JP2006253340A - Surface emission laser element, manufacturing method thereof, surface emission laser array, electrophotographic system, optical communication system, and optical interconnection system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reliable surface emission laser element of less leak current and high current constriction efficiency. <P>SOLUTION: A surface emission laser element comprises an active layer 105, a current constriction structure which comprises a current preventing part 116, and a conductor 115 to regulate a current injection region to the active layer 105, and a pair of distributed Bragg reflectors 103; 107, 111 provided to face each other across the active layer 105. The current preventing part 116 is formed of a multilayer structure including a plurality of hetero interfaces in which semiconductor layers different in gap energy are laminated alternately. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a surface emitting laser element, a manufacturing method thereof, a surface emitting laser array, an electrophotographic system, an optical communication system, and an optical interconnection system.

  Surface-emitting laser (surface-emitting semiconductor laser) elements are attracting attention as communication light sources for LANs and the like because they have a smaller active layer volume than low-end surface-emitting semiconductor laser elements, can operate at low threshold currents, and can be modulated at high speed. ing. In addition, the surface-emitting laser can be easily integrated in a two-dimensional array because the laser output can be taken out in the direction perpendicular to the substrate. Has been.

As a typical structure of a surface emitting laser element, for example, a surface emitting laser having a selective oxidation constriction type structure described in Non-Patent Document 1 (hereinafter referred to as a selective oxidation type surface emitting laser element) is known. . The selective oxidation surface emitting laser element is an insulating layer (Al) formed by oxidizing a semiconductor layer containing Al such as AlAs provided in the structure of a surface emitting laser element by crystal growth in high-temperature steam. _x O _y ). In this type of surface-emitting laser element, since the oxide of Al is a very good insulator, the injected carriers can be very efficiently confined to the conductive part that is not selectively oxidized at the center of the element. This provides a very low oscillation threshold of sub-milliamperes.

As another current confinement means (structure) in a surface emitting laser element, a structure in which current confinement is performed by a high resistance layer made of a semiconductor material is also known. For example, Patent Document 1 discloses a current confinement structure using a high-resistance semiconductor thin film layer as a current confinement layer (current blocking portion). For example, Patent Document 2 discloses an example in which a semiconductor layer having a larger band gap energy than a peripheral semiconductor layer is used as a current confinement structure, and a current confinement structure is formed so as to surround an active layer in a direction parallel to the substrate surface. It is shown.
Electronics Letters, Vol. 30, no. 24, pp. 2043-2044, 1994 JP 2004-179468 A JP-A-6-314855

A selective oxidation type surface emitting laser element as shown in Non-Patent Document 1 can confine injection carriers very efficiently by Al _x O _y which is a good insulator. However, since the refractive index of Al oxide is about 1.6, which is about half that of the semiconductor layer, very large transverse mode confinement occurs and single fundamental transverse mode oscillation can be obtained. There is a problem that is difficult. In many applications, such as fiber communications and electrophotographic system light sources, single fundamental transverse mode oscillation at high power is desired. In a selective oxidation type surface emitting laser element, the most commonly known method for obtaining a single fundamental transverse mode oscillation is to calculate a side or diameter of a non-oxidized region of a current confinement structure formed by a selective oxidation process. It is set to about 3 to 4 times the oscillation wavelength. Since the selectively oxidized region forms a low refractive index region with respect to the peripheral semiconductor layer, an actual refractive index waveguide structure is formed, and one side or diameter of the non-oxidized region is set to about 3 to 4 times the oscillation wavelength. The cut-off condition for the higher order transverse mode is satisfied. However, in actuality, the length or diameter of one side in the non-oxidized region at this time is as very small as 3 to several μm, and an increase in driving voltage (increased resistance) due to the constriction structure and the emission region Reduction of output due to reduction is a problem. The selective oxidation process is very sensitive to the film thickness, Al composition and oxidation temperature of the selective oxidation layer, and it is very difficult to obtain high uniformity and reproducibility in the wafer surface. This is a factor that reduces the yield of the element. In addition, strain stress is generated at the interface of the Al _x O _y layer formed by selective oxidation due to volume shrinkage due to the oxidation of the Al _x O _y layer, and the mesa structure may be broken in the subsequent process. Furthermore, the strain stress is considered to have an adverse effect on the reliability of the element when viewed over a long period of time.

On the other hand, in Patent Document 1 and Patent Document 2, by using a semiconductor process technology having relatively high controllability such as etching and photoengraving technology as a method for producing a current confinement structure, Improves reproducibility, uniformity, and reliability issues. Although not specifically mentioned in Patent Documents 1 and 2, the above-described problems related to optical confinement can be improved by forming a current confinement structure with a semiconductor layer. In practice, however, auto-doping and residual impurities are used in crystal growth methods useful for mass productivity (throughput) such as metal organic chemical vapor deposition (MOCVD) and device characteristics (reducing the resistance of distributed Bragg reflectors). As a result, there is a problem that it is difficult to obtain a high resistance semiconductor layer by sufficiently reducing the concentration of impurities such as Si and carbon in a semiconductor layer such as AlGaAs. Even if a semiconductor layer having a relatively high resistance and a large band gap energy is used, the band gap energy is _{equal to} the band gap energy of Al _x O _y which is a current blocking layer of the selective oxidation surface emitting laser element. Compared to this, it cannot be said that sufficient insulation is obtained. In particular, in a surface emitting laser element capable of obtaining an extremely low threshold current, even a slight leak current is considered to have a large effect on the threshold current value.

  The present invention provides a highly reliable surface-emitting laser device having a low leakage current and a high current confinement efficiency, a manufacturing method thereof, a surface-emitting laser array, an electrophotographic system, an optical communication system, and an optical interconnection system. It is an object.

  In order to achieve the above object, the invention according to claim 1 is characterized in that an active layer, a current confinement structure that defines a current injection region into the active layer, which includes a current blocking portion and a conduction portion, and sandwiches the active layer. In the surface emitting laser device including a pair of distributed Bragg reflectors provided opposite to each other, the current blocking unit has a multilayer structure including a plurality of heterointerfaces in which semiconductor layers having different band gap energies are alternately stacked. It is characterized by being formed.

  According to a second aspect of the present invention, there is provided the surface emitting laser element according to the first aspect, wherein the conducting portion has a band gap energy between semiconductor layers having different band gap energies forming the current blocking portion. It is characterized by being composed of layers.

  According to a third aspect of the present invention, in the surface-emitting laser device according to the first aspect, the conductive portion is a semiconductor having a small band gap energy among semiconductor layers having different band gap energies forming the current blocking portion. It is characterized by being composed of a semiconductor layer having a smaller band gap energy than the layer.

  According to a fourth aspect of the present invention, in the surface emitting laser element according to any one of the first to third aspects, the multilayer structure in which semiconductor layers having different band gap energies are alternately stacked A semiconductor layer having a relatively small band gap energy among the semiconductor layers having different band gap energies in the vicinity of the position corresponding to the node of the standing wave of light, and in the vicinity of the position corresponding to the antinode of the standing wave In addition, a semiconductor layer having a relatively large band gap energy among the semiconductor layers having different band gap energies is provided.

  According to a fifth aspect of the present invention, in the surface-emitting laser element according to any one of the first to fourth aspects, each semiconductor layer constituting the multilayer structure of the current blocking portion is formed of a non-doped semiconductor. It is characterized by being.

  According to a sixth aspect of the present invention, in the method for manufacturing a surface-emitting laser element according to any one of the first to fifth aspects, the conductive portion alternately includes semiconductor layers having different band gap energies. It is characterized by being formed by interdiffusion of group III elements into a multilayer structure including a plurality of stacked hetero interfaces.

  According to a seventh aspect of the invention, there is provided a surface emitting laser array comprising a plurality of the surface emitting laser elements according to any one of the first to fifth aspects. .

  The invention according to claim 8 is characterized in that the surface emitting laser element according to any one of claims 1 to 5 or the surface emitting laser array according to claim 7 is used as a light source. It is an electrophotographic system.

  The invention according to claim 9 is characterized in that the surface-emitting laser element according to any one of claims 1 to 5 or the surface-emitting laser array according to claim 7 is used as a light source. Is an optical communication system.

  The invention described in claim 10 is characterized in that the surface emitting laser element according to any one of claims 1 to 5 or the surface emitting laser array according to claim 7 is used as a light source. This is an optical interconnection system.

  According to the first to fourth aspects of the present invention, the current confinement structure that includes the active layer, the current blocking portion, and the conductive portion that defines the current injection region to the active layer is opposed to the active layer. In the surface emitting laser device including a pair of distributed Bragg reflectors, the current blocking portion is formed by a multilayer structure including a plurality of heterointerfaces in which semiconductor layers having different band gap energies are alternately stacked. Therefore (that is, the current blocking portion is formed by a multilayer structure including a plurality of hetero interfaces), it is possible to obtain a current confinement structure with low leakage current and high confinement efficiency. As a result, a current confinement structure can be formed without generating a strain stress around the current confinement structure as in a surface emitting laser element (selective oxidation type surface emitting laser element) having a selective oxidation structure as a current confinement structure. it can. In addition, the current confinement structure of the present invention can be obtained by a semiconductor process such as photoengraving and etching having excellent controllability without using a selective oxidation process in which it is difficult to obtain high controllability, uniformity and reproducibility. Since it is formed, high device yield and reliability can be obtained.

  In particular, according to a second aspect of the present invention, in the surface-emitting laser device according to the first aspect, the conducting portion has a band gap energy between semiconductor layers having different band gap energies forming the current blocking portion. Since it is composed of layers, the resistance due to the potential barrier in the conduction part can be reduced, and the conduction part can have a low resistance. As a result, it is possible to provide a surface emitting laser element having higher constriction efficiency and lower element resistance.

  According to a third aspect of the present invention, in the surface emitting laser element according to the first aspect, the conducting portion is a semiconductor having a small band gap energy among the semiconductor layers forming the current blocking portion and having different band gap energies. Since it is composed of a semiconductor layer having a smaller band gap energy than the layer, it is possible to form an actual refractive index waveguide structure in which the current blocking portion is a low refractive index region and the conducting portion is a high refractive region. As a result, the transverse mode can be stably confined by the current confinement structure. In addition, since the current confinement structure of the present invention is entirely made of a semiconductor material, the refractive index difference is smaller than that of the current confinement structure using the selective oxidation structure. As a result, even if the area is relatively large, Single fundamental transverse mode oscillation can be obtained. In addition, since a single fundamental transverse mode oscillation can be obtained even in a relatively large current confinement area, the operating voltage of the element can be reduced. From the above, it is possible to provide a surface emitting laser element that is highly reliable and capable of single fundamental transverse mode oscillation up to high output.

  According to a fourth aspect of the present invention, in the surface emitting laser element according to any one of the first to third aspects, the multilayer structure in which semiconductor layers having different band gap energies are alternately stacked A semiconductor layer having a relatively small band gap energy among the semiconductor layers having different band gap energies in the vicinity of the position corresponding to the node of the standing wave of light, and in the vicinity of the position corresponding to the antinode of the standing wave In addition, since the semiconductor layer having a relatively large band gap energy among the semiconductor layers having different band gap energies is provided, lateral mode confinement can be performed more effectively. That is, in the configuration of claim 4, for example, among the semiconductor layers (semiconductor layers having different band gap energies) in which the conducting portion forms the heterostructure of the current blocking portion, the band gap energy is small (the refractive index is large). Even in the case of a semiconductor layer, a refractive index waveguide structure can be formed, and the transverse mode can be stably confined. As described above, in the invention of claim 4, the transverse mode confinement can be performed stably even for the configuration of a wider range of current confinement structure.

  According to a fifth aspect of the present invention, in the surface-emitting laser element according to any one of the first to fourth aspects, each semiconductor layer constituting the multilayer structure of the current blocking portion is a non-doped semiconductor. Therefore, by increasing the bulk resistance of the semiconductor layer and increasing the thickness of the potential barrier at the hetero interface, the current blocking portion can be further increased in resistance and current confinement can be performed with high efficiency.

  According to a sixth aspect of the present invention, in the method for manufacturing a surface emitting laser element according to any one of the first to fifth aspects, the conducting portions are semiconductor layers having different band gap energies. Is formed by interdiffusion of group III elements into a multilayer structure including a plurality of heterointerfaces alternately stacked (that is, the heterobarrier part is disordered by the group III element interdiffusion, and the conduction part (low resistance region ), The current confinement structure can be formed without using an etching process or the like. Thereby, the manufacturing process of an element can be simplified. Further, since etching or the like is not required, a flat element surface can be obtained, and an effect that process processing in a subsequent process is facilitated can be obtained.

  According to a seventh aspect of the present invention, there is provided a surface emitting laser array comprising a plurality of the surface emitting laser elements according to any one of the first to fifth aspects. Since the surface emitting laser array is composed of the surface emitting laser elements having high power conversion efficiency and reliability and capable of single basic transverse mode operation up to high output, the power conversion efficiency and reliability are high. It is possible to provide a surface emitting laser array having a low resistance and capable of oscillating in a single fundamental transverse mode up to a high output and suitable as a light source for an electrophotographic system such as a multi-beam writing system or an optical communication system.

  According to the invention described in claim 8, the surface emitting laser element according to any one of claims 1 to 5 or the surface emitting laser array according to claim 7 is used as a light source. This is an electrophotographic system characterized by high power conversion efficiency and reliability, and high reliability by using a surface-emitting laser element or surface-emitting laser array capable of single basic transverse mode operation up to high output. It is possible to provide a high-speed and high-definition electrophotographic system with low power consumption. In particular, when the surface emitting laser array according to claim 7 is used as a light source, the surface emitting laser array according to claim 7 has a high positional accuracy between the arrays, and therefore, a plurality of beams can be emitted from the same lens. It can be easily condensed with good reproducibility. Therefore, an optical system is simple and a low-cost system can be obtained.

  According to the invention described in claim 9, the surface emitting laser element according to any one of claims 1 to 5 or the surface emitting laser array according to claim 7 is used as a light source. This optical communication system features high power conversion efficiency and reliability, and is highly reliable by using a surface-emitting laser element or surface-emitting laser array capable of single basic transverse mode operation up to high output. It is possible to provide an optical communication system with low power consumption and capable of high-speed and long-distance communication.

Further, according to the invention described in claim 10, the surface emitting laser element according to any one of claims 1 to 5 or the surface emitting laser array according to claim 7 is used as a light source. The optical interconnection system is characterized by high power conversion efficiency and reliability, and by using a surface-emitting laser element or surface-emitting laser array capable of single basic transverse mode operation up to high output, reliability is achieved. It is possible to provide an optical interconnection system that is high, has low power consumption, and can perform high-speed transmission.

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

(First form)
According to a first aspect of the present invention, a current confinement structure that includes an active layer, a current blocking portion, and a conduction portion and defines a current injection region into the active layer, and a pair provided opposite to each other with the active layer interposed therebetween. In the surface emitting laser device including the distributed Bragg reflector, the current blocking portion is formed of a multilayer structure including a plurality of heterointerfaces in which semiconductor layers having different band gap energies are alternately stacked. It is said.

  It is known that spike and notch-like potential barriers are formed at the heterointerfaces of semiconductor layers having different band gap energies due to band discontinuities in the respective semiconductor layers. Electrons and holes that are carriers are prevented from conducting by a spike-like potential barrier, and a semiconductor structure including a heterointerface has a higher resistance than a normal bulk semiconductor. Further, among electrons and holes, holes have a larger effective mass and are more affected by the potential barrier. Therefore, a p-type semiconductor in which holes are majority carriers has a property of easily increasing resistance due to the influence of the heterointerface.

  In the first embodiment of the present invention, a multilayer structure including a plurality of heterointerfaces in which semiconductor layers having different band gap energies are alternately stacked is provided as a current blocking portion of a current confinement structure. Since the current blocking portion has a high resistance due to the potential barrier generated at the hetero interface, the injected carriers can be confined to the conducting portion. In the first embodiment, the current confinement structure is formed without using the selective oxidation step of the semiconductor layer containing Al, which requires the management of very precise process conditions like the selective oxidation type surface emitting laser element. Therefore, a high device yield can be obtained. Further, since the selective oxidation layer is not used, there is no problem such as generation of strain stress at the selective oxidation interface, and the reliability of the element is high. Note that the current confinement structure can be provided in either the n-type semiconductor or the p-type semiconductor. However, as described above, the semiconductor material is a hole that is a majority carrier of the p-type semiconductor material. Since this is more susceptible to the potential barrier, a larger constriction effect can be obtained when it is provided in a p-type semiconductor. As described above, in the present invention, it is possible to reduce reactive current that does not contribute to laser oscillation compared to the case where a high resistance layer made of a conventional semiconductor material is used as a current confinement layer, and a low threshold current, A surface emitting laser element with high power conversion efficiency can be provided.

(Second form)
According to a second aspect of the present invention, in the surface-emitting laser device according to the first aspect, the conducting portion has a semiconductor layer having a band gap energy between semiconductor layers having different band gap energies forming the current blocking portion. It is characterized by comprising.

  In order to obtain a high current confinement effect by a multilayer structure in which semiconductor layers having different band gap energies are alternately stacked, two types of forming a multilayer structure with respect to an arbitrary semiconductor layer in contact with the multilayer structure in a surface emitting laser element Of these semiconductor layers, it is desirable to provide a material having a composition that increases the band discontinuity with any semiconductor layer.

  In order to obtain a particularly high confinement efficiency, it is preferable to confine holes among the two types of carriers as described above. In this case, the band discontinuity on the valence band side is increased. It is desirable to provide a multilayer structure. Furthermore, the band energy of the valence band tends to decrease with increasing band gap energy in many semiconductor materials.

  In the second embodiment of the present invention, when the configuration of the current blocking portion having a multilayer structure as described above is selected, the valence band discontinuity with any semiconductor layer in contact with the conducting portion in the conducting portion is The valence band band discontinuity with respect to the current blocking part can always be set small, reducing the resistance due to the potential barrier formed in the conducting part (the resistance of the conducting part can be reduced), Element resistance can be reduced. Further, by reducing the resistance of the conducting portion, a high confinement efficiency can be obtained, and a surface emitting laser element having a low threshold current and high power conversion efficiency can be provided. Such a structure for reducing the resistance of the conducting portion can be easily formed by using mutual diffusion of group III elements accompanying impurity diffusion or the like, as will be described later.

(Third form)
According to a third aspect of the present invention, in the surface-emitting laser device according to the first aspect, the conductive portion is a semiconductor layer having a small band gap energy among semiconductor layers having different band gap energies forming the current blocking portion. Further, it is characterized by being composed of a semiconductor layer having a smaller band gap energy. That is, in the third embodiment, among the semiconductor layers having different band gap energies forming the current blocking portion, the conducting portion is configured by a semiconductor layer having a smaller band gap energy than a semiconductor layer having a smaller band gap energy. .

  In the third embodiment of the present invention, the injected carrier can be confined to the conducting portion with high efficiency by the multilayer structure including a plurality of hetero interfaces as in the first embodiment of the present invention. Furthermore, there is a corresponding relationship between the refractive index of the semiconductor and the band gap energy, especially in mixed crystal materials of the same material system, a semiconductor mixed crystal having a small band gap energy (on the conduction band Γ point and the top of the valence band). The higher the refractive index, the more the property. Therefore, when the conducting portion is formed of a semiconductor layer having a smaller band gap energy than the semiconductor layer forming the current blocking portion as in the third embodiment, a transverse mode real refractive index confinement structure can be obtained. Further, since the current confinement structure is made of a semiconductor material, the refractive index difference between the current blocking portion and the conduction portion is smaller than that of the current confinement structure using the conventional selective oxidation structure. In the current confinement structure using the conventional selective oxidation structure, since the above refractive index difference is large, a very large transverse mode is confined. In addition to the fundamental transverse mode, a high-order transverse mode is easily confined. There is a problem that it will be. For this reason, it is necessary to set the current confinement diameter (side) to be minute so that the cutoff condition for the higher-order transverse mode is satisfied. On the other hand, in the third embodiment, since the refractive index difference in the transverse mode confinement structure is small as described above, the current confinement diameter (side) is set larger than that of the conventional selective oxidation surface emitting laser element. Even in this case, it is possible to easily satisfy the cut-off condition for the high-order transverse mode. As a result, the constriction area (oscillation area) can be set large, and a larger output can be obtained. Furthermore, since the constriction area can be set large, the resistance (drive voltage) of the element can be reduced. Further, since the element resistance (driving voltage) can be reduced, heat generation is reduced, so that the saturation point of the output and differential resistance is also increased, and high-speed operation is facilitated.

(4th form)
According to a fourth aspect of the present invention, in the surface emitting laser element according to any one of the first to third aspects, the multilayer structure in which semiconductor layers having different bandgap energies are alternately stacked has a standing wave of oscillation light. A semiconductor layer having a relatively small band gap energy among the semiconductor layers having different band gap energies in the vicinity of the position corresponding to the node, and the bands adjacent to each other in the vicinity of the position corresponding to the antinode of the standing wave. A semiconductor layer having a relatively large band gap energy among semiconductor layers having different gap energies is provided. That is, in the fourth embodiment, in a multi-layer structure including a plurality of hetero interfaces formed by alternately laminating semiconductor layers having different band gap energies that form a current blocking portion, a node of a standing wave of oscillation light is used. A semiconductor layer having a relatively small band gap energy is located in the vicinity of the corresponding position, and a semiconductor layer having a relatively large band gap energy is located in the vicinity of the position corresponding to the antinode of the standing wave. It is set as the position where is located.

  In the fourth embodiment of the present invention, the transverse mode real refractive index waveguide structure made of a semiconductor material can be more efficiently formed by adopting the above configuration. That is, in the laser oscillation state, the oscillation light forms a standing wave in the element, and the electric field intensity of the oscillation light is large at a position where it hits the antinode of the standing wave, and is zero at a position corresponding to a node. Therefore, if a light confinement structure is provided in the plane corresponding to the antinode with a larger electric field strength, the transverse mode confinement can be performed more effectively. The current confinement structure of the present invention is formed by a multilayer structure of semiconductor layers having different band gap energies, and each semiconductor layer has a different refractive index value corresponding to the band gap energy. Therefore, for example, when the semiconductor layer of the conducting portion has band gap energy (refractive index) between the semiconductor layers forming the current blocking portion (semiconductor layers having different band gap energies), the current blocking portion Corresponding to the refractive index of the semiconductor layer, the waveguide structure and the anti-waveguide structure are alternately formed in the surface, and the transverse mode confinement may not be obtained efficiently. In such a case, among the semiconductor layers forming the current blocking portion, a semiconductor layer having a smaller refractive index (a semiconductor layer having a large band gap energy) is provided at a position corresponding to the antinode of the standing wave, and the refractive index is large. When a semiconductor layer (semiconductor layer with a small band gap energy) is provided in other parts (particularly at the position of the standing wave node), the confinement structure provided at the position corresponding to the antinode of the standing wave is dominant. Thus, an actual refractive index waveguide structure can be formed. Thus, in the fourth embodiment of the present invention, transverse mode confinement can be obtained more effectively.

(5th form)
According to a fifth aspect of the present invention, in the surface emitting laser element according to any one of the first to fourth aspects, each semiconductor layer constituting the multilayer structure of the current blocking portion is formed of a non-doped semiconductor. It is a feature. That is, the current blocking portion is formed from a non-doped semiconductor layer. As in the fifth embodiment, by configuring the current confinement portion having a multilayer structure with a non-doped semiconductor layer, it is possible to increase the resistance at the hetero interface portion and obtain a larger current confinement effect. . That is, a spike-like potential barrier is formed at the hetero interface. The height of this potential barrier is determined mainly by the band discontinuity between the two semiconductor layers forming the junction, and the thickness of the potential barrier is determined by the thickness of the depletion layer at the heterointerface. Further, the thickness of the depletion layer is mainly determined by the impurity doping density of the semiconductor layer forming the heterointerface, and the thickness increases as the doping density is lowered. Therefore, as in the fifth embodiment, when a multilayer structure including a plurality of heterointerfaces is configured by a non-doped semiconductor layer, the bulk resistance of the semiconductor layer is increased and the resistance is increased, and the potential barrier at the heterointerface portion is increased. As the width increases, the resistance becomes higher. Thus, a high current confinement effect can be obtained even during high voltage operation.

(Sixth form)
According to a sixth aspect of the present invention, in the method for manufacturing a surface emitting laser element according to any one of the first to fifth aspects, the conducting portion includes a plurality of heterostructures in which semiconductor layers having different band gap energies are alternately stacked. It is characterized by being formed by interdiffusion of group III elements into a multilayer structure including the interface. That is, in the sixth embodiment, the heterointerface portion is disordered by the interdiffusion of group III elements to form a conduction portion. That is, in a semiconductor superlattice structure such as AlGaAs or AlGaInP, when impurities such as Zn (zinc) are diffused, group III elements of the semiconductor layer forming the superlattice structure mutually diffuse together with the diffusion of Zn or the like. It is known that the superlattice structure is disordered. In the sixth embodiment of the present invention, a heterostructure is formed by diffusing an impurity element such as Zn into a region to be a conductive portion after forming a multilayer structure including a plurality of heterointerfaces that are current blocking portions. The resistance is reduced by disordering. Thus, in the sixth embodiment, the surface emitting laser element of any one of the first to fifth embodiments can be easily manufactured without requiring processing such as etching. In addition, since the element can be manufactured without performing an etching process or the like, the element surface portion is flat, and subsequent processes can be easily performed. At this time, if a multi-layer structure including a plurality of heterointerfaces forming the current blocking portion is constituted by a non-doped semiconductor layer, the current blocking portion has a higher resistance as described in the fifth embodiment. In addition, by conducting impurity diffusion, it is possible to form a conduction portion in which both the bulk resistance and the resistance at the heterointerface are low resistance.

(7th form)
A seventh aspect of the present invention is a surface emitting laser array characterized in that a plurality of surface emitting laser elements of any one of the first to fifth aspects are arranged. As described above, the surface emitting laser elements according to the first to fifth embodiments have a high current confinement efficiency, a high element reliability, and a high element by forming the current blocking portion with a multilayer structure including a plurality of hetero interfaces. Has yield. Furthermore, since it has a transverse mode confinement structure made of a semiconductor material, the transverse mode confinement is smaller than that of a selective oxidation surface-emitting laser element, and a single basic lateral width is achieved up to a high output even in a relatively large current confinement area (oscillation area). Mode oscillation is obtained. Accordingly, the surface-emitting laser array of the seventh embodiment formed by these surface-emitting laser elements similarly has high constriction efficiency, yield and reliability, and is capable of single fundamental transverse mode oscillation up to high output. An array can be provided.

(Eighth form)
An eighth aspect of the present invention is an electrophotography characterized in that the surface-emitting laser element of any one of the first to fifth embodiments or the surface-emitting laser array of the seventh embodiment is used as a light source. System. The surface-emitting laser element according to any one of the first to fifth embodiments or the surface-emitting laser array according to the seventh embodiment has a transverse mode confinement structure made of a semiconductor material, so that it is compared with a selective oxidation surface-emitting laser element. The transverse mode confinement is small, and a single fundamental transverse mode oscillation can be obtained up to a high output even in a relatively large current confinement area (oscillation area). Moreover, high confinement efficiency can be obtained by forming the current blocking portion with a heterostructure. In addition, since the outgoing beam is circular and has high positional accuracy between the arrays, multiple beams can be easily collected with high reproducibility using the same lens, so the optical system is simple and low cost. A simple electrophotographic system. Further, since a high output can be obtained in the basic transverse mode, when an array is used, particularly high-speed writing is possible, and a high-speed electrophotographic system can be provided.

(9th form)
According to a ninth aspect of the present invention, there is provided an optical communication system characterized in that the surface emitting laser element according to any one of the first to fifth aspects or the surface emitting laser array according to the seventh aspect is used as a light source. It is. The surface-emitting laser element of any one of the first to fifth forms or the surface-emitting laser array of the seventh form can oscillate to a high output in a single fundamental transverse mode and has high coupling with an optical fiber. The transverse mode is stable against changes in the operating state of the element. In addition, since the current confinement area (oscillation area) can be set large, the element resistance is low and high-speed operation can be obtained. Therefore, an optical communication system using these as a light source is an optical communication system with high reliability, and an optical communication system capable of long-distance communication because of high basic transverse mode output.

(10th form)
According to a tenth aspect of the present invention, there is provided an optical interconnection characterized in that the surface emitting laser element according to any one of the first to fifth aspects or the surface emitting laser array according to the seventh aspect is used as a light source. System. The surface-emitting laser element of any one of the first to fifth forms or the surface-emitting laser array of the seventh form can oscillate to a high output in a single fundamental transverse mode and has high coupling with an optical fiber. The transverse mode is stable against changes in the operating state of the element. In addition, since the current confinement area (oscillation area) can be set large, the element resistance is low and high-speed operation can be obtained. Therefore, an optical interconnection system using these as a light source is an optical interconnection system with high reliability.

  Examples of the present invention will be described below.

  FIG. 1 is a view showing a surface emitting laser element according to Example 1. FIG. The surface emitting laser element of FIG. 1 is a 1.3 μm band surface emitting laser element having a GaInNAs / GaAs multiple quantum well structure as an active layer.

The surface emitting laser element shown in FIG. 1 is crystal-grown by metal organic chemical vapor deposition (MOCVD), and trimethylaluminum (TMA), trimethylgallium (TMG), and trimethylindium (TMI) are used as group III materials. The arsine (AsH ₃ ) gas is used as the V group raw material. Moreover, carbon tetrabromide (CBr ₄ ) is used as the p-type dopant material, and hydrogen selenide (H ₂ Se) is used as the n-type dopant material. Further, dimethylhydrazine (DMHy) is used as a nitrogen raw material for the active layer. The structure will be described below according to the manufacturing process.

Specifically, the surface emitting laser element of FIG. 1 has 36 cycles on an n-GaAs substrate 101, with an n-GaAs buffer layer 102 and an n-Al _0.9 Ga _0.1 As / GaAs pair as one cycle. N-Al _0.9 Ga _0.1 As / GaAs lower semiconductor distributed Bragg reflector 103, non-doped GaAs resonator spacer 104, GaInNAs / GaAs multiple quantum well active layer 105, non-doped GaAs resonator spacer 106, 1.5 period P-Al _0.9 Ga _0.1 As / GaAs first upper semiconductor distributed Bragg reflector 107, p-Ga _0.5 In _0.5 P etch stop layer 108 with a thickness of 20 nm, non-doped Al _0.9 Ga A multilayer structure 109 of _0.1 As / Al _0.1 Ga _0.9 As is sequentially formed.

Here, except for the interface with the p-Ga _0.5 In _0.5 P etching stop layer 108, a hetero spike buffer layer (linear composition gradient layer) having a thickness of 30 nm is formed on each interface of the distributed Bragg reflector. To reduce resistance. Further, the thickness of each semiconductor layer constituting the distributed Bragg reflector including the hetero spike buffer layer is set such that the laser oscillation wavelength (λ = 1.3 μm) so as to satisfy the multiple reflection phase condition of the distributed Bragg reflector. In contrast, the thickness is λ / 4n (where n is the refractive index of each semiconductor layer with respect to the laser oscillation wavelength, which is the same in the following examples). The specific thickness of each semiconductor layer constituting the distributed Bragg reflector in Example 1 is 78.8 nm for the Al _0.9 Ga _0.1 As layer and 66.3 nm for the GaAs layer. These layer thicknesses are similarly adjusted in the following other examples in accordance with the oscillation wavelength and the refractive index.

The multilayer structure 109 of non-doped Al _0.9 Ga _0.1 As / Al _0.1 Ga _0.9 As has the same thickness, and the total phase change in these semiconductor layers is 2π · The thickness is (2/4) (2λ / 4n equivalent thickness). Specifically, the thickness of one layer is set to about 37.5 nm, and 5.5 periods are stacked so that the uppermost layer and the lowermost layer of the multilayer structure are Al _0.9 Ga _0.1 As layers. Here, the constituent period of the multilayer structure 109 of non-doped Al _0.9 Ga _0.1 As / Al _0.1 Ga _0.9 As may be other than the above. Increasing the number of periods by reducing the thickness of each semiconductor layer of the multilayer structure 109 within a range in which the tunnel current does not increase can increase the number of heterointerfaces and increase the resistance. Further, as the thickness of each semiconductor layer of the multilayer structure 109 becomes thinner with respect to the oscillation wavelength, the interference effect of multiple reflection at each interface can be reduced.

Next, a circular resist pattern having an opening having a diameter of 10 μm is formed at the center of the surface emitting laser element of FIG. 1 using a known photolithography technique, and then a p-Ga _0.5 In _0.5 P etching stop layer. 108, the layered structure 109 of Al _0.9 Ga _0.1 As / Al _0.1 Ga _0.9 As that hits the resist opening is removed using a sulfuric acid-based etchant. Next, after removal of the resist and appropriate surface cleaning treatment, crystal growth of the 3λ / 4n-thick p-GaAs layer 110 is performed as the second crystal growth, and then 23 cycles of p-Al _0. Crystal growth of the ₉ Ga _0.1 As / GaAs second upper distributed Bragg reflector 111 is performed. Here, a hetero spike buffer layer (composition gradient layer) is not provided at the interface between the 3λ / 4n-thick p-GaAs layer 110 and the p-Ga _0.5 In _0.5 P etching stop layer 108. . Further, a contact layer (not shown) having an increased doping concentration in the vicinity of the outermost surface is provided on the GaAs layer serving as the outermost surface layer of the second upper distributed Bragg reflector 111. Here, of the two types of semiconductor layers constituting the multilayer structure 109, the semiconductor layer having a large band gap energy has a Ga composition in order to reduce the natural oxidation of the etching end face and facilitate the regrowth process. It is desirable to select a semiconductor layer containing.

2A and 2B show this state. In FIG. 2A, Al _0.9 Ga ₀ provided between the first and second upper distributed portion Bragg reflectors 107 and 111 and the first and second upper distributed portion Bragg reflectors 107 and 111. multilayer structure 109, and 3 [lambda] / 4n thickness of the p-GaAs layer 110 is shown, in accordance with _{.1 As / Al 0.1 Ga 0.9 As} . FIG. 2B shows the detailed structure of the region A in FIG. That is, in FIG. 2B, the p-Al _0.9 Ga _0.1 As / GaAs first upper semiconductor distributed Bragg reflector 107 constituting the p-Al _0.9 Ga _0.1 As / GaAs first p-Al _0.9 Ga _0. Each layer between a ₁ As layer and a 3λ / 4n thick p-GaAs layer 110 is shown.

Next, a SiO ₂ layer 112 is formed on the entire surface of the wafer by vapor phase chemical deposition (CVD), and then aligned with the etching removal portion to form a light emitting portion and the surrounding SiO ₂ layer 112. Is removed. Next, a circular resist pattern having a diameter of 15 μm is formed in the region to be the light emitting portion, and p-side electrode material is deposited. Next, the electrode material of the light emitting part is lifted off, and the p-side electrode 113 is formed. Next, after polishing the back surface of the n-GaAs substrate 101, an n-side electrode 114 is formed on the back surface of the substrate 101 by vapor deposition, and ohmic conduction between the electrodes 113 and 114 is achieved by annealing.

Through the above _steps, in the region subjected to etching removal of _{Al 0.9 Ga 0.1 As / Al 0.1} Ga 0.9 As multilayer structure 109, p-GaAs layer of 3 [lambda] / 4n thick by regrowth 110 is provided to satisfy the phase condition of multiple reflection in the distributed Bragg reflector, and is formed as a p-type doped low resistance conduction portion 115. Similarly, a region where the multilayer structure 109 of Al _0.9 Ga _0.1 As / Al _0.1 Ga _0.9 As is not removed by etching is similarly used for Al _0.9 Ga _0.1 As / Al _0.1. Ga _0.9 as _{p-Al 0.9} a multilayer structure 109 is provided by the first crystal growth corresponding to the lower layer of this of Ga 0.1 as / GaAs _Al 0.9 Ga of the first upper semiconductor DBR 107 The phase condition of multiple reflection in the distributed Bragg reflector is satisfied by the _0.1 As layer, and in the same region, an Al _0.9 Ga _0.1 As / Al _0.1 Ga _0.9 As multilayer structure is formed. A high resistance region (current blocking portion) 116 is formed by the 109 hetero interface. Carriers (holes) injected from the upper part of the element are generated by the high resistance region (current blocking portion) 116 made of the Al _0.9 Ga _0.1 As / Al _0.1 Ga _0.9 As multilayer structure 109, p -It is confined to the conductive portion 115 made of a GaAs layer. Here, in the conductive portion 115, the p-Ga _0.5 In _0.5 P etching stop layer 108 having a band gap energy between Al _0.9 Ga _0.1 As and GaAs functions as a hetero spike buffer layer. In addition, the resistance of the conductive portion 115 is reduced.

  The current confinement structure using the potential barrier at the heterointerface in the surface emitting laser element of Example 1 was able to obtain a good current confinement even in a high injection region (high voltage application region). Furthermore, since the conducting portion 115 has a relatively high refractive index with respect to the constricted portion 116 in the same plane, an actual refractive index waveguide structure is formed in the lateral direction to confine the transverse mode. Things were possible. Further, since the difference in refractive index between the conducting portion 115 and the current blocking portion 116 of the surface emitting laser element of FIG. 1 is smaller than that of the conventional selective oxidation type surface emitting laser element, a relatively large constriction diameter (area of the conducting portion). It was also possible to obtain single fundamental transverse mode oscillation up to high output.

  FIG. 3 is a view showing a surface emitting laser element of Example 2. The surface emitting laser element of FIG. 3 is a 0.98 μm band surface emitting laser element having a GaInAs / GaAs multiple quantum well structure as an active layer, and was formed using the same growth method and raw material as the element of Example 1. Is.

The surface-emitting laser element of FIG. 3 has an n-GaAs substrate 201 on an n-GaAs buffer layer 202 and a 36-cycle n-Al with one n-Al _0.9 Ga _0.1 As / GaAs pair as one cycle. _0.9 Ga _0.1 As / GaAs lower semiconductor distributed Bragg reflector 203, non-doped GaAs resonator spacer 204, GaInAs / GaAs multiple quantum well active layer 205, non-doped GaAs resonator spacer 206, 1.5-period p-Al _0.9 Ga _0.1 As / GaAs first upper semiconductor distributed Bragg reflector 207, p-Ga _0.5 In _0.5 P etching stop layer 208, multilayer of non-doped Al _0.9 Ga _0.1 As / GaAs Structures 209 are formed sequentially. Here, also in Example 2, a hetero spike buffer layer (composition gradient layer) having a thickness of 30 nm is provided at the interface of each layer constituting the distributed Bragg reflector.

In Example 2, as shown in FIGS. 4A and 4B described later, in the non-doped Al _0.9 Ga _0.1 As / GaAs multilayer structure 209, it corresponds to the antinodes of the standing wave of the oscillation light. An Al _0.9 Ga _0.1 As layer having a large band gap energy (low refractive index) among the semiconductor layers constituting the multilayer structure 209 is provided in the vicinity of the region to be A GaAs layer having a small band gap energy (high refractive index) is provided in the vicinity of the semiconductor layers constituting the multilayer structure 209.

Next, similarly to Example 1, after forming a circular resist pattern having an opening with a side of 8 μm at the center of the surface emitting laser element of FIG. 3 using a known photolithography technique, p-Ga _0.5 With the In _0.5 P etching stop layer 208, the Al _0.9 Ga _0.1 As / GaAs multilayer structure 209 that hits the resist opening is removed using a sulfuric acid-based etchant. Next, after removal of the resist and appropriate surface cleaning treatment, as the second crystal growth, the p-GaAs layer 210 having a thickness of 3λ / 4n with respect to the laser oscillation wavelength (λ = 0.98 μm) is formed. Crystal growth is performed, and subsequently, 22-period p-Al _0.9 Ga _0.1 As / GaAs second upper distributed Bragg reflector 211 is grown. Here, a contact layer (not shown) having a higher doping concentration in the vicinity of the outermost surface is provided on the GaAs layer which is the outermost surface layer of the second upper distributed Bragg reflector 211.

Next, the SiO ₂ layer (insulating layer) 212, the circular p-side electrode 213 having a diameter of 15 μm aligned with the etching removal portion, and the n-side electrode 214 on the back surface of the substrate 201 by the same method and procedure as in Example 1. Form.

FIGS. 4A and 4B show this state. In FIG. 4A, Al _0.9 Ga _0.1 provided between the first and second upper distributed Bragg reflectors 207 and 211 and the first and second upper distributed Bragg reflectors 207 and 211. A multilayer structure of As / GaAs and a 3λ / 4n thick p-GaAs layer 210 are shown. FIG. 4B shows a detailed structure of the region A in FIG. That is, FIG. 4 (b) _{is, p-Al 0.9 Ga 0.1 As} / GaAs first upper semiconductor distributed Bragg reflector 207 constituting the lambda / 4n thick _p-Al 0.9 _{Ga 0.} Each layer between the ₁ As layer and the 3λ / 4n thick p-GaAs layer 210 is shown.

Here, specifically, in the multilayer structure 209 of non-doped Al _0.9 Ga _0.1 As / GaAs, as shown in FIG. 4B, Al _0.9 Ga is formed in a region corresponding to the antinode of the standing wave. _{A 0.1} As layer is provided and its thickness is set to 40 nm. Further, the thickness of the Al _0.9 Ga _0.1 As layer is relatively larger than the thickness of the GaAs layer in the peripheral region. ing. In addition, a GaAs layer is provided in a region corresponding to the node of the standing wave, the thickness thereof is set to 30 nm, and the thickness of the Al _0.9 Ga _0.1 As layer in the peripheral region is compared with the thickness of the GaAs layer. The thickness is relatively increased. As described above, the thickness of each layer is changed according to the standing wave distribution, and 3.5 periods are provided. The thicknesses of these two types of semiconductor layers are adjusted so that the total phase change in the multilayer structure 209 is 2π · 1/2 (1λ / 2n equivalent thickness). In the second embodiment, the period of the multilayer structure 209 and the thickness of each layer may be other than those described above.

In the surface-emitting laser element of Example 2, the area corresponding to 2π · (1/4) corresponds to the area where the non-doped Al _0.9 Ga _0.1 As / GaAs laminated structure 209 was etched and the area where this was not performed. Since a step is generated, when the second upper distributed Bragg reflector 211 is grown as the second crystal growth, a plane parallel to the substrate surface in the above-described etched region and the region where this etching is not performed is performed. In most of the areas, the same material is located in the two kinds of materials constituting the distributed Bragg reflector. Accordingly, the lateral confinement of light by these structures is very weak, and in the Al _0.9 Ga _0.1 As / GaAs multilayer structure 209, the position where each layer constituting this is provided and the thickness of each layer are described above. By adjusting as described above, it is possible to efficiently perform lateral mode confinement.

In the surface emitting laser element of this Example 2, the high resistance region 216 is formed by the hetero interface of the Al _0.9 Ga _0.1 As / GaAs multilayer structure 209 in the same manner as the surface emitting laser element of Example 1. Thus, carriers (holes) injected from the upper part of the element can be confined to the conduction part 215 made of the p-GaAs layer. The current confinement structure using the potential barrier at the heterointerface in the surface emitting laser element of Example 2 was able to obtain good current confinement even in the high injection region (high voltage application region).

  Furthermore, in the surface emitting laser element of Example 2, in the multilayer structure 209, the region corresponding to the antinode of the standing wave having a large electric field intensity of the oscillation light with respect to the conduction portion 215 in the same plane as the multilayer structure 209. By providing a semiconductor layer having a large bandgap energy (low refractive index) in the vicinity of, an actual refractive index waveguide structure could be easily formed. Also, since the difference in refractive index between the conducting portion 215 and the current blocking portion 216 of the surface emitting laser element of FIG. 3 is smaller than that of the conventional selective oxidation type surface emitting laser element, a relatively large constriction diameter (area of the conducting portion). In, the single fundamental transverse mode oscillation could be obtained up to high output.

FIG. 5 is a diagram showing a surface emitting laser element according to Example 3. The surface emitting laser element of FIG. 5 is a 0.78 μm band surface emitting laser element having an active layer of an Al _0.1 Ga _0.9 As / Al _0.35 Ga _0.65 As multiple quantum well structure. The surface-emitting laser element of Example 3 is formed using the same growth method and materials as those of the surface-emitting laser element of Example 1. The structure will be described below according to the manufacturing process.

The surface emitting laser element of FIG. 5 has an n-GaAs buffer layer 302 and an n-Al _0.9 Ga _0.1 As / Al _0.3 Ga _0.7 As pair on an n-GaAs substrate 301 for one period. 50.5 period n-Al _0.9 Ga _0.1 As / Al _0.3 Ga _0.7 As lower semiconductor distributed Bragg reflector 303, non-doped AlGaAs resonator spacer 304, Al _0.1 Ga _{0. 9} As / Al _0.35 Ga _0.65 As multiple quantum well active layer 305, non-doped AlGaAs resonator spacer 306, two periods of p-Al _0.9 Ga _0.1 As / Al _0.3 Ga _0.7 As A first upper semiconductor distributed Bragg reflector 307 and a multilayer structure 309 of non-doped AlAs / Al _0.3 Ga _0.7 As are sequentially formed.

Here, also in this Example 3, as in Example 2, in the non-doped AlAs / Al _0.3 Ga _0.7 As multilayer structure 309, in the vicinity of the region corresponding to the antinode of the standing wave of the oscillation light, Of the semiconductor layers constituting the multilayer structure 309, an AlAs layer having a large bandgap energy (small refractive index) is provided so as to be located in the vicinity of the region corresponding to the node of the standing wave. Among the layers, an Al _0.3 Ga _0.7 As layer having a small band gap energy (high refractive index) is provided. Further, the thicknesses of the two semiconductor layers are not constant, and the thickness of the AlAs layer having a large band gap energy (low refractive index) is relatively thick in the vicinity of the region corresponding to the antinode. In the vicinity of the region corresponding to, the thickness of the Al _0.3 Ga _0.7 As layer having a small band gap energy (high refractive index) is relatively large.

Next, using a known photoengraving technique, a circular resist opening pattern having a diameter of 8 μm is formed in a region to be the conducting portion 315 of the surface emitting laser element, and a multilayer structure of non-doped AlAs / Al _0.3 Ga _0.7 As Zn ions are implanted into 309. Next, after resist removal and appropriate surface cleaning, thermal annealing is performed in an AsH ₃ atmosphere to recover lattice damage by diffusion and implantation of Zn element. Then, _{p-AlAs /} Al 0.3 was _{Ga 0.7} As pair, 29 cycles of _{p-AlAs / Al 0.3 Ga 0.7} As second upper semiconductor DBR as the second crystal growth A vessel 311 is formed. Here, a p-GaAs contact layer (not shown) having a thickness of 20 nm is provided on the outermost surface layer.

Next, the SiO ₂ layer (insulating layer) 312, the circular p-side electrode 313 having a diameter of 15 μm aligned with the etching removal portion, and the n-side electrode 314 on the back surface of the substrate 301 are formed by the same method and procedure as in Example 1. Form.

FIGS. 6A and 6B show this state. FIG. 6A shows AlAs / Al _0.3 Ga ₀ provided between the first and second upper distributed Bragg reflectors 307 and 311 and the first and second upper distributed Bragg reflectors 307 and 311. A multilayer structure 309 with _.7 As is shown. FIG. 6B shows the detailed structure of the region B in FIG. That is, FIG. 6B shows a p-Al _0.3 Ga _0.7 .mu. / 4 n-thickness p-Al _0.3 Ga _{0. 5} constituting the p-AlAs / Al _0.3 Ga _0.7 As first upper semiconductor distributed Bragg reflector 307 _. Each layer between the ₇ As layer and the p-AlAs layer of λ / 4n thickness constituting the p-AlAs / Al _0.3 Ga _0.7 As second upper semiconductor distributed Bragg reflector 311 is shown.

Here, in the region where Zn is diffused, the conductivity type is p-type, the electric resistance is reduced, and the group III element is interdiffused along with the diffusion of Zn, and AlAs / Al _0.3 Ga _0.7. The multilayer structure 309 made of As is disordered, and a conducting portion 315 is formed. By interdiffusion of group III elements, the hetero interface is not steep, the resistance at the conducting portion 315 is reduced, and current flows more easily. Therefore, a current confinement structure is formed in which the region 316 where the Zn ions are not implanted is the current blocking portion and the region 315 where the Zn ions are implanted and the group III element is interdiffused is the conducting portion. Further, by appropriately setting Zn ion implantation conditions and thermal annealing conditions, ideally, a uniform semiconductor layer having an average composition of semiconductor layers forming a multilayer structure can be formed.

Here, specifically, the thickness of the multilayer structure 309 of non-doped AlAs / Al _0.3 Ga _0.7 As satisfies the Bragg multiple reflection phase condition for the mixed crystal composition after disordering. Similarly, it is formed to a thickness such that the phase change in the region is 2π · (3/4). The thickness of each semiconductor layer constituting the AlAs / Al _0.3 Ga _0.7 As multilayer structure 309 is as follows. As shown in FIG. 6B, an AlAs layer is provided in the vicinity of the antinode of the standing wave. Is 35 nm. In addition, an Al _0.3 Ga _0.7 As layer is provided in the vicinity of the node, and the thickness thereof is set to 35 nm. As described above, the thickness is changed according to the standing wave distribution, and five periods are provided.

Here, in the region where disorder occurs, an AlGaAs layer having a composition between AlAs and Al _0.3 Ga _0.7 As, which is the original structure, is formed, and the AlAs layer and the Al _0.3 Ga _{0. 7} A uniform AlGaAs layer having a composition corresponding to the ratio of the total thickness of the As layers is formed. Therefore, AlAs having a lower refractive index than that of the conducting portion and Al _0.3 Ga _0.7 As having a higher refractive index are alternately positioned in the plane of the conducting portion 315, and the refractive index with respect to the transverse mode. The waveguide structure and the refractive index anti-waveguide structure are formed at the same time. However, in the surface emitting laser element of this Example 3, in the multilayer structure 309 made of AlAs / Al _0.3 Ga _0.7 As, it corresponds to the antinodes of standing waves that have a greater influence on the transverse mode. By providing an AlAs layer at a position and further providing a relatively thick AlAs layer with respect to the Al _0.3 Ga _0.7 As layer in the periphery, the actual refractive index waveguide structure by the AlAs layer can be It is dominant over mode confinement, and transverse mode confinement is possible.

  In addition, since the current confinement structure in the surface emitting laser element of Example 3 is configured by the semiconductor structure as described above, the refractive index difference between the conduction portion 315 and the current blocking portion 316 is small, and a relatively large confinement diameter. It is also possible to obtain a single fundamental transverse mode oscillation. In Example 3, the conduction portion 315 was formed by Zn ion implantation and thermal diffusion, whereby the surface of the element was flat and the manufacturing process was simple.

  In each of the above-described Examples 1, 2, and 3, 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) are also available. The law can also be used. In addition to the 0.78 μm band, the 0.98 μm band, and the 1.3 μm band described above, the oscillation wavelength may be in a wavelength band such as a 0.65 μm band, a 0.85 μm band, and a 1.55 μm band. good. Further, as the semiconductor material constituting the element, other than the above may be used depending on the oscillation wavelength. For example, an AlGaInP-based mixed crystal can be used in the 0.65 μm band, an AlGaAs-based mixed crystal in the 0.85 μm band, and a GaInNAs (Sb) -based mixed crystal semiconductor material in the 1.55 μm band. In addition, the material and configuration of the distributed Bragg reflector can be optimally selected according to the oscillation wavelength, and any structure can form an element corresponding to an arbitrary oscillation wavelength. Specifically, a combination that is transparent with respect to the oscillation wavelength of the surface emitting laser element and has a refractive index difference as large as possible is preferable. Further, the element structure may be a structure other than that shown in each of the above-described embodiments, and the element shown in each of the above-described embodiments may have other oscillation wavelengths. In addition to the p-type distributed Bragg reflector, the position where the current confinement structure is provided may be in the n-type distributed Bragg reflector or in any place of the element. Further, the type of the semiconductor substrate may be other than GaAs, and the conductivity type of the substrate may be other than the embodiment.

  FIG. 7 is a view showing a surface emitting laser array of Example 4. That is, FIG. 7 shows a top view of a 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, in order to drive each surface emitting laser element independently, wiring is individually provided on the upper electrode. Further, the surface emitting laser array of FIG. 7 is manufactured by the same procedure and method as the above-described embodiments, and each surface emitting laser element constituting the surface emitting laser array is composed of a plurality of semiconductor heterogeneous elements. A current confinement structure including an interface is provided.

  Therefore, as described above, single fundamental transverse mode oscillation can be obtained up to a high output even when the current confinement area is set larger than that of the selective oxidation surface emitting laser element. In addition, since the current confinement area can be set large, the element has a low resistance and the output saturation point due to heat generation is also high. In addition, the current confinement structure is a structure including a plurality of semiconductor heterointerfaces, thereby providing high confinement efficiency. The surface emitting laser array of Example 4 oscillated in a single fundamental transverse mode up to a high output. As described above, in Example 4, a surface emitting laser array that operates at a high output in a single transverse mode 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) is condensed on a photosensitive drum by a scanning converging optical system including a polygon mirror and a lens converging system. Form an image. In the surface emitting laser array of the present invention, single fundamental transverse mode oscillation can be obtained up to a high output as described above. Accordingly, high-speed writing is possible, and the far-field image is unimodal, so that the beam can be easily collected and high-definition image quality can be obtained.

  FIG. 9 illustrates an optical interconnection system according to the sixth embodiment. The optical 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 laser array module using the surface emitting laser element or the surface emitting laser array 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.

The optical interconnection system of Example 6 uses the surface emitting laser array of the present invention, so that it stably oscillates in the fundamental transverse mode, and has a coupling ratio with the fiber with respect to changes in driving conditions such as environmental temperature. A highly reliable interconnection system can be configured with little change. 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.

1 is a diagram illustrating a surface emitting laser element of Example 1. FIG. It is the elements on larger scale of the surface emitting laser of FIG. 6 is a view showing a surface emitting laser element according to Example 2. FIG. FIG. 4 is a partially enlarged view of the surface emitting laser of FIG. 3. 6 is a view showing a surface emitting laser element according to Example 3. FIG. It is the elements on larger scale of the surface emitting laser of 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 Substrate 102 Buffer layer 103 Lower semiconductor distributed Bragg reflector 104, 106 Resonator spacer
105 active layer 107 first upper semiconductor distributed Bragg reflector 108 etching stop layer 109 multilayer structure 110 p-GaAs layer 111 second upper semiconductor distributed Bragg reflector 112 SiO ₂ layer 113 p-side electrode 114 n-side electrode 115 conducting portion 116 current Blocking part 201 Substrate 202 Buffer layer 203 Lower semiconductor distributed Bragg reflector 204, 206 Resonator spacer
205 active layer 207 first upper semiconductor distributed Bragg reflector 208 etching stop layer 209 multilayer structure 210 p-GaAs layer 211 second upper semiconductor distributed Bragg reflector 212 SiO ₂ layer 213 p-side electrode 214 n-side electrode 215 conducting portion 216 current Blocking part 301 Substrate 302 Buffer layer 303 Lower semiconductor distributed Bragg reflector 304, 306 Resonator spacer
305 active layer 307 first upper semiconductor distributed Bragg reflector 309 multilayer structure 311 second upper semiconductor distributed Bragg reflector 312 SiO ₂ layer 313 p-side electrode 314 n-side electrode 315 conducting portion 316 current blocking portion

Claims (10)

An active layer, a current confinement structure that defines a current injection region into the active layer, which includes a current blocking portion and a conduction portion, and a pair of distributed Bragg reflectors provided opposite to each other across the active layer In the surface emitting laser element, the current blocking portion is formed by a multilayer structure including a plurality of heterointerfaces in which semiconductor layers having different band gap energies are alternately stacked. 2. The surface emitting laser element according to claim 1, wherein the conducting portion is constituted by a semiconductor layer having a band gap energy between semiconductor layers having different band gap energies forming the current blocking portion. Surface emitting laser element. 2. The surface emitting laser device according to claim 1, wherein the conducting portion is a semiconductor having a smaller band gap energy than a semiconductor layer having a smaller band gap energy among semiconductor layers having different band gap energies forming the current blocking portion. A surface-emitting laser element characterized by comprising layers. 4. The surface emitting laser element according to claim 1, wherein the multilayer structure in which semiconductor layers having different band gap energies are alternately stacked corresponds to a standing wave node of oscillation light. A semiconductor layer having a relatively small band gap energy among the semiconductor layers having different band gap energies in the vicinity of the position, and the semiconductors having different band gap energies in the vicinity of the position corresponding to the antinodes of the standing wave A surface emitting laser element comprising a semiconductor layer having a relatively large band gap energy among the layers. 5. The surface emitting laser element according to claim 1, wherein each of the semiconductor layers constituting the multilayer structure of the current blocking portion is formed of a non-doped semiconductor. Laser element. 6. The method of manufacturing a surface-emitting laser element according to claim 1, wherein the conductive portion includes a plurality of heterointerfaces in which semiconductor layers having different band gap energies are alternately stacked. A method of manufacturing a surface-emitting laser element, characterized in that the surface-emitting laser element is formed by mutual diffusion of group III elements. A surface-emitting laser array comprising a plurality of surface-emitting laser elements according to any one of claims 1 to 5 arranged in an array. An electrophotographic system using the surface emitting laser element according to any one of claims 1 to 5 or the surface emitting laser array according to claim 7 as a light source. An optical communication system, wherein the surface emitting laser element according to any one of claims 1 to 5 or the surface emitting laser array according to claim 7 is used as a light source. An optical interconnection system, wherein the surface-emitting laser element according to any one of claims 1 to 5 or the surface-emitting laser array according to claim 7 is used as a light source.

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