfth aspect of the present invention, there is provided an optical transceiver characterized in that the surface emitting laser according to any one of the fourth to seventh aspects or the surface emitting laser array according to the eighth aspect is used as a light source. It is a module.

  According to a twelfth aspect of the present invention, the surface emitting laser according to any one of the fourth to seventh aspects or the surface emitting laser array according to the eighth aspect is used as a light source. Since it is an optical transceiver module, an economical and high-speed optical transceiver module can be realized.

  That is, in optical transmission using acrylic POF (plastic fiber), a surface emitting laser having an oscillation wavelength of 650 nm has been studied due to its absorption loss, but its high-temperature characteristics are poor and not practical. Therefore, although LEDs are currently used, high-speed modulation is difficult, and a semiconductor laser is necessary to realize high-speed transmission exceeding 1 Gbps.

  According to the surface emitting laser of the present invention having the shortest wavelength of 680 nm, the gain of the active layer is large, so that the output is high and the high-temperature characteristics are excellent. An economical and high-speed optical transceiver module using a surface emitting laser that is a cheap light source and POF that is a cheap optical fiber can be realized.

(13th form)
In a thirteenth aspect of the present invention, the surface emitting laser according to any one of the fourth to seventh aspects or the surface emitting laser array according to the eighth aspect is used as a light source. System.

  According to a thirteenth aspect of the present invention, the surface-emitting laser according to any one of the fourth to seventh aspects or the surface-emitting laser array according to the eighth aspect is used as a light source. Since it is an optical communication system, an economical optical communication system can be realized.

  That is, in optical transmission using acrylic POF (plastic fiber), a surface emitting laser having an oscillation wavelength of 650 nm has been studied due to its absorption loss, but its high-temperature characteristics are poor and not practical. Therefore, although LEDs are currently used, high-speed modulation is difficult, and a semiconductor laser is necessary to realize high-speed transmission exceeding 1 Gbps.

  The surface emitting laser of the present invention having a shortest wavelength of 680 nm has a high active layer gain, so it has high output and excellent high-temperature characteristics. The absorption loss of the fiber increases, but transmission is possible at short distances. An economical optical communication system using a surface emitting laser that is a cheap light source and POF that is a cheap optical fiber can be realized. Since it is extremely economical, it can be used as an optical communication system, particularly in a general home or office, or in equipment.

  FIG. 1 is a diagram showing an edge-emitting laser having a wavelength of 730 nm band according to Example 1 of the present invention. In the example of FIG. 1, a ridge stripe laser is used. The layer structure is a SCH-DQW (Separate Configuration Heterostructure Double Quantum Well) structure.

Referring to FIG. 1, an n-GaAs buffer layer, n- (Al _0.7 Ga _0.3 ) ₀ ... On an n- (100) GaAs substrate whose plane orientation is inclined by 10 ° in the (111) A plane direction _{. 5} In _0.5 P cladding layer, lower (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P light guide layer, consisting of two GaInPAs quantum well active layers and three GaInP barrier layers Active layer (multi-quantum well active layer), upper part (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P light guide layer, p- (Al _0.7 Ga _0.3 ) _0.5 In _{0 .5} P clad layer, p-GaInP intermediate layer, and p-GaAs contact layer are sequentially formed. Crystal growth was performed by MBE (molecular beam epitaxy) method.

  Then, except for the stripe region having a width of 3 μm, was removed to the middle of the p-AlGaAs cladding layer by photolithography and etching techniques to form a ridge structure. Then, a p-side electrode was formed on the ridge structure through an insulating film from which a portion to be a current injection portion was removed. An n-side electrode was formed on the back surface of the substrate.

  Here, the compressive strain amount of the GaInPAs quantum well active layer was 0.7%, and the tensile strain amount of the GaInP barrier layer was 1.6%. GaInP is a material whose band gap increases as the lattice constant decreases, that is, as the Ga composition increases.

  In Non-Patent Document 2 described above, when the growth temperature is 700 ° C. and the quantum well active layer has a compressive strain of 1.6%, if the tensile strain amount of the barrier layer is limited to 0.75% or more, the characteristics deteriorate. Was seen. That is, when the strain amount between the quantum well active layer and the barrier layer exceeds 2.35%, the characteristics deteriorate. In Example 1, since the compressive strain amount of the quantum well active layer is 0.7%, which is smaller than Non-Patent Document 2, the characteristics are not deteriorated even if the tensile strain amount of the barrier layer is increased to 1.6%. Good characteristics were obtained. By appropriately performing strain compensation in this way, the thickness of the lattice relaxation caused by strain can be increased, so the tolerance of the number of well layers and the thickness of the well layers is increased, and the target device characteristics are improved. There is an effect of increasing the degree of freedom in designing according to the design.

The band gaps Eg of GaInP with tensile strain amounts of 0.75% and 1.6% are 2.049 eV (Ga composition x = 0.62) and 2.239 eV (Ga composition x = 0.73), respectively. The band gap differences from the quantum well active layer (730 nm: 1.698 eV) are 351 meV and 541 meV, respectively, which are as large as 190 meV. On the other hand, in the structure of an 850 nm laser made of an AlGaAs-based material (the barrier layer Al composition x is set to 0.3 which is the largest among typical values), it is 356 meV. The band gap of the (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P cladding layer is 2.3 eV, and Al _x Ga has the largest band gap in the typical composition range of the AlGaAs cladding layer. Compared with _1-x As (x = 0.6, Eg = 2.0226 eV), both the band discontinuity between the quantum well active layer and the barrier layer and the band discontinuity between the quantum well active layer and the cladding layer are both present. Can be big. As described above, according to the present invention, it is understood that even when the wavelength is 730 nm, the carrier can be confined more sufficiently than the 850 nm laser made of an AlGaAs material.

  Further, in the edge-emitting laser of Example 1 of the present invention, the quantum well active layer has a compressive strain composition although it cannot be so large. When the distortion increases, the band separation between the heavy hole and the light hole increases, so that the gain increases and the threshold value is lowered and the efficiency is increased (high output). Since this effect cannot be realized with an AlGaAs cladding layer / AlGaAs active layer laser, the AlGaInP cladding layer / GaInPAs active layer of the present invention has a lower threshold than the 850 nm laser of the AlGaAs cladding layer / AlGaAs active layer. It can be seen that value conversion and high efficiency (high output) are possible.

Also, the optical guide layer using a _{(Al 0.5 Ga 0.5) 0.5 In} 0.5 P layer. The band gap is 2.2 eV. When an As-based material such as AlGaAs is formed on top of a P-based material such as AlGaInP or GaInPAs, P on the P-based material is replaced with As, and an As-rich material with a narrow band gap tends to be formed. Further, at the interface, In separation, such as In carry over to the AlGaAs layer, occurs. If this portion (that is, the AlGaAs layer) is between the active layer and the clad layer, a problem of absorption of light generated in the active layer occurs, leading to an increase in threshold value. Therefore, it is better not to insert an As-based material such as AlGaAs between the GaInPAs-based active layer and the AlGaInP cladding layer. In Example 1, since the interface between the P-based material and the As-based material is outside the cladding layer as viewed from the active layer and is away from the active layer, the problem of an increase in threshold does not occur.

  In the quaternary mixed crystal such as GaInPAs used in the quantum well active layer in Example 1, phase separation is likely to occur as the composition approaches the center, and it is not easy to obtain a good crystal. In order to obtain 730 nm or 780 nm with GaInPAs having a compressive strain composition, it becomes near the center of the quaternary mixed crystal, and as the amount of compressive strain increases, the crystal becomes more unstable and becomes more difficult. On the other hand, GaInP used for the barrier layer is a ternary mixed crystal, and crystal growth is much easier than that of a quantum well active layer made of GaInPAs. That is, it is easier to obtain a good crystal when the tensile strain amount of the barrier layer is larger than the compressive strain amount of the quantum well active layer.

  Further, when Al is contained in the active layer, there is a problem that oxygen that tends to become a non-radiative recombination center is easily taken in, the COD level is low, and high output cannot be obtained due to end face destruction, or the life is short. Since the active layer composed of the quantum well active layer and the barrier layer of Example 1 has an Al-free structure, high output and long life can be obtained.

  In addition, as in Patent Document 2, there are many examples of obtaining a 700 nm band with GaPAs, which is a ternary mixed crystal that facilitates crystal growth. GaAsP has a tensile strain, and it is necessary to increase the strain amount (the P composition is increased) as the wavelength is shorter. However, in order to obtain an Al-free active layer, a barrier layer having a large tensile strain as in the first embodiment. Cannot be used.

  As described above, according to the first embodiment, a 700 nm band semiconductor laser having excellent temperature characteristics, a low threshold value, a high output, and a long life could be obtained.

  When the semiconductor substrate is GaAs and any of GaAsP, AlGaAsP, GaInP, AlInP, GaInPAs, AlGaInP, and AlGaInPAs, which are materials having a composition that can increase the band gap as the lattice constant is decreased, By making the strain amount (tensile) of the barrier layer larger than the strain amount (compression) of the quantum well active layer, carrier confinement is improved as compared with the case where it is not. Further, when the semiconductor substrate is InP, when using any of GaInP, GaInAs, AlInAs, AlGaInAs, GaInPAs, AlGaInP, and AlGaInPAs, which is a material having a composition that can increase the band gap as the lattice constant is reduced, By making the amount of strain (tensile) larger than the amount of strain (compression) of the quantum well active layer, carrier confinement is improved as compared with the case where it is not. The material can be selected and designed as required, such as the oscillation wavelength.

  In the above example, an example of growth by the MBE method has been shown, but other growth methods such as MOCVD can also be used. Moreover, although the example of the double quantum well structure (DQW) was shown as a laminated structure, the quantum well structure which made the number of other wells can also be used. Also, the structure of the laser may be another structure. Further, although an example of an end face type semiconductor laser has been shown, a light emitting diode (LED) may be used, and an LED (end face type, surface emitting type) having high light emission efficiency, good temperature characteristics, and a long lifetime can be obtained. .

  2 and 3 are diagrams showing a surface emitting laser according to Embodiment 2 of the present invention. FIG. 3 is a view showing a cross-sectional structure around the active layer of the surface emitting laser shown in FIG.

In the surface emitting laser of Example 2, n-Al _0.9 Ga _0.1 As and n − are formed on an n- (100) GaAs substrate whose plane orientation is inclined at an inclination angle of 15 ° in the (111) A plane direction. An n-semiconductor distributed Bragg reflector (first reflector) having a periodic structure in which Al _0.3 Ga _0.7 As and the like are alternately laminated with a thickness of 1/4 times the oscillation wavelength in the medium, for example, 35.5 periods. : N-side DBR) is formed (details are omitted in FIG. 2). In addition, between the n-Al _0.9 Ga _0.1 As and the n-Al _0.3 Ga _0.7 As, the thickness of 20 nm is obtained by gradually changing the Al composition from one value to the other value. A composition gradient layer is inserted, and the thickness including the gradient layer is ¼ times the oscillation wavelength in the medium. According to this, when electricity is supplied to the DBR, the band discontinuity between the two can be smoothed, and the increase in resistance can be suppressed.

Then, a lattice-matched (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P lower first spacer (cladding) layer is lattice-matched (Al _0.5 Ga) on the first reflecting mirror. _0.5 ) _0.5 In _0.5 P lower second spacer layer, 1.0% compressive strain composition, three GaInPAs well layers with a wavelength of 780 nm, and 1.2% tensile strain composition A quantum well active layer composed of a certain four-layer Ga _0.68 In _0.32 P barrier layer, (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P upper second spacer layer, (Al _{0 .7} Ga _0.3 ) _0.5 In _0.5 P upper first spacer (cladding) layer is formed. Further, a periodic structure in which, for example, 25 cycles of p-Al _x Ga _1-x As (x = 0.9) and p-Al _x Ga _1-x As (x = 0.3) are alternately stacked. A p-semiconductor distributed Bragg reflector (second reflector: p-side DBR) is formed (details are omitted in FIG. 2). Similar to the first reflecting mirror, a composition gradient layer is also inserted into the second reflecting mirror. A p-GaAs contact layer that contacts the electrode is formed on the top. A thickness corresponding to one wavelength of the oscillation wavelength (so-called lambda cavity) was set between the first reflecting mirror and the second reflecting mirror.

The surface emitting laser of Example 2 is manufactured as follows. That is, crystal growth was performed by MOCVD. TMG (trimethylgallium), TMA (trimethylaluminum), TMI (trimethylindium), PH ₃ (phosphine), AsH ₃ (arsine) are used as raw materials, and H ₂ Se (hydrogen selenide) is used as an n-type dopant. DMZn (dimethyl zinc) and CBr ₄ were used as p-type dopants. Further, the carrier gas was used H _2. The MOCVD method is more suitable than the MBE method as a crystal growth method of a surface emitting laser including DBR because a composition gradient layer can be easily formed by controlling the supply amount of the source gas. Further, high vacuum is not required as in the MBE method, and the supply flow rate and supply time of the source gas may be controlled, so that the mass productivity is excellent.

In Example 2, a part of the low refractive index layer close to the active layer in the p-side DBR was an AlAs layer. Then, a mesa having a predetermined size was formed by exposing at least the side surface of the p-AlAs selective oxidation layer, and the AlAs that appeared on the side surface was oxidized from the side surface with water vapor to form an Al _x O _y current narrowing portion. Then, the etching part is buried and planarized with polyimide, the polyimide on the upper reflecting mirror having the p contact part and the light emitting part is removed, and a p-side electrode is formed in addition to the light emitting part on the p contact layer, An n-side electrode was formed on the back surface of the substrate.

  In Example 2, since the current was narrowed by selective oxidation of the selective oxidation layer containing Al and As as main components, the threshold current was low. In a current narrowing structure using a current narrowing layer made of an Al oxide film that selectively oxidizes the selective oxidation layer, the current spreading can be suppressed by forming the current narrowing layer close to the active layer, and a minute region that does not touch the atmosphere It is possible to confine carriers efficiently. Furthermore, the refractive index is reduced by oxidizing it into an Al oxide film, and light can be efficiently confined in a minute region where carriers are confined by the effect of the convex lens, resulting in extremely high efficiency and a reduced threshold current. Is done. In addition, since the current narrowing structure can be easily formed, the manufacturing cost can be reduced.

  In the surface emitting laser of Example 2, an AlGaInP material is used for the spacer layer, and GaInPAs is used for the barrier layer and the quantum well active layer. And, by forming on the (100) GaAs substrate whose plane orientation is inclined by 15 ° in the (111) A plane direction, the surface property of the surface due to the reduction of the band gap due to the formation of the natural superlattice and the generation of hillocks (hill-like defects) The effects of deterioration and non-radiative recombination centers are reduced.

  That is, for AlGaInP and GaInP, a (100) GaAs substrate whose plane orientation is inclined at an angle (inclination angle) within the range of 5 ° to 20 ° in the (111) A plane direction is suitable. When close to the (100) plane, the band gap decreases due to the formation of a natural superlattice, the surface property deteriorates due to the generation of hillocks (hill-like defects), and non-radiative recombination centers occur. Adversely affect. On the other hand, when it is inclined from the (100) plane toward the (111) A plane, the formation of the natural superlattice is suppressed according to the inclination angle. In other words, the band gap changes abruptly when the tilt angle is about 10 ° to 15 °, and then gradually approaches the normal band gap (the value of a completely mixed crystal), and hillocks are also generated gradually. I will not. However, when the inclination angle in the (111) A plane direction exceeds 20 °, crystal growth becomes difficult. Therefore, in the AlGaInP material used in the material system of the red laser (630 nm to 680 nm), the angle is in the range of 5 ° to 20 ° (more often, the angle is in the range of 7 ° to 15 °). An inclined substrate is generally used. This applies not only to AlGaInP, which is a spacer layer (cladding layer), but also to the case where the barrier layer is GaInP as in the example of Table 1 described later. Furthermore, even if the barrier layer and the quantum well active layer are made of GaInPAs, there is a concern about adverse effects. Therefore, the growth of these materials has a plane orientation in the range of 5 ° to 20 ° in the (111) A plane direction. It is preferable to use a (100) GaAs substrate that is inclined at an angle (more preferably at an angle in the range of 7 ° to 15 °).

  Further, the following table (Table 1) shows a spacer layer, a well layer, and a barrier layer having typical material compositions of an AlGaAs (spacer layer) / AlGaAs (quantum well active layer) system 780 nm and 850 nm surface emitting laser. The band gap difference with the well layer is shown. At the same time, the band gap difference between the spacer layer and the well layer and the barrier layer and the well layer, which are examples of the AlGaInP (spacer layer) / GaInPAs (quantum well active layer) 780 nm surface emitting laser of the present invention is shown. . The GaInPAs barrier layer shows an example with a Ga composition of 0.68 (tensile strain of 1.2%).

In Example 2, (Al _0.7 Ga) _0.5 In _0.5 P having a wide band gap is used as the spacer layer (cladding layer). By using (Al _a Ga _1-a ) _b In _1-b P (0 <a ≦ 1, 0 ≦ b ≦ 1) for at least part of the spacer layer, the spacer layer is made of AlGaAs. Thus, the band gap difference between the spacer layer and the quantum well active layer can be made extremely large. The band gap difference between the spacer layer and the quantum well active layer is 743 meV, which is very large, compared to 466 meV (when the Al composition is 0.6) when the spacer layer is formed of AlGaAs. As shown in the first embodiment, the band gap difference between the barrier layer and the quantum well active layer similarly has a superior difference, resulting in good carrier confinement.

  As shown in Table 1, the AlGaInP (spacer layer) / GaInPAs (quantum well active layer) type 780 nm surface emitting laser is not only the AlGaAs / AlGaAs type 780 nm surface emitting laser but also the AlGaAs / AlGaAs type 850 nm surface emitting laser. However, it can be seen that a large band gap difference can be obtained.

  In addition, since the quantum well active layer has a compressive strain, the increase in gain is increased by band separation of heavy holes and light holes. Because of these high gains, the surface emitting laser of Example 2 had high output at a low threshold.

  The quantum well active layer and the barrier layer are made of a material that does not contain Al. That is, since the Al-free active region (quantum well active layer and adjacent layer) is used, the oxygen uptake is reduced and the formation of a non-radiative recombination center can be suppressed, and the lifetime is long.

  In addition, the polarization direction control in the surface emitting laser according to the second embodiment utilizes the optical gain anisotropy due to the tilt of the substrate. The optical gain anisotropy is small because the inclination angle is small (15 °) as compared with the case where the (311) B substrate (inclination angle is 25 °), which is currently regarded as the most prominent, is used. In Example 2, since this decrease was compensated by an increase in optical gain anisotropy by applying compressive strain to the quantum well active layer, the polarization direction could be controlled.

  Thus, according to Example 2, it is possible to realize a highly reliable 780 nm surface emitting laser with a large active layer gain, a low threshold value, a high output, and a polarization direction controlled. did it.

  Further, in the surface emitting laser of the present invention, the confinement of carriers is improved, and the reflectivity of the light extraction side DBR can be reduced by lowering the threshold by increasing the gain by the strained quantum well active layer. Therefore, it is possible to further increase the output.

The effect of using the wide gap spacer layer and the wide gap barrier layer of the present invention to improve the carrier confinement from the 780 nm band by the AlGaAs-based material becomes smaller as the wavelength becomes shorter, but may be longer than 680 nm. If you can get. _{Al x Ga 1-x As (} 0 <x ≦ 1) based most bandgap routine composition range of the spacer layer is larger _{Al x Ga 1-x As (} x = 0.6, Eg = 2.0226eV) and The band gap difference from the active layer having a composition wavelength of 780 nm (Eg = 1.5567 eV) is (Al _a Ga _1-a ) _b In _1-b P (0 <a ≦ 1, 0 ≦ b ≦ 1) of the spacer layer. (Al _a Ga _1-a ) _b In _1-b P (a = 0.7, b = 0.5, Eg = 2.289 eV) and composition wavelength 680 nm (Eg) = 1.8233 eV) and the band gap difference (460 meV) from the active layer. Regarding the band gap difference between the barrier layer and the quantum well active layer, for example, the barrier layer is Ga _e In _1-e P _f As _1-f (e = 0.6, f = 1, Eg = 2.02 eV). In this case, the band gap difference from the active layer having a composition wavelength of 680 nm is about 200 meV, which is almost the same as that of a 780 nm surface emitting laser using an AlGaAs / AlGaAs active layer. Can also increase the band gap difference.

  That is, by using an AlGaInP-based spacer layer, if the composition wavelength is longer than 680 nm, even if an Al-free active layer (quantum well active layer and barrier layer) is used, the 780 nm surface by the AlGaAs / AlGaAs-based active layer Carrier confinement equivalent to or higher than that in the case of a light emitting laser is possible, and the effect of the strained quantum well active layer is further added, so that characteristics equal to or higher than that can be obtained.

In addition, even if it is shorter than 680 nm, it can be set as an Al free active layer. As a red laser material having an oscillation wavelength of 600 nm to 700 nm, an AlGaInP spacer layer (cladding layer), an AlGaInP barrier layer, and a GaInP quantum well active layer are used. (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P is often used for the barrier layer, and the band gap is about 2.2 eV. The band gap of GaInP having a large tensile strain composition as in the present invention is, for example, 2.239 eV with a Ga composition of 0.73, and can be used unless the amount of compressive strain in the quantum well active layer is increased. Thereby, the lifetime of the red laser can also be improved.

  FIG. 4 is a top view of a surface emitting laser according to Embodiment 3 of the present invention.

  The difference between Example 3 and Example 2 is that the mesa shape viewed from the light emitting direction of the surface emitting laser was formed with anisotropy so as to be a long oval shape in the (111) A plane direction. It is. This may be another shape such as a rectangle. As a result, the shape of the current injection region formed by the Al oxide film also became long in the (111) A plane direction.

  The control of the polarization direction in the surface emitting laser of the present invention mainly utilizes the optical gain anisotropy due to the tilt of the substrate. Compared to the case of using the (311) B substrate (inclination angle is 25 °), which is currently regarded as the most promising, the inclination angle is small (15 °), so that the substrate cost can be suppressed and the cleavage is easy to handle. Although the easiness is improved, the optical gain anisotropy is reduced. In Example 3, this decrease is increased in the optical gain anisotropy by applying compressive strain to the quantum well active layer, and is further anisotropic in the outer peripheral shape of the active layer viewed from the light emitting direction of the surface emitting laser. It is compensated by increasing the optical gain in the substrate tilt direction ((111) A plane direction) by having a long shape in the (111) A plane direction, which is inferior to (311) B substrate utilization. There was no polarization direction control.

  As described above, according to the third embodiment, the active layer has a large gain, a low threshold value, a high output, excellent reliability, and the polarization direction is controlled at the same time. A filled 780 nm surface emitting laser could be realized.

  FIG. 5 is a diagram showing a surface emitting laser array according to Example 4 of the present invention. That is, FIG. 5 is a top view of the surface emitting laser array chip of the fourth embodiment.

  In the example of FIG. 5, the surface emitting lasers 10 of Example 3 are arranged one-dimensionally. However, in Example 4, p and n of the surface emitting laser were reversed from those of the surface emitting laser of Example 2. That is, in Example 4, the surface emitting laser is formed on the p-type GaAs semiconductor substrate, and the n-side individual electrode is formed on the upper surface and the p-side common electrode is formed on the back surface. In the example of FIG. 5, a plurality of surface emitting lasers are arranged one-dimensionally. However, for example, a plurality of surface emitting lasers may be integrated two-dimensionally as shown in FIG.

  Since the surface emitting laser is of the surface emitting type, it is easy to form an array, and since it is formed by a normal semiconductor process, the element position system is high. Furthermore, by integrating a large number of surface-emitting lasers whose polarization direction is controlled in a constant direction as in the present invention on the same substrate, when applied to a writing optical system, simultaneous writing with multiple beams is possible. Indentation is facilitated, the writing speed is remarkably improved, and printing can be performed without reducing the printing speed even if the writing dot density increases. Also, when the writing dot density is the same, the printing speed can be increased. In addition, when applied to communication, data transmission by multiple beams can be performed at the same time, so high-speed communication can be performed. Further, the surface emitting laser operates with low power consumption, and particularly when incorporated in a device, the temperature rise can be reduced.

  FIG. 6 is a diagram showing an optical transmission module according to Embodiment 5 of the present invention. The optical transmission module of FIG. 6 is a combination of a surface emitting laser array chip of the present invention and an inexpensive acrylic POF (plastic optical fiber). It has become a thing. The active layer composition has an oscillation wavelength of 680 nm. In the optical transmission module of the fifth embodiment, laser light from the surface emitting laser is input to the POF and transmitted. Acrylic POF has a bottom of absorption loss at 650 nm, and a surface-emitting laser of 650 nm has been studied. Conventionally, an LED is used in such a light transmission module, but in this case, high-speed modulation is difficult, and a semiconductor laser is necessary to realize high-speed transmission exceeding 1 Gbps.

  The surface emitting laser used in the optical transmission module of Example 5 has a wavelength of 680 nm, but since the active layer gain is large, the output power is high and the high temperature characteristics are excellent, and the absorption loss of the fiber is large but short. Transmission is possible at a distance.

  In the field of optical communications, parallel transmission using a laser array in which a plurality of semiconductor lasers are integrated has been attempted in order to transmit more data at the same time. As a result, high-speed parallel transmission is possible, and more data than before can be transmitted simultaneously.

  In the fifth embodiment (that is, in the example of FIG. 6), each surface emitting laser element of the surface emitting laser array and the optical fiber are associated with each other on a one-to-one basis. It is also possible to further increase the transmission rate by arranging in a two-dimensional or two-dimensional array and performing wavelength multiplexing transmission.

  Further, since the inexpensive surface emitting laser element according to the present invention and the inexpensive POF are combined, a low-cost optical transmission module can be realized, and a low-cost optical communication system using this can be realized. In other words, since it is extremely low cost, it is effective for short-distance data communication for home use, office indoor use, and device use.

  FIG. 7 is a diagram showing an optical transceiver module according to Embodiment 6 of the present invention. The optical transceiver module of FIG. 7 includes the surface emitting laser element of Embodiment 2, a receiving photodiode, and an acrylic POF. It is a combination. Note that the surface emitting laser element has an active layer composition with a wavelength of 680 nm.

  When the surface emitting laser element according to the present invention is used in an optical communication system, the surface emitting laser element and POF according to the present invention are low in cost, and therefore, as shown in FIG. It is possible to realize a low-cost optical communication system using an optical transmission / reception module that combines a photodiode for use with a POF. In addition, since the POF has a large fiber diameter and can be easily coupled with the fiber to reduce the mounting cost, it is possible to realize a very low cost module. Since it is extremely economical, it is particularly effective to use it in an optical communication system such as in a general home or office, or in equipment.

  In optical transmission using acrylic POF (plastic fiber), a surface-emitting laser having an oscillation wavelength of 650 nm has been studied due to its absorption loss. Therefore, although LEDs are currently used, high-speed modulation is difficult, and a semiconductor laser is necessary to realize high-speed transmission exceeding 1 Gbps.

  According to the surface emitting laser of the present invention having an oscillation wavelength of 680 nm, since the active layer gain is large, it has high output and excellent high temperature characteristics, generates less heat, and can be used without cooling to high temperatures. A system can be realized. Although the absorption loss of the fiber increases, transmission is possible over a short distance.

  As an optical communication system using the surface emitting laser element according to the present invention, transmission between devices such as a LAN (Local Area Network) using an optical fiber, data transmission between boards in a device, LSI in a board, etc. In particular, it can be used for short-distance communication as an optical interconnection between elements in an LSI.

  In recent years, the processing performance of LSIs and the like has improved, but the transmission speed of the part connecting them will become a bottleneck in the future. When the signal connection in the system is changed from the conventional electrical connection to the optical interconnect, for example, the optical transmission module or the optical transmission / reception module according to the present invention is used between the boards of the computer system, between the LSIs in the board, between the elements in the LSI, etc. Connection, an ultra-high-speed computer system becomes possible.

  In addition, when a plurality of computer systems are connected using the optical transmission module or the optical transmission / reception module according to the present invention, an ultra-high speed network system can be constructed. In particular, the surface emitting laser element is suitable for a parallel transmission type optical communication system because it can reduce power consumption by an order of magnitude compared to the edge emitting laser and can easily form a two-dimensional array.

  FIG. 8 is a diagram showing a laser printer according to a seventh embodiment of the present invention. In the laser printer of Example 7, the surface emitting laser of Example 3 is used. That is, FIG. 8 is a schematic diagram of the optical scanning portion of a laser printer in which a 4 × 4 two-dimensional surface emitting laser array chip having a wavelength of 780 nm is combined with a photosensitive drum. FIG. 9 is a diagram (top view) showing a schematic configuration of a surface emitting laser array chip used in the laser printer of FIG. By adjusting the lighting timing, this surface emitting laser array chip can be regarded as having the same configuration as the case where light sources are arranged at intervals of 10 μm in the sub-scanning direction on the photosensitive member as shown in FIG.

  In the seventh embodiment, a plurality of beams separated from the surface-emitting laser array in the sub-scanning direction by adjusting the timing of lighting the dot position by rotating the scanning polygon mirror at high speed using the same optical system. As a spot, light is condensed on a photoconductor as a surface to be scanned, and a plurality of beams are scanned at a time (that is, a plurality of beams are scanned at a time).

  Since the surface emitting laser array of the present invention can control the polarization direction and increase the output, printing can be performed at a higher speed than a laser printer using a conventional surface emitting laser array. Alternatively, the number of arrays can be reduced at the same speed as in the conventional case, the manufacturing yield of the surface emitting laser array chip can be greatly improved, and the cost of the laser printer can be reduced.

  According to the seventh embodiment, writing can be performed on the photosensitive member at intervals of about 10 μm in the sub-scanning direction, which corresponds to 2400 DPI (dots / inch). Further, the writing interval in the main scanning direction can be easily controlled by the lighting timing of the light source. 16 dots could be written simultaneously, and high-speed printing was possible. Higher-speed printing is possible by increasing the number of arrays. Further, by adjusting the interval between the surface emitting laser elements, the interval in the sub-scanning direction can be adjusted, and the density can be made higher than 2400 DPI, thereby enabling higher quality printing. Since the surface emitting laser according to Example 7 has a higher output than the conventional surface emitting laser, the printing speed can be made faster than the conventional one.

  Furthermore, the Al-free active layer makes it possible to achieve a life equivalent to a surface emitting laser for communication such as an 850 nm band surface emitting laser (room temperature estimated at 1 million hours has been reported). It can be reused and contributes to reducing environmental impact.

  Although the application example to the laser printer is shown in the seventh embodiment, the surface emitting laser or the surface emitting laser array of the present invention can be used as a light source for recording and reproducing such as a CD.

The wavelength of a semiconductor laser that is a light source for optical writing and reproduction on a medium is 780 nm for CD. The surface-emitting laser has a long lifetime, and the surface-emitting laser consumes about one digit less power than the edge-emitting semiconductor laser. Therefore, the surface-emitting laser of 780 nm according to the present invention is a reliable light source for reproduction. It is possible to realize a handy type optical pickup system that is high in power and lasts long.

It is a figure which shows the edge-emitting type laser of wavelength 730nm band concerning Example 1 of this invention. It is a figure which shows the surface emitting laser which concerns on Example 2 of this invention. It is a figure which shows the surface emitting laser which concerns on Example 2 of this invention. It is a top view of the surface emitting laser which concerns on Example 3 of this invention. It is a figure which shows the surface emitting laser array which concerns on Example 4 of this invention. It is a figure which shows the optical transmission module which concerns on Example 5 of this invention. It is a figure which shows the optical transmission / reception module which concerns on Example 6 of this invention. It is a figure which shows the laser printer of Example 7 of this invention. It is a figure which shows the example of the surface emitting laser array chip | tip which integrated the several surface emitting laser in two dimensions.

Claims (13)

In a semiconductor light emitting device in which a lower clad layer, a lower light guide layer, an active layer, an upper light guide layer, and an upper clad layer are formed on a GaAs substrate, the active layer includes Ga _c In _1-c P _d As _1-d (0 <c <1, 0 ≦ d ≦ 1) compression strain quantum well active layer and Ga _e In _1-e P _f As _1-f (0 <e ≦ 1, 0 ≦ f ≦ 1) It has a tensile strain barrier layer, and at least a part of at least one of the lower clad layer and the upper clad layer has a larger band gap energy than the active layer (Al _a Ga _1-a ) _b In _1-b P (0 <a ≦ 1, 0 <b <1) layer is used, and the absolute value of the strain amount of the barrier layer is larger than the absolute value of the strain amount of the quantum well active layer. A semiconductor light emitting device characterized by the above. 2. The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device has an oscillation wavelength longer than about 680 nm. 3. The semiconductor light emitting device according to claim 1, wherein the plane orientation of the GaAs substrate is a (100) plane inclined at an angle in the range of 5 ° to 20 ° with respect to the (111) A plane direction. A semiconductor light emitting device. An active layer having at least one quantum well active layer and a barrier layer for generating laser light on a GaAs substrate, and an upper spacer layer and a lower spacer made of at least one material provided above and below the active layer In a surface emitting laser including a resonator region including a layer and upper and lower reflecting mirrors provided above and below the resonator region, the upper reflecting mirror and the lower reflecting mirror have a periodic refractive index. And a semiconductor distributed Bragg reflector that reflects incident light by light wave interference, and at least part of the semiconductor distributed Bragg reflector has a refractive index of Al _x Ga _1-x As (0 <x ≦ 1). and small becomes _{layer, Al y Ga 1-y as} (0 ≦ y <x ≦ 1) consisting of a refractive index consists of a large consisting layer of the upper spacer layer and the lower spacer layer at least one of At least a portion of the pacer _{layer, (Al a Ga 1-a} ) b In 1-b P (0 <a ≦ 1,0 <b <1) is used, Ga is the quantum well active layer having a compressive strain _c In _1-c P _d As _1-d (0 <c <1, 0 ≦ d ≦ 1) and the barrier layer has tensile strain Ga _e In _1-e P _f As _1-f (0 <e ≦ 1, 0 ≦ f ≦ 1), and the absolute value of the strain amount of the barrier layer is larger than the absolute value of the strain amount of the quantum well active layer. 5. The surface emitting laser according to claim 4, wherein the surface emitting laser has an oscillation wavelength longer than about 680 nm. 6. The surface emitting laser according to claim 4, wherein the plane orientation of the GaAs substrate is a (100) plane inclined at an angle in the range of 5 ° to 20 ° with respect to the (111) A plane direction. Surface emitting laser. 7. The surface emitting laser according to claim 6, wherein the outer peripheral shape of the active layer viewed from the light emitting direction has anisotropy that is long in the (111) A plane direction. . A surface-emitting laser array comprising a plurality of surface-emitting lasers according to any one of claims 4 to 7 formed on the same substrate. An image forming apparatus, wherein the surface emitting laser according to any one of claims 4 to 7 or the surface emitting laser array according to claim 8 is used as a writing light source. An optical pickup system, wherein the surface emitting laser according to any one of claims 4 to 7 or the surface emitting laser array according to claim 8 is used as a light source. An optical transmission module, wherein the surface-emitting laser according to any one of claims 4 to 7 or the surface-emitting laser array according to claim 8 is used as a light source. An optical transceiver module, wherein the surface-emitting laser according to claim 4 or the surface-emitting laser array according to claim 8 is used as a light source. An optical communication system, wherein the surface-emitting laser according to any one of claims 4 to 7 or the surface-emitting laser array according to claim 8 is used as a light source.

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