JP2007027364A - P-type semiconductor distribution bragg reflector, surface emitting element, surface emitting monolithic array, electrophotograph system, optical communication system and optical interconnection system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly reliable p-type semiconductor distribution Bragg reflector having the excellent optical characteristic (reflectivity) and electric characteristic (low resistance electric characteristic) particularly in the short-wavelength band. <P>SOLUTION: In the p-type semiconductor distribution Bragg reflector in which a high refractive index layer is constituted with a AlGaInP layer, a low refractive index layer is constituted with a AlGaAs layer, and two kinds of layers include p-type impurity element. The p-type impurity element is Mg as included at least in the AlGaInP layer among two kinds of layer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a p-type semiconductor distributed Bragg reflector, a surface light emitting element, a surface light emitting monolithic array, an electrophotographic system, an optical communication system, and an optical interconnection system.

  Conventionally, surface emitting laser elements (VCSEL) and resonator resonant surface emitting diode elements (RCLED) are known as surface emitting semiconductor elements (surface emitting elements) that can output in a direction perpendicular to the substrate surface. Yes. These surface light emitting devices include, for example, an active layer having a (multiple) quantum well structure, a resonator spacer layer provided on both sides of the active layer, and a pair of semiconductor multilayers provided on both sides of the resonator spacer layer. The pair of semiconductor distributed Bragg reflectors are doped with impurities of p-type and n-type, respectively, and are provided on the outer side of the semiconductor distributed Bragg reflector. By applying a voltage to the electrodes, carriers (holes, electrons) are injected into the active layer, and laser oscillation and light emission occur due to light emission recombination.

  Here, in particular, since the surface emitting laser element has a thin gain region (active layer) in the laser oscillation direction, a resonator mirror having a high reflectance of 99% or more is required to obtain oscillation. As such a mirror, the above-mentioned semiconductor distributed Bragg reflector is suitable. The semiconductor distributed Bragg reflector has two types of semiconductor layers with different refractive indexes stacked alternately with a thickness of λ / 4n (n is the refractive index of the semiconductor layer at the wavelength λ) with respect to the target wavelength (λ). Thus, it is possible to obtain a high reflectance by multiple reflection of light waves. At this time, the higher the difference in refractive index between the two types of semiconductor layers and the greater the number of stacked layers, the higher the reflectance can be obtained.

As a configuration of the semiconductor distributed Bragg reflector, a configuration using an AlGaAs-based material is widely known, and is configured using a semiconductor material that becomes transparent according to the oscillation wavelength in order to prevent absorption of oscillation light. For example, Non-Patent Document _1, the In _0.2 Ga 0.8 As / GaAs and the active layer, examples of 980nm band surface-emitting laser element of the AlAs / GaAs was distributed Bragg reflector material are shown.

  In order to obtain a high reflectance in a semiconductor distributed Bragg reflector, it is desirable that the refractive index difference between the two types of semiconductor layers constituting the semiconductor distributed Bragg reflector is large. This is a desirable combination that can obtain the highest reflectivity as a combination.

  However, in general, in the same kind of semiconductor material, the refractive index has a corresponding relationship with the band gap energy in the direct transition, and the band gap energy difference tends to increase as the combination increases in the refractive index difference. At the interface (heterostructure) between two types of semiconductor layers with different band gap energies, a potential barrier is formed due to band discontinuity of each band (conduction band, valence band), and conduction of carriers is hindered. There is a problem of resistance. In particular, in the p-type semiconductor material, the increase in resistance is significant, and there is a problem that the element becomes high resistance due to the series resistance in the p-type semiconductor distributed Bragg reflector.

  As a method of suppressing this increase in resistance, it is known to provide a hetero spike buffer layer such as an intermediate layer or a composition gradient layer at the interface between two types of semiconductor layers constituting a p-type semiconductor distributed Bragg reflector. Here, the intermediate layer is a layer having a composition between two types of semiconductor layers constituting the p-type semiconductor distributed Bragg reflector. In addition, the composition gradient layer is a layer in which the composition of the semiconductor layer is gradually changed from one to the other of the two types of semiconductor layers, and by providing these, generation of a potential barrier at the heterointerface can be suppressed. Are known. The element of Non-Patent Document 1 described above has a configuration in which the hetero spike buffer layer is provided in order to reduce the resistance of the p-type semiconductor distributed Bragg reflector.

  However, in order to obtain a high reflectance, it is desirable that the interface between the two layers constituting the p-type semiconductor distributed Bragg reflector is steep. In the above example, although the electrical resistance is reduced by the composition gradient layer, At the same time, the reflectance also decreases.

  On the other hand, in the short wavelength band, light absorption by the material constituting the semiconductor distributed Bragg reflector occurs, so that the materials that can be used for the semiconductor distributed Bragg reflector are limited. For example, GaAs is used as a high refractive index material for a semiconductor distributed Bragg reflector in the long wavelength band, but absorbs incident light in a shorter wavelength band than 870 nm corresponding to the band gap energy. It cannot be used as a material for semiconductor distributed Bragg reflectors.

  In such a case, it is necessary to use an AlGaAs mixed crystal that is sufficiently transparent with respect to the reflection wavelength (oscillation wavelength) and has an Al composition as small as possible as the high refractive index layer.

As an example of the semiconductor distributed Bragg reflector in the short wavelength band, for example, in Non-Patent Document 2, Al _0.12 Ga _0.88 As / Al _0.3 Ga _0.7 As is used as the active layer material, and Al _{0 .9} Ga _0.1 As / Al _0.3 Ga _0.7 As is an example of a 780 nm band surface emitting laser element using a distributed Bragg reflector material. _0.54 In _0.46 P / (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P is used as the active layer material, and AlAs / Al _0.5 Ga _0.5 As is a distributed Bragg reflector. An example of a 670 nm-band surface emitting laser element as the material of is shown.

  In particular, in the visible band, it is known to use an AlGaInP-based material in addition to the above-described AlGaAs-based material as a material for a semiconductor distributed Bragg reflector. For example, Patent Document 1 discloses an emission wavelength of 610 nm. In the resonator resonant surface light emitting diode element, an example is disclosed in which the distributed Bragg reflector on the substrate side is made of an AlGaInP material, and the distributed Bragg reflector on the light emitting side is made of an AlGaAs-based material.

  In the short wavelength band, the band discontinuity tends to be smaller in this way, and the problems related to electrical resistance are alleviated, but conversely, it becomes difficult to obtain a sufficient refractive index difference, and optical (reflection) ) There is a problem that the characteristics deteriorate. Further, as the wavelength is shortened, the thickness of the constituent layer of the distributed Bragg reflector is also reduced, so that the influence of the composition gradient layer on the reflectance is larger than that in the long wavelength band.

  To deal with these problems, Non-Patent Document 4 shows an example in which a distributed Bragg reflector having a steep hetero interface in a short wavelength region and having low electrical resistance and excellent optical characteristics is configured. Yes.

  That is, in this Non-Patent Document 4, paying attention to the valence band energies of the AlGaInP material and the AlGaAs material, a composition in which the valence band energy difference is reduced from two mixed crystals is combined, and has a steep hetero interface, It has been reported that a p-type semiconductor distributed Bragg reflector with low electrical resistance has been obtained.

Specifically, in Non-Patent Document 4, a p-AlGaInP / AlGaAs distributed Bragg reflector using Be as a p-type impurity element is manufactured using a gas source molecular beam epitaxy (GSMBE) method. Here, the reflection wavelength (the wavelength at which the reflectivity is highest) is set to 650 nm, which is the wavelength at which the absorption loss in the plastic optical fiber (POF) is lowest, and is actually a distributed Bragg having a peak reflection wavelength at 638 nm. A reflector is manufactured. The specific composition of the distributed Bragg reflector is (Al _0.27 Ga _0.73 ) _0.52 In _0.48 P / Al _0.9 Ga _0.1 As. In the example of Non-Patent Document 4, the above configuration realizes a p-type semiconductor distributed Bragg reflector having an extremely low resistance while being a steep hetero interface in a short wavelength band.
IEEE Photon. Technol. Lett Vol. 7, no. 11, 1995, p. p. 1234 IEEE Photon. Technol. Lett. Vol. 11, no. 12, 1999, p. p. 1539 IEEE Photon. Technol. Lett. Vol. 6, no. 3, 1994, p. p. 313 JP 2002-204026 A Applied physics letters vol. 74, p. p. 3758, 1999

  As described above, Non-Patent Document 4 realizes a semiconductor distributed Bragg reflector having a low electrical resistance and a high reflectivity by using a combination of an AlGaInP-based material and an AlGaAs-based material as a material for a semiconductor distributed Bragg reflector. However, there is no mention of the characteristics (optimum composition range) with respect to the wavelength, and the fabrication is merely performed by setting the reflection wavelength to the 650 nm band, and detailed examination in other wavelength ranges is performed. Not.

  Further, an example in which the MBE method is used as a crystal growth method is shown, and there is no mention of a problem or the like in the case where crystal growth is performed by an MOCVD method excellent in mass productivity such as throughput.

  As described above, there are many other items to be examined, and it is difficult to produce a p-type semiconductor distributed Bragg reflector with excellent characteristics only from the conventional technique including Non-Patent Document 4.

  The present invention provides a highly reliable p-type semiconductor distributed Bragg reflector having excellent optical characteristics (reflectance) and excellent electrical characteristics (low resistance electrical characteristics), particularly in a short wavelength region. It is aimed.

  Another object of the present invention is to provide a surface light emitting device, a surface light emitting monolithic array, an electrophotographic system, an optical communication system, and an optical interconnection system that have a low driving voltage and can operate at a high output particularly in a short wavelength band. Yes.

  To achieve the above object, according to the present invention, the high refractive index layer is composed of an AlGaInP layer, the low refractive index layer is composed of an AlGaAs layer, and the two types of layers contain a p-type impurity element. The p-type semiconductor distributed Bragg reflector is characterized in that the p-type impurity element in at least the AlGaInP layer of the two types of layers is Mg.

The invention described in claim 2 is composed of a high refractive index layer made of (Al _x2 Ga _1-x2 ) _y2 In _1-y2 P layer and a low refractive index layer made of Al _x1 Ga _1-x1 As layer, In the p-type semiconductor distributed Bragg reflector in which the two types of layers contain a p-type impurity element, the reflection wavelength of the p-type semiconductor distributed Bragg reflector is shorter than 635 nm, and further, the Al _x1 Ga _1-x1 As The composition of the layer is in the range of 0.95 ≦ x1 ≦ 1, and the (Al _x2 Ga _1-x2 ) _y2 In _1-y2 P layer is lattice-matched to the GaAs substrate, and the composition is x2 ≧ 0.35, It is characterized by a range of 0 <y2 <1.

  A third aspect of the present invention is a surface light emitting device comprising the p-type semiconductor distributed Bragg reflector according to the first or second aspect.

  According to a fourth aspect of the present invention, in the surface light emitting device according to the third aspect, the surface light emitting device is fabricated on a GaAs substrate inclined from the (001) plane direction.

  According to a fifth aspect of the present invention, in the surface light emitting device according to the third or fourth aspect, the surface light emitting device is a surface emitting laser device.

  According to a sixth aspect of the present invention, in the surface light emitting device according to the third or fourth aspect, the surface light emitting device is a resonator resonance type surface light emitting diode device.

  The invention described in claim 7 is a surface-emitting monolithic array characterized by being formed by the surface-emitting element described in claim 5 or 6.

  The invention described in claim 8 is an electrophotographic system using the surface light emitting device according to claim 5 or the surface emitting monolithic array according to claim 7.

  The invention described in claim 9 is an optical communication system characterized by using the surface light emitting device according to claim 5 or claim 6 or the surface emitting monolithic array according to claim 7.

  The invention described in claim 10 is an optical interconnection system characterized by using the surface light emitting device according to claim 5 or claim 6 or the surface emitting monolithic array according to claim 7.

  According to the first aspect of the present invention, the high refractive index layer is composed of an AlGaInP layer, the low refractive index layer is composed of an AlGaAs layer, and the two types of layers include a p-type semiconductor distributed Bragg reflection. In the vessel, at least the AlGaInP layer of the two types of layers uses Mg as the p-type impurity element, so that the diffusion of the impurity element can be prevented, the electric resistance is lower (low resistance), and the absorption loss A p-type semiconductor distributed Bragg reflector having a small size and high long-term reliability can be obtained.

Further, according to the invention described in claim 2, the high-refractive-index layer formed of the (Al _x2 Ga _1-x2 ) _y2 In _1-y2 P layer and the low-refractive-index layer formed of the Al _x1 Ga _1-x1 As layer In the p-type semiconductor distributed Bragg reflector in which the two types of layers contain a p-type impurity element, the reflection wavelength of the p-type semiconductor distributed Bragg reflector is shorter than 635 nm, and the Al _x1 Ga _1- The composition of the _x1 As layer is in the range of 0.95 ≦ x1 ≦ 1, and the (Al _x2 Ga _1-x2 ) _y2 In _1-y2 P layer is lattice-matched to the GaAs substrate, and the composition is x2 ≧ 0. In the range of 35, 0 <y2 <1, it is possible to obtain a p-type semiconductor distributed Bragg reflector that has extremely low electrical resistance and excellent reflection characteristics (high reflectivity) in a wavelength region shorter than the 635 nm band. Can do.

  According to the invention described in claim 3, since the surface light emitting device is characterized by comprising the p-type semiconductor distributed Bragg reflector according to claim 1 or 2, particularly from the 635 nm band. In the short wavelength region, a surface light emitting device capable of high output operation with low driving voltage can be provided.

  According to a fourth aspect of the present invention, in the surface light emitting device according to the third aspect, the surface light emitting device is fabricated on a GaAs substrate inclined from the (001) plane direction. Occurrence is reduced, crystal growth can be performed with high quality (crystallinity is improved), and a surface light emitting device with high yield in the wafer surface and high reliability can be obtained.

  According to a fifth aspect of the present invention, in the surface light emitting device according to the third or fourth aspect, since the surface light emitting device is a surface emitting laser device, it is driven particularly in a shorter wavelength region than the 635 nm band. It is possible to provide a surface emitting laser element having a low voltage and capable of high output operation.

  According to a sixth aspect of the present invention, in the surface light emitting device according to the third or fourth aspect, the surface light emitting device is a resonator resonance type surface light emitting diode device, and therefore has a shorter wavelength than the 635 nm band. In the region, a resonator resonance type surface light emitting diode element that has a low driving voltage and is capable of high output operation can be obtained.

  According to the invention described in claim 7, since the surface emitting monolithic array is characterized by being formed by the surface light emitting element according to claim 5 or 6, particularly in a shorter wavelength region than the 635 nm band. The surface emitting monolithic array can be provided with a low driving voltage and capable of high output operation.

  Further, according to the invention described in claim 8, since the electrophotographic system is characterized by using the surface light emitting device according to claim 5 or the surface light emitting monolithic array according to claim 7, the reliability is high. A high-definition electrophotographic system can be obtained.

  According to the invention described in claim 9, since the optical communication system is characterized by using the surface light emitting device according to claim 5 or claim 6 or the surface emitting monolithic array according to claim 7, A highly reliable optical communication system can be obtained.

According to a tenth aspect of the present invention, an optical interconnection system using the surface light emitting device according to the fifth or sixth aspect or the surface light emitting monolithic array according to the seventh aspect is used. A highly reliable optical interconnection system can be obtained.

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

(First form)
The first embodiment of the present invention is a p-type semiconductor distributed Bragg reflector in which the high refractive index layer is composed of an AlGaInP layer, the low refractive index layer is composed of an AlGaAs layer, and the two layers contain a p-type impurity element. The p-type impurity element in at least the AlGaInP layer of the two types is Mg.

  In the first embodiment, in the p-type semiconductor distributed Bragg reflector in which the high refractive index layer is composed of an AlGaInP layer, the low refractive index layer is composed of an AlGaAs layer, and the two types of layers include a p-type impurity element. Since at least the AlGaInP layer of the two types of layers has Mg as the p-type impurity element, diffusion of the impurity element can be prevented, the electric resistance is smaller (low resistance), the absorption loss is small, and A p-type semiconductor distributed Bragg reflector with high long-term reliability can be obtained.

  This first embodiment will be described in more detail below.

  Among mixed crystal semiconductor crystal growth methods, the MOCVD method is a growth method suitable for mass production, which can obtain a relatively large growth rate and is excellent in mass productivity such as throughput. Conventionally, Zn has been widely used as a p-type impurity element in AlGaInP mixed crystal growth using the MOCVD method as a growth method. However, Zn is very easy to diffuse, and there is a problem that it diffuses due to heat during crystal growth. In general, the diffusion rate varies depending on the type and composition of the semiconductor material. In particular, in the case of an impurity element having a high diffusion rate, segregation occurs at the semiconductor interface of a different type and composition, or in a semiconductor layer having a high diffusion rate. There is a problem in that the impurity element concentration of the metal is lowered.

  In the semiconductor heterostructure, the band edge energy of the valence band depends on the doping concentration of the impurity element, and in the thermal equilibrium state, the energy of the band edge is determined so that the Fermi level is equal in all materials. That is, even a material having the same valence band energy causes a difference in valence band energy due to a difference in doping concentration of the impurity element, which prevents carrier conduction.

  Further, in a light emitting device (for example, a surface emitting laser device or a resonator resonant LED) using a distributed Bragg reflector as a resonator mirror, the p-type impurity element Zn diffuses to the active layer during the operation of the device and emits light. There are problems with long-term reliability, such as reducing efficiency.

  In the distributed Bragg reflector, when the light corresponding to the reflection wavelength is incident and reflected, the heterointerface position corresponds to the nodes and antinodes of the standing wave of the electric field, and the impurity element segregates at the heterointerface. If this happens, light absorption by free carriers occurs at the position of the belly, resulting in a problem that the reflectance is lowered.

However, Mg has a smaller diffusion coefficient than Zn and can keep the influence of diffusion small. Therefore, when Mg is used as the p-type impurity element, the diffusion of the impurity element can be prevented, the above-described problems can be solved, and a semiconductor distributed Bragg reflector with low resistance and low absorption loss can be obtained. Here, Cp ₂ Mg or the like can be used as a Mg doping material in the MOCVD method. Also, C (carbon) can be used as the p-type impurity element of the AlGaAs layer. Carbon can be doped with CBr ₄ or the like as a doping material, or can be auto-doped without using a doping material by adjusting growth conditions such as the V / III ratio and temperature.

  Thus, in the first embodiment of the present invention, in order to obtain a highly reliable distributed Bragg reflector using AlGaInP as the high refractive index layer material and AlGaAs as the low refractive index material, the p-type impurity element of the AlGaInP material is used. Mg is used.

(Second form)
A second aspect of the present invention is composed of a high refractive index layer formed of an (Al _x2 Ga _1-x2 ) _y2 In _1-y2 P layer and a low refractive index layer formed of an Al _x1 Ga _1-x1 As layer, In a p-type semiconductor distributed Bragg reflector in which two types of layers contain a p-type impurity element, the reflection wavelength of the p-type semiconductor distributed Bragg reflector is shorter than 635 nm, and the Al _x1 Ga _1-x1 As layer In the range of 0.95 ≦ x1 ≦ 1, and the (Al _x2 Ga _1-x2 ) _y2 In _1-y2 P layer is lattice-matched to the GaAs substrate, and the composition is x2 ≧ 0.35, 0 It is characterized by being in a range of <y2 <1.

In the second embodiment, the layer is composed of a high refractive index layer made of (Al _x2 Ga _1-x2 ) _y2 In _1-y2 P layer and a low refractive index layer made of Al _x1 Ga _1-x1 As layer. In the p-type semiconductor distributed Bragg reflector including the p-type impurity element, the reflection wavelength of the p-type semiconductor distributed Bragg reflector is shorter than 635 nm, and the composition of the Al _x1 Ga _1-x1 As layer a range of 0.95 ≦ x1 ≦ 1, and the _{(Al x2 Ga 1-x2)} y2 in 1-y2 P layer is lattice matched to GaAs substrate, composition x2 ≧ 0.35,0 <y2 Since it is in the range of <1, it is possible to obtain a p-type semiconductor distributed Bragg reflector having extremely low electrical resistance and excellent reflection characteristics (high reflectivity) in a wavelength region shorter than the 635 nm band.

  This second embodiment will be described in more detail below.

_1, the Al _{x Ga 1-x} As mixed crystal material and lattice-matched to GaAs substrate _{(Al x2 Ga 1-x2)} y 2 In 1-y2 P mixed crystal band edge energy of the conduction band and the valence band of FIG. The band energy of the AlGaInP mixed crystal is described in, for example, the document “Appl. Phys. Lett. Vol. 50, No. 14, 1987, pp. 906”.

  In the AlGaInP mixed crystal, lattice matching with the GaAs substrate is obtained in a composition in which the ratio y of Al to Ga in the group III element is about 0.51. In addition, AlGaAs mixed crystals can be crystal-grown substantially lattice-matched with a GaAs substrate regardless of the Al composition. Therefore, all the mixed crystal materials in the range shown in the figure have a composition capable of crystal growth on the GaAs substrate. In the following description, it is assumed that the composition of AlGaInP is a composition (y2 = 0.51) that lattice matches with GaAs.

  Here, as can be seen from FIG. 1, in each mixed crystal, the energy in the valence band tends to gradually decrease as the Al composition increases, and in general, the AlGaInP mixed crystal material has a higher valence electron. Low band energy. Further, when the valence band energies of AlGaAs having a large Al composition and AlGaInP having a small Al composition are compared, it can be seen that they are approximately the same.

  FIG. 2 is a graph showing the refractive index of each mixed crystal at a wavelength of 635 nm with respect to the Al composition. The refractive index is shown for a composition range that is sufficiently transparent with respect to the wavelength of 635 nm.

In FIG. 2, the composition of AlGaAs is shown for a composition having an Al composition x larger than that of Al _0.67 Ga _0.33 As. Specifically, the photon energy at a wavelength of 635 nm is 1.952 eV, and the composition has a larger band gap energy by about 0.09 eV.

Further, the composition of AlGaInP is shown for a composition having an Al composition x larger than (Al _0.41 Ga _0.59 ) y ₂ In ₁ -y ₂ P. This composition is a composition having a large band gap energy of about 0.2 eV with respect to the photon energy. Here, the AlGaInP mixed crystal having the above composition is a direct transition, and light absorption is likely to occur as compared with an indirect transition type semiconductor. Therefore, a composition having a band gap energy sufficiently larger than the photon energy is selected. Thus, the loss due to absorption can be reduced by using a composition having a slightly larger band gap energy than that of the indirect transition semiconductor.

  As qualitatively understood from FIGS. 1 and 2, by using an AlGaAs mixed crystal for the low refractive index layer and an AlGaInP mixed crystal for the high refractive index layer as in the prior art, an AlGaAs mixed crystal or an AlGaInP mixed crystal is used. It is possible to obtain a distributed Bragg reflector with a large difference in refractive index and a small difference in valence band energy compared to the case where only this is configured.

In the prior art, the reflection wavelength is set to the above 650 nm, and (Al _0.27 Ga) _0.52 In _0.48 P and Al _0.9 Ga ₀ with respect to the reflection wavelength 650 nm in order to obtain a large refractive index difference. _.1 As a combination of As and a distributed Bragg reflector, the inventors of the present application pay attention to the refractive index difference of the two mixed crystals, and select a material as a combination that can take a large difference, and the electric resistance ( The valence band energy difference) has not been studied. Actually, the valence band energy difference between these two mixed crystals is not zero. In order to obtain a distributed Bragg reflector with excellent electrical and optical properties, further detailed examination is required.

  Therefore, the inventors of the present application have studied the band edge energy of the AlGaInP mixed crystal and AlGaAs mixed crystal, the wavelength band of the distributed Bragg reflector, and the like, and set the wavelength of the distributed Bragg reflector to a wavelength region shorter than 635 nm. As a result, the inventors have found a wavelength band and a composition range in which a distributed Bragg reflector having excellent characteristics as compared with the conventional one can be obtained.

  Tables 1 and 2 show the composition of AlGaInP that is sufficiently transparent to each wavelength and the valence band energy thereof. (The standard of the valence band energy is shown based on the conduction band energy of GaAs as shown in FIG. 1.)

  As described above, it is desirable to use a composition having a band gap energy sufficiently larger than the photon energy (Ep) in order to reduce the light absorption loss in the composition that causes direct transition. As a guideline, it is desirable to use a composition having a large band gap energy of about 0.15 eV to 0.2 eV. Tables 1 and 2 show compositions in which 0.15 eV and 0.2 eV band gap energy are larger than the photon energy, respectively, as an example.

  Table 3 shows the band gap energy of the AlAs layer, which is a low refractive index layer, and its valence band energy.

The AlGaAs mixed crystal used as the low refractive index layer is preferably AlAs having the smallest refractive index. However, in the selective oxidation process for forming a current confinement structure in consideration of application to a reflection mirror of a surface emitting laser, etc. In order to prevent oxidation of the AlGaAs layer other than the constriction layer, it is necessary to contain a slight amount of Ga in the composition. In the long wavelength band, a mixed crystal having a relatively large Ga composition of about 0.1 may be used. However, in the short wavelength band where it is difficult to obtain a large refractive index difference, an Al composition of 0.95 or more is practically used. It is desirable to use Here, the valence band energies of Al _0.95 Ga _0.05 As and AlAs are approximately −1.84 and −1.86 [eV], respectively, as shown in Table 3. The band gap energy of Al _0.95 Ga _0.05 As is 2.165 eV, which is larger than the photon energy of 2.0325 eV at a wavelength of 610 nm and is transparent.

Next, when attention is paid to the valence band energy of AlGaInP mixed crystal, the valence band energy is equal to -1.84eV of _{Al 0.95 Ga 0.05 As (Al x2} Ga 1-x2) y 2 In 1- _y2 P of Al composition: x2 is 0.37. In addition, including a composition in which the valence band discontinuity with Al _0.95 Ga _0.05 As is about 0.01 eV, the Al composition 0.34 is regarded as an acceptable composition on the low Al composition side. Can do.

  Similarly, Al composition equal to AlAs valence band energy minus 1.862 eV: x is 0.44. Similarly, if the band discontinuity difference up to 0.01 eV is included, the Al composition becomes 0.48 higher. It can be seen as an allowable value on the Al composition side.

In other words, by selecting the Al composition of the AlGaInP mixed crystal in the range of 0.34 to 0.48, the valence band is obtained for the AlGaAs mixed crystal having the composition of Al _0.95 Ga _0.05 As to AlAs. It can be seen that there are combinations in which the energy difference is 0 or the difference is 0.01 eV or less.

  Here, looking again at Table 1, it can be seen that when the transparent composition is Ep + 0.2 eV, 635 nm is included in the Al composition range 0.34 to 0.48. In Table 2, when the transparent composition is Ep + 0.15 eV, it can be seen that there are combinations that satisfy the above conditions in the 610 nm to 630 nm band.

  As described above, in the wavelength band shorter than 635 nm, the Al composition of the AlGaAs mixed crystal is set to 0.95 or more, and the Al composition of the AlGaInP mixed crystal is set to a range of approximately 0.35 or more. By selecting, a distributed Bragg reflector having a large refractive index difference (high reflectivity) and a small electric resistance (zero or very small valence band discontinuity) in a transparent range composition is obtained. I can do things.

  Thus, in the second embodiment of the present invention, the reflection wavelength is shorter than 635 nm, and the composition of the AlGaAs mixed crystal used for the low refractive index layer and the AlGaInP mixed crystal used for the high refractive index layer is set to a specific composition. By limiting, it is possible to obtain a p-type semiconductor distributed Bragg reflector having high reflectance and low electrical resistance.

(Third form)
According to a third aspect of the present invention, there is provided a surface light emitting device including the p-type semiconductor distributed Bragg reflector according to the first or second aspect.

  In the third embodiment, since the surface light emitting device includes the p-type semiconductor distributed Bragg reflector according to the first or second embodiment, the driving is performed particularly in a wavelength region shorter than the 635 nm band. It is possible to provide a surface light emitting element that is low in voltage and capable of high output operation.

  Thus, in the third embodiment of the present invention, a surface emitting device (surface emitting laser (VCSEL) device or resonator resonant light emitting diode (RCLED)) having excellent characteristics in a wavelength band shorter than 635 nm is obtained. Therefore, the above distributed Bragg reflector is used as a resonator mirror.

(4th form)
According to a fourth aspect of the present invention, in the surface light emitting device according to the third aspect, the surface light emitting device is fabricated on a GaAs substrate inclined from the (001) plane direction.

  That is, in the fourth embodiment, the surface light emitting element of the third embodiment is formed on a GaAs substrate inclined from the (001) plane orientation.

  In the fourth embodiment, in the surface light emitting device of the third embodiment, since the surface light emitting device is fabricated on a GaAs substrate inclined from the (001) plane direction, occurrence of hill-shaped defects is reduced, Crystal growth can be performed with high quality (crystallinity is improved), and a surface light emitting device with high yield in the wafer surface and high reliability can be obtained.

  The fourth embodiment will be described in detail below.

  It is known that (Al) GaInP mixed crystals are prone to occurrence of hill-like defects when crystal growth is performed by metal organic chemical vapor deposition (MOCVD) or the like. Hill-like defects cause a decrease in device yield and reliability. Such a problem is remarkable when crystal growth is performed on a GaAs substrate having a (001) plane orientation, and there is a problem that the yield of the device is remarkably reduced due to the occurrence of a hill-like defect.

  These problems can be improved by using a substrate whose plane orientation is inclined from the (001) plane to the (111) A plane direction or the (111) B plane direction. In this way, by using an inclined substrate, it is possible to reduce the occurrence of hill-shaped defects and to perform crystal growth with high quality (improves crystallinity), and the yield in the wafer surface is high and reliable. Can be obtained.

(5th form)
According to a fifth aspect of the present invention, in the surface light emitting device of the third or fourth aspect, the surface light emitting device is a surface emitting laser device.

  In the fifth embodiment, in the surface light emitting device of the third or fourth embodiment, since the surface light emitting device is a surface emitting laser device, the driving voltage is low and the output is particularly high in a wavelength region shorter than the 635 nm band. A surface-emitting laser element capable of operation can be provided.

  That is, in the fifth embodiment, the p-type semiconductor distributed Bragg reflector of the first or second embodiment is used as a reflecting mirror of the surface emitting laser element. In particular, in the semiconductor distributed Bragg reflector of the second embodiment, it is possible to obtain a p-type semiconductor distributed Bragg reflector that has very good optical (reflection characteristics) and electrical resistance on the shorter wavelength side than the 635 nm band. It is possible, and the characteristics of the visible surface emitting laser element at a wavelength shorter than the 635 nm band can be greatly improved.

  The visible surface emitting laser element uses an AlGaInP material system as an active layer material. However, since the conduction band discontinuity between the active layer and the barrier layer is small in this material, the overflow of injected electrons is large. In addition, it is easily affected by heat generated during laser operation. That is, there is a problem that oscillation is hindered by a temperature rise due to energization, and even when oscillation occurs, oscillation is easily stopped if the injection current is increased. This tendency becomes more prominent as the oscillation wavelength becomes shorter (as the conduction band discontinuity between the active layer and the barrier layer becomes smaller).

  On the other hand, since the p-type semiconductor distributed Bragg reflector according to the second embodiment has a low resistance, heat generation due to energization is small and oscillation can be easily obtained. Further, it is possible to stably oscillate up to a high injection flow area.

  As described above, the surface-emitting laser element using the p-type semiconductor distributed Bragg reflector of the present invention (in the visible band) has a low driving voltage and can perform a high output operation particularly in a wavelength region shorter than the 635 nm band. Become.

(Sixth form)
According to a sixth aspect of the present invention, in the surface light emitting element of the third or fourth aspect, the surface light emitting element is a resonator resonance type surface light emitting diode element.

  In the sixth embodiment, in the surface light emitting device of the third or fourth embodiment, since the surface light emitting device is a resonator resonance type surface light emitting diode device, the driving voltage is particularly reduced in a wavelength region shorter than the 635 nm band. A resonator-resonant surface-emitting diode element that is low and capable of high output operation can be obtained.

  That is, in the sixth embodiment, the p-type semiconductor distributed Bragg reflector of the first or second embodiment is used as a reflector of a resonator resonant surface light emitting diode element having an emission wavelength shorter than 635 nm.

  By adopting such a configuration, similarly to the fifth embodiment, it is possible to obtain a resonator-resonant surface light emitting diode element that has a low driving voltage and is capable of high output operation, particularly in a wavelength region shorter than the 635 nm band. it can.

(7th form)
A seventh aspect of the present invention is a surface-emitting monolithic array characterized by being formed by the surface-emitting elements of the fifth or sixth aspects.

  In the seventh embodiment, since the surface emitting monolithic array is characterized by being formed by the surface light emitting element of the fifth or sixth embodiment, the driving voltage is low particularly in a shorter wavelength region than the 635 nm band. A surface-emitting monolithic array capable of high output operation can be provided.

  That is, in the seventh embodiment, a surface emitting monolithic array is configured using the surface emitting elements of the fifth or sixth embodiment. The surface emitting element (surface emitting laser element or resonator resonance type surface emitting diode element) according to the present invention has a low driving voltage and is capable of high output operation. Therefore, a surface-emitting monolithic array configured using the surface-emitting device (surface-emitting laser device or resonator resonant surface-emitting diode device) of the present invention also has a low driving voltage and can operate at a high output.

  Thus, in the seventh embodiment, a surface emitting monolithic array (surface emitting laser array, resonator resonance type surface emitting diode array) that has a low driving voltage and can perform a high output operation can be obtained.

(Eighth form)
An eighth aspect of the present invention is an electrophotographic system characterized by using the surface light emitting element of the fifth form or the surface light emitting monolithic array of the seventh form.

  In the eighth embodiment, since the electrophotographic system is characterized by using the surface light-emitting element of the fifth embodiment or the surface-emitting monolithic array of the seventh embodiment, highly reliable and high-definition electronic You can get a photo system.

  That is, in the eighth embodiment, electrophotography using the surface emitting device (surface emitting laser device) of the fifth embodiment or the surface emitting monolithic array (for example, surface emitting laser array) of the seventh embodiment as a writing light source. The system is configured.

  The surface emitting device of the fifth form (surface emitting laser element) or the surface emitting monolithic array of the seventh form (for example, a surface emitting laser array) has a low drive driving voltage and low power consumption, and obtains a higher output. Things are possible. In particular, when a surface-emitting monolithic array is used as a light source, the individual elements constituting the surface-emitting monolithic array have high positional accuracy in the array, so that multiple beams can be easily reproduced with the same lens. Therefore, it is possible to obtain a low-cost electrophotographic system. In particular, when a surface emitting laser element in the visible band (red band) is used as a writing light source, since the wavelength is short, the beam spot diameter converged on the photosensitive drum can be reduced, and high definition is achieved. An electrophotographic system can be obtained.

(9th form)
A ninth aspect of the present invention is an optical communication system characterized by using the surface light emitting element of the fifth or sixth form or the surface light emitting monolithic array of the seventh form.

  In the ninth embodiment, since the optical communication system is characterized by using the surface light emitting element of the fifth or sixth embodiment or the surface emitting monolithic array of the seventh embodiment, highly reliable optical communication. You can get a system.

  That is, in the ninth embodiment, an optical communication system is configured using the surface light emitting element of the fifth or sixth embodiment or the surface emitting monolithic array of the seventh embodiment as a light source.

  The surface light emitting device of the fifth or sixth form has a low operating voltage and can perform a high output operation. Therefore, since a large signal strength can be obtained, a highly reliable communication system with high speed and few communication errors can be obtained. Further, since a higher output can be obtained than in the conventional case, long-distance communication is possible. Therefore, a highly reliable optical communication system can be obtained by using these as a light source. In particular, a visible band (red band) surface emitting laser element and a resonator resonance type surface emitting diode element are suitable as a light source for a communication system using a plastic fiber (POF). A highly reliable communication system can be obtained by using the resonator resonance type surface light emitting diode element as a light source.

(10th form)
A tenth aspect of the present invention is an optical interconnection system characterized by using the surface light emitting element of the fifth or sixth form or the surface light emitting monolithic array of the seventh form.

  In the tenth embodiment, since the optical interconnection system is characterized by using the surface light emitting element of the fifth or sixth embodiment or the surface emitting monolithic array of the seventh embodiment, a highly reliable light You can get an interconnection system.

  That is, in the tenth embodiment, an optical interconnection system is configured by using the surface light emitting element of the fifth or sixth embodiment or the surface emitting monolithic array of the seventh embodiment as a light source.

  The surface light emitting device of the fifth or sixth form has a low operating voltage and can perform a high output operation. Therefore, since a large signal strength can be obtained, a highly reliable communication interconnection system with high speed and few communication errors can be obtained. In addition, since high output can be obtained compared to the conventional case, optical transmission over a long distance is possible. Therefore, by using these as light sources, a highly reliable optical interconnection system can be obtained. In particular, a visible band (red band) surface emitting laser element and a resonator resonance type surface emitting diode element are suitable as a light source of an optical interconnection system using a plastic fiber (POF), and the visible band surface emitting laser according to the present invention. A highly reliable optical interconnection system can be obtained by using an element and a resonator resonant surface light emitting diode element as a light source.

  FIG. 3 is a diagram illustrating the surface emitting laser element according to the first embodiment. The surface emitting laser element of FIG. 3 is a 635 nm band surface emitting laser element having a GaInP / AlGaInP multiple quantum well structure as an active layer.

  In the following, the structure of the surface emitting laser element shown in FIG.

In the production of the surface emitting laser element shown in FIG. 3, crystal growth is performed by metal organic chemical vapor deposition (MOCVD), and trimethylaluminum (TMA), trimethylgallium (TMG), and trimethylindium (TMI) are used as group III materials. And phosphine (PH ₃ ) gas and arsine (AsH ₃ ) gas are used as the group V raw material. Further, carbon tetrabromide (CBr ₄ ) is used as a p-type impurity element doping material for the AlGaAs layer, and cyclopentadiphenyl magnesium (Cp ₂ Mg) is used as a p-type impurity element doping material for the AlGaInP layer. . Further, hydrogen selenide (H ₂ Se) is used as a doping material for the n-type impurity element.

Specifically, the element of FIG. 3 includes an n-GaAs buffer layer 102, n-Al _0.95 Ga _0.05 As / (Al _0.41 Ga _0.59 ) _0.5 on an n-GaAs substrate 101. 60.5 period n-Al _0.95 Ga _0.05 As / (Al _0.41 Ga _0.59 ) _0.5 In _0.5 P lower semiconductor distribution with a pair of In _0.5 P as one period Bragg reflector 103, non-doped (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P resonator spacer 104, GaInP / AlGaInP multiple quantum well active layer 105, non-doped (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P resonator spacer 106, 35 periods of p-Al _0.59 Ga _0.05 As / (Al _0.41 Ga _0.59 ) _0.5 In _0.5 P upper semiconductor distribution Bragg Reflection Crystal growth of the vessel 107 is performed. Here, a p-AlAs selective oxide layer 108 is provided in the middle of the upper semiconductor distributed Bragg reflector 107. A GaAs contact layer (not shown) is provided on the outermost surface of the element.

  Here, as the GaAs substrate 101, an inclined substrate whose plane orientation is inclined by 15 ° from the (001) plane orientation to the (111) A direction is used. By using such a substrate 101, it was possible to obtain good surface properties without occurrence of hill-like defects.

  In addition, the device of this example can be obtained by sufficiently optimizing the growth conditions at the interface for switching the raw material atmosphere from the semiconductor layer having As as a group V element to the semiconductor layer having P as a group V element. It was possible to obtain excellent surface properties (mirror surface).

  Here, the thickness of each semiconductor layer constituting the semiconductor distributed Bragg reflector is λ / 4n (n with respect to the laser oscillation wavelength (λ = 635 nm) so as to satisfy the multiple reflection phase condition of the semiconductor distributed Bragg reflector. Is the thickness of the refractive index of each semiconductor layer with respect to the laser oscillation wavelength, which is the same in the following examples).

  FIG. 4 is a diagram showing a configuration of a part of the p-type semiconductor distributed Bragg reflector 107 corresponding to the light emitting side of the surface emitting laser element of FIG. As shown in FIG. 4, the p-type semiconductor distributed Bragg reflector 107 is configured by alternately laminating low refractive index layers made of AlGaAs mixed crystals and high refractive index layers made of AlGaInP mixed crystals.

In this example, (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P resonator spacer 104, GaInP / AlGaInP multiple quantum well active layer 105, non-doped (Al _0.5 Ga _0.5 The resonance region composed of the _0.5 In _0.5 P resonator spacer 106 has a phase change of light of 2π in these semiconductor layers, and forms a one-wavelength resonator structure. In order to obtain a high stimulated emission probability, the GaInP / AlGaInP multiple quantum well active layer 105 is provided at a position corresponding to the antinode of the standing wave of the oscillation light in the center of the resonator.

  As described above, in this embodiment, a semiconductor distributed Bragg reflector in which an AlGaInP mixed crystal material and an AlGaAs mixed crystal material are combined is used.

  Next, a circular resist pattern having a diameter of 30 μm is formed in the central portion of the surface emitting laser element shown in FIG. 3 using a known photolithography technique, and then n is applied from the surface GaAs contact layer using a known dry etching technique. Etching of each layer up to the side distributed Bragg reflector 103 is performed to form a mesa. Next, the current confinement layer is formed by oxidizing the p-AlAs selective oxidation layer 108 from the mesa side wall in a heated steam atmosphere. In FIG. 3, the region oxidized in the p-AlAs selective oxide layer 108 is shown in black. Here, the diameter of the non-oxidized region at the center of the element is 3 μm.

Next, a SiO ₂ layer 109 is formed on the entire surface of the wafer by using a known chemical vapor deposition method (CVD method), and is then aligned with the etching removal portion to form a light emitting portion and its surrounding SiO _2. The layer 109 is removed. Next, spin coating of the insulating resin 110 is performed, and the insulating resin on the top surface of the mesa is removed as shown in FIG. Next, a circular resist pattern having a diameter of 5 μm is formed in a region to be a light emitting part, and after depositing a p-side electrode material, the electrode material of the light emitting part is removed by lift-off to form a p-side electrode 111. ing. Next, after polishing the back surface of the n-GaAs substrate 101, an n-side electrode 112 is formed on the back surface of the substrate 101 by vapor deposition, and ohmic conduction between both electrodes is achieved by annealing.

  In the surface emitting laser element of this example, the p-type semiconductor distributed Bragg reflector is configured using an AlGaAs mixed crystal material and an AlGaInP mixed crystal material, and in particular, the composition of the p-type semiconductor distributed Bragg reflector is the above at a wavelength of 635 nm. In this way, high reflectivity and low resistance (small valence band discontinuity) can be realized at the same time.

  As described above, the surface emitting laser element of Example 1 including the p-type semiconductor distributed Bragg reflector according to the present invention has a lower driving voltage and an oscillation threshold current than those of the conventional element, and can perform a higher output operation. there were.

  In the first embodiment, an oxide constriction structure by selective oxidation is used as the current confinement structure. In addition to this, a high resistance layer by (hydrogen) ion implantation is used as the current confinement structure as in the second embodiment. You can also do things.

  FIG. 5 is a view showing a surface emitting laser element of Example 2. In the surface emitting laser element of Example 2, a high resistance layer provided by hydrogen ion implantation is used as the current confinement structure. In other respects, the surface emitting laser element of Example 2 is a 635 nm band surface emitting laser element having a GaInP / AlGaInP multiple quantum well structure as an active layer, as in Example 1, and has the same crystal as in Example 1. Growth is performed by a growth method and means.

  Hereinafter, the structure of the surface emitting laser element of FIG. 5 will be described according to the manufacturing process.

Specifically, the surface emitting laser element of FIG. 5 includes an n-GaAs buffer layer 202, n-AlAs / (Al _0.41 Ga _0.59 ) _0.5 In _0.5 P on an n-GaAs substrate 201. N-AlAs / (Al _0.41 Ga _0.59 ) _0.5 In _0.5 P lower semiconductor distributed Bragg reflector 203 having a pair of 1 cycle, non-doped (Al _0.5 Ga _{0 .5) 0.5} In _0.5 P cavity spacer 204, GaInP / AlGaInP multiple quantum well active layer 205, an undoped _{(Al 0.5 Ga 0.5) 0.5 In} 0.5 P cavity spacer 206, Crystal growth of p-AlAs / (Al _0.41 Ga _0.59 ) _0.5 In _0.5 P upper semiconductor distributed Bragg reflector 207 with 35 periods is performed. Here, a GaAs contact layer (not shown) is provided on the outermost surface of the element.

Next, after forming a 5 μm circular resist pattern in a region to be a light emitting portion of the element using a known photolithography technique, hydrogen ions are implanted using a known ion implantation technique to obtain a high resistance region 208. Is provided. Next, after removing the resist, the SiO ₂ layer 209 is formed on the element over the entire surface by a known CVD technique is performed to remove the SiO ₂ layer 209 near the light emitting portion by photolithography and wet etching techniques . Next, as in Example 1, after forming the p-side electrode 210 and polishing the back surface of the substrate 201, the n-side electrode 211 was formed on the back surface of the substrate 201 and a thermal annealing treatment was performed. A surface emitting laser element was produced.

  In the surface emitting laser element of Example 2, as in Example 1, the p-type semiconductor distributed Bragg reflector is configured by using an AlGaAs mixed crystal material and an AlGaInP mixed crystal material. In particular, the p-type semiconductor distributed Bragg reflector is used. By selecting the above composition at a wavelength of 635 nm as described above, high reflectivity and low resistance (small valence band band discontinuity) could be realized simultaneously.

  Thus, the surface emitting laser element of Example 2 equipped with the p-type semiconductor distributed Bragg reflector of the present invention has a lower driving voltage and oscillation threshold current than the conventional element, and can operate at a higher output. there were.

  FIG. 6 is a view showing a resonator resonance type light emitting diode element of Example 3. FIG. The resonator resonant light-emitting diode element of Example 3 is a light-emitting diode element having a GaInP / AlGaInP multiple quantum well structure as an active layer and having an emission wavelength in the 610 nm band. The same crystal growth method as in Example 1 and Example 2 And growth is done by means.

  Hereinafter, the structure of the resonator resonance type light emitting diode element of FIG. 6 will be described according to the manufacturing process.

Specifically, the resonator resonant light-emitting diode element of FIG. 6 has an n-GaAs buffer layer 302, n-AlAs / (Al _0.55 Ga _0.45 ) _0.5 In ₀ on an n-GaAs substrate 301. _.5 P pair of 1 period, 60.5 periods of n-AlAs / (Al _0.55 Ga _0.45 ) _0.5 In _0.5 P lower semiconductor distributed Bragg reflector 303, non-doped (Al _{0. 7} Ga _{0.3) 0.5} In _0.5 P cavity spacer 304, GaInP / AlGaInP multiple quantum well active layer 305, undoped _{(Al 0.7 Ga 0.3) 0.5 In} 0.5 P resonator spacer _{306,5 p-AlAs / (Al 0.55} Ga 0.45) cycle 0.5 _{an in 0.5} P crystal growth of the upper semiconductor DBR 307 is performed. A GaAs contact layer (not shown) is provided on the outermost surface of the element.

Next, after forming a 5 μm circular resist pattern in a region to be a light emitting portion of the element using a known photolithography technique, hydrogen ions are implanted using a known ion implantation technique to obtain a high resistance region 308. Is provided. Next, after removing the resist, the SiO ₂ layer 309 is formed on the element over the entire surface by a known CVD technique is performed to remove the SiO ₂ layer 309 near the light emitting portion by photolithography and wet etching techniques . Next, in the same manner as in Example 1, after forming the p-side electrode 310 and polishing the back surface of the substrate 302, the n-side electrode 311 is formed on the back surface of the substrate 302 and a thermal annealing process is performed. A resonant light-emitting diode element was produced.

  In the resonator-resonant light emitting diode element of Example 3, as in Examples 1 and 2, the p-type semiconductor distributed Bragg reflector is configured using an AlGaAs mixed crystal material and an AlGaInP mixed crystal material. By selecting the composition of the p-type semiconductor distributed Bragg reflector as described above at a wavelength of 620 nm, high reflectivity and low resistance (small valence band discontinuity) can be realized simultaneously.

  As described above, the resonator-resonant light-emitting diode element of Example 3 has a lower driving voltage and can operate at a higher output than the conventional element.

  In each of the above embodiments, the MOCVD method has been described as an example of the crystal growth method, but other crystal growth methods such as a molecular beam crystal growth method (MBE method) may also be used. it can. In addition to the 635 nm band and the 610 nm band described above, the oscillation (light emission) wavelength can be applied to the visible band shorter than 635 nm. The element structure may be a structure other than that shown in each of the above-described embodiments.

  FIG. 7 is a view showing a surface emitting laser array of Example 4. That is, FIG. 7 shows a top view of a surface emitting monolithic laser array in which 4 × 4 surface emitting laser elements of the present invention are two-dimensionally integrated.

  In the example of FIG. 7, wirings are individually provided on the upper electrode in order to drive each element independently. Further, the surface emitting laser array of FIG. 7 is manufactured by the same procedure and method as the above-described embodiments, and individual elements constituting the surface emitting laser array are AlGaInP mixed crystals as a high refractive index layer. A semiconductor distributed Bragg reflector is formed using a material and using an AlGaAs mixed crystal material as a low refractive index layer.

  As a result, each element has a low resistance and a low driving voltage, so that the power consumption required to obtain the same output as the conventional one is low, and the output saturation point due to heat generation is also high.

  As described above, a surface emitting laser array capable of high output operation was obtained.

  FIG. 8 is a diagram showing an electrophotographic system according to the fifth embodiment. The electrophotographic system of FIG. 8 includes a photosensitive drum, an optical scanning system (scanning convergence optical system), a writing light source, and a synchronization control circuit (synchronization control unit). A surface emitting laser element or a surface emitting laser array is used.

  The electrophotographic system of FIG. 8 is controlled by a synchronous control circuit, and light from a writing light source (surface emitting laser element or surface emitting laser array of the present invention) is photosensitized by a scanning converging optical system including a polygon mirror and a lens converging system. It is condensed on the drum to form a latent image.

  Since the surface emitting laser element or the surface emitting laser array of the present invention is capable of high output operation, high speed writing is possible and a high speed electrophotographic system can be obtained.

  A red surface emitting laser element using an AlGaInP-based material as an active layer material can oscillate in the visible band of 635 nm or less. Therefore, it is suitable as a writing light source for high-definition electrophotography. However, AlGaInP-based materials are very susceptible to temperature changes, and output saturation, oscillation stoppage, and the like are problematic due to temperature rise caused by element heat generation. However, the red surface emitting laser element to which the present invention is applied includes a low-resistance semiconductor distributed Bragg reflector in which the low refractive index layer is made of an AlGaAs mixed crystal material and the high refractive index layer is made of an AlGaInP mixed crystal material. Therefore, the heat generation of the element is reduced, and a high output operation can be obtained.

  As described above, the surface emitting laser element or the surface emitting laser array of the present invention is suitable as a writing light source for an electrophotographic system.

  FIG. 9 illustrates an optical interconnection system according to the sixth embodiment. The interconnection system of FIG. 9 is configured such that the devices 1 and 2 are connected using an optical fiber array.

  The device 1 on the transmission side is provided with a one-dimensional array module using a surface emitting laser element or a resonator resonance type light emitting diode element according to the present invention, and a drive circuit thereof. The device 2 on the receiving side is provided with a photodiode array module and a signal detection circuit. In Example 6, a surface emitting laser element or a light emitting diode element is used in the visible band (red band), and a plastic fiber (POF) is suitable as an optical fiber in such a wavelength band. .

  In addition, the optical interconnection system of Example 6 uses an array of surface-emitting laser elements or resonator-resonant light-emitting diode elements according to the present invention, so that the drive voltage is low and high output operation is possible. Met. In addition, since a high output operation is possible, it was possible to construct a highly reliable interconnection system with few transmission errors.

  Although the parallel optical interconnection system has been described as an example in the sixth embodiment, a serial transmission system using a single element can also be configured. In addition to inter-device, it can also be applied to inter-board, inter-chip, and intra-chip interconnections.

In addition to the electrophotographic system, the optical communication system, and the optical interconnection system, the present invention can be used for a display system and the like.

In view showing a Al _x Ga _1-x As mixed crystal material and lattice-matched to GaAs substrate _{(Al x2 Ga 1-x2)} y 2 In 1-y2 P mixed crystal band edge energy of the conduction band and the valence band of is there. It is the figure which showed the refractive index of each mixed crystal in wavelength 635nm with respect to Al composition. 1 is a diagram illustrating a surface emitting laser element of Example 1. FIG. It is a figure which shows the structure of a part of p-type semiconductor distributed Bragg reflector 107 which hits the light emission side of the surface emitting laser element of FIG. 6 is a view showing a surface emitting laser element according to Example 2. FIG. 6 is a diagram showing a resonator resonance type light emitting diode element of Example 3. FIG. 6 is a diagram showing a surface emitting laser array of Example 4. FIG. 10 is a diagram illustrating an electrophotographic system of Example 5. FIG. It is a figure which shows the optical interconnection system of Example 6. FIG.

Explanation of symbols

101 n-GaAs substrate 102 n-GaAs buffer layer 103 lower semiconductor distributed Bragg reflector 104 resonator spacer 105 multiple quantum well active layer 106 resonator spacer 107 upper semiconductor distributed Bragg reflector 108 p-AlAs selective oxide layer 109 SiO ₂ layer 110 insulating resin 111 p-side electrode 112 n-side electrode 201 n-GaAs substrate 202 n-GaAs buffer layer 203 lower semiconductor distributed Bragg reflector 204 resonator spacer 205 multiple quantum well active layer 206 resonator spacer 207 upper semiconductor distributed Bragg reflection 208 High resistance region 209 SiO ₂ layer 210 p-side electrode 211 n-side electrode 301 n-GaAs substrate 302 n-GaAs buffer layer 303 Lower semiconductor distributed Bragg reflector 304 Resonator spacer -305 Multiple quantum well active layer 306 Resonator spacer 307 Upper semiconductor distributed Bragg reflector 308 High resistance region 309 SiO ₂ layer 310 p-side electrode 311 n-side electrode

Claims (10)

In the p-type semiconductor distributed Bragg reflector in which the high refractive index layer is composed of an AlGaInP layer, the low refractive index layer is composed of an AlGaAs layer, and the two types of layers include a p-type impurity element, A p-type semiconductor distributed Bragg reflector, wherein the p-type impurity element in at least the AlGaInP layer is Mg. _{(Al x2 Ga 1-x2)} y2 and the high refractive index layer by _{an In 1-y2} P _layer, is composed of a low refractive index layer by Al _{x1 Ga 1-x1} As layer, the two layers are p-type impurity element In the p-type semiconductor distributed Bragg reflector, the reflection wavelength of the p-type semiconductor distributed Bragg reflector is shorter than 635 nm, and the composition of the Al _x1 Ga _1-x1 As layer is 0.95 ≦ x1 ≦. 1 and the (Al _x2 Ga _1-x2 ) _y2 In _1-y2 P layer is lattice-matched to the GaAs substrate and has a composition of x2 ≧ 0.35 and 0 <y2 <1. A p-type semiconductor distributed Bragg reflector. A surface light emitting device comprising the p-type semiconductor distributed Bragg reflector according to claim 1. 4. The surface light emitting device according to claim 3, wherein the surface light emitting device is fabricated on a GaAs substrate inclined from the (001) plane direction. 5. The surface emitting device according to claim 3, wherein the surface emitting device is a surface emitting laser device. 5. The surface light emitting device according to claim 3, wherein the surface light emitting device is a resonator resonance type surface light emitting diode device. A surface-emitting monolithic array comprising the surface-emitting element according to claim 5. An electrophotographic system using the surface light emitting device according to claim 5 or the surface light emitting monolithic array according to claim 7. An optical communication system using the surface-emitting device according to claim 5 or the surface-emitting monolithic array according to claim 7. An optical interconnection system using the surface-emitting element according to claim 5 or claim 6 or the surface-emitting monolithic array according to claim 7.

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