JP5309877B2 - Photonic crystal surface emitting laser element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photonic crystal surface light emitting laser element oscillating at room temperature and stably operated while simplifying the manufacture process thereof, and to provide a method of manufacturing the same. <P>SOLUTION: The surface light emitting laser 1 includes: an active layer 13; an n-clad layer 12 and a p-clad layer 14 disposed so as to hold the active layer 13 therebetween; a photonic crystal layer 15 formed on the surface of the p-clad layer 14 and made independent of the active layer 13; and a p-type surface electrode 16 formed so as to be in contact with the photonic crystal layer 15. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

The present invention relates to a photonic crystal surface-emitting laser element, and more specifically, while simplifying the manufacturing process, as well as a possible oscillation at room temperature, stably can operate photonic crystal surface emitting about the laser element.

  In recent years, by inserting a two-dimensional photonic crystal layer into the structure of a surface-emitting laser element, the photonic crystal layer functions as an optical resonator and a diffraction grating, thereby realizing a single mode oscillation and surface emission. Nick crystal surface emitting laser elements have been proposed (see, for example, Patent Documents 1 and 2). In the photonic crystal surface emitting laser element disclosed in Patent Document 1, by using a fusion method in which a photonic crystal layer is separately formed and the photonic crystal layer is fused to a substrate on which an active layer is formed, A photonic crystal layer is formed in the structure. Further, in the photonic crystal surface emitting laser element disclosed in Patent Document 2, a regrowth epi method is used in which a semiconductor layer is further epitaxially grown on the photonic crystal layer by utilizing a unique property of a gallium nitride (GaN) -based material. Used to form a photonic crystal layer in the structure.

Further, as an example of a photonic crystal surface emitting laser element, a defective photonic crystal laser in which a photonic crystal structure in which air holes penetrating from the element surface to the active layer are periodically arranged is formed in the structure has been proposed. (For example, refer nonpatent literature 1). In this defect-type photonic crystal laser, by introducing lattice defects due to air hole defects in the photonic crystal structure, a mode localized in the lattice defects is utilized to move in a direction perpendicular to the device surface. The laser oscillation is achieved.
Japanese Patent No. 3989333 International Publication No. 2006/062084 Pamphlet Raffaele Colombelli et al., SCIENCE, “Quantum Cascade Surface-Emitting Photonic Crystal Laser”, 21 November 2003, Vol. 302, p.1374-1377

  However, in the photonic crystal surface emitting laser elements disclosed in Patent Documents 1 and 2, a photonic crystal layer is disposed in the vicinity of the active layer, and the semiconductor layer is provided between the photonic crystal layer and the electrode. A structure in which a clad layer is disposed is employed. As a result, in order to form this cladding layer on the photonic crystal layer, there is a problem that it is necessary to employ a manufacturing process including complicated manufacturing processes such as a fusion bonding method and a regrowth epitaxy method.

  In addition, since the defect type photonic crystal laser disclosed in Non-Patent Document 1 strongly confines the localized mode in the defect portion, it is necessary to maximize the light emission in the active layer and the optical coupling strength of the photonic crystal. The air holes of the photonic crystal reach the active layer. As a result, laser light oscillation occurs only in an extremely low temperature environment. For example, it is difficult to oscillate laser light at room temperature. This is because there are many exposed side walls of air holes in the active layer, and at room temperature, non-radiative recombination of carriers is very likely to occur on the exposed surface (surface recombination rate is very fast). It is. Therefore, in order to realize light emission and oscillation in the laser element disclosed in Non-Patent Document 1, it is necessary to cool the entire element to an extremely low temperature of about the liquid helium temperature (4K) in order to reduce the surface recombination speed. . Therefore, the laser element disclosed in Non-Patent Document 1 is difficult to use at room temperature, and is difficult to be applied in practice.

  Further, in the defect type photonic crystal laser, in order to confine the localized mode strongly in the defect part, it is necessary to minimize the volume of the defect part itself to the wavelength level. For this reason, it is difficult to increase the amount of localized light, and high-power laser oscillation is considered difficult. Also, even if high-power oscillation is successful, the emitted light is emitted from a very narrow defect surface, so that light concentration occurs on this defect surface and an end face destruction phenomenon (sudden death phenomenon called COD) ) Can easily occur. For this reason, it has been difficult to produce a highly reliable element.

  The present invention has been made to solve the above-described problems. That is, an object of the present invention is to provide a photonic crystal surface emitting laser element that can oscillate at room temperature and can operate stably while simplifying the manufacturing process, and a manufacturing method thereof.

A photonic crystal surface emitting laser element according to the present invention includes an active layer, a semiconductor layer disposed so as to sandwich the active layer, a two-dimensional diffraction grating formed on the surface of the semiconductor layer and independent of the active layer, And an electrode formed in contact with the entire two-dimensional diffraction grating. The two-dimensional diffraction grating functions alone as an optical resonator. The two-dimensional diffraction grating has a low refractive index portion and a high refractive index portion having a refractive index higher than the refractive index of the low refractive index portion. The high refractive index portion is made of a semiconductor, and the low refractive index portion is a hole formed in the high refractive index portion. The wavelength of light emitted from the active layer is in the range of 1.5 μm or more and 8 μm or less.

  In the photonic crystal surface emitting laser element of the present invention, since the two-dimensional diffraction grating is formed independently of the active layer, the recesses (such as air holes) constituting the two-dimensional diffraction grating reach the active layer. As is the case, the active layer is not damaged or exposed to the air due to the formation of the recess. Therefore, non-radiative recombination of carriers is less likely to occur than when the concave portion of the two-dimensional diffraction grating reaches the active layer, and sufficient light emission at room temperature can be realized. Further, in the photonic crystal surface emitting laser element of the present invention, it is possible to suppress the light concentration by increasing the emission surface, so that the defect type photonic crystal laser disclosed in Non-Patent Document 1 is used. It is unlikely that an end face destruction phenomenon will occur, and high reliability can be realized. Furthermore, in the photonic crystal surface emitting laser element of the present invention, an electrode is formed so as to be in contact with the two-dimensional diffraction grating, and a semiconductor layer such as a cladding layer is formed between the two-dimensional diffraction grating and the electrode. There is no need to do. As a result, it is not necessary to employ a manufacturing process including complicated manufacturing processes such as a fusion bonding method and a regrowth epitaxy, and it is possible to manufacture by a simple manufacturing process.

  As described above, according to the photonic crystal surface emitting laser element of the present invention, the photonic crystal surface emitting laser element that can oscillate at room temperature and can operate stably while simplifying the manufacturing process. Can be provided.

Further, the two-dimensional diffraction grating having such a configuration can be formed by a relatively simple process of forming a semiconductor layer to be a high refractive index portion and forming a hole by etching or the like. Therefore, the manufacturing process can be simplified, and a low-cost photonic crystal surface emitting laser element can be realized.

A photonic crystal surface emitting laser element according to the present invention includes an active layer, a semiconductor layer disposed so as to sandwich the active layer, a two-dimensional diffraction grating formed on the surface of the semiconductor layer and independent of the active layer, And an electrode formed in contact with the entire two-dimensional diffraction grating. The two-dimensional diffraction grating may have a low refractive index portion and a high refractive index portion having a refractive index higher than the refractive index of the low refractive index portion. The high refractive index portion is made of a semiconductor, and the low refractive index portion can include a dielectric disposed inside a hole formed in the high refractive index portion.

  The two-dimensional diffraction grating having such a configuration can be formed by a relatively simple process of forming a semiconductor layer to be a high refractive index portion, forming a hole by etching, and forming a dielectric inside the hole. Therefore, the manufacturing process can be simplified, and a low-cost photonic crystal surface emitting laser element can be realized.

A photonic crystal surface emitting laser element according to the present invention includes an active layer, a semiconductor layer disposed so as to sandwich the active layer, a two-dimensional diffraction grating formed on the surface of the semiconductor layer and independent of the active layer, And an electrode formed in contact with the entire two-dimensional diffraction grating. The two-dimensional diffraction grating may have a low refractive index portion and a high refractive index portion having a refractive index higher than the refractive index of the low refractive index portion. The high refractive index portion can be made of a metal, and the low refractive index portion can be made of a semiconductor.

The two-dimensional diffraction grating having such a configuration is relatively easy to form a semiconductor layer to be a low refractive index portion, to form a metal by, for example, etching a hole, and to form a metal inside the hole. Can be formed by a simple process. Therefore, the manufacturing process can be simplified, and a low-cost photonic crystal surface emitting laser element can be realized.
In the photonic crystal surface emitting laser element, the wavelength of light emitted from the active layer is preferably in the range of 1.5 μm to 8 μm.
By adopting such an active layer that emits light in the mid-infrared region, the region in which the evanescent light spreads becomes wider, and even if the distance between the active layer and the two-dimensional diffraction grating is increased, the evanescent light is two-dimensional. It is possible to reach the diffraction grating. Therefore, it becomes easy to employ the structure of the photonic crystal surface emitting laser element of the present invention in which the two-dimensional diffraction grating is disposed at a position in contact with the electrode.

A method of manufacturing a photonic crystal surface emitting laser device according to the present invention includes a step of forming an active layer, a step of forming a semiconductor layer on the active layer, and a two-dimensional diffraction independent of the active layer on the semiconductor layer. A step of forming a grating, and a step of forming an electrode in contact with the entire two-dimensional diffraction grating. The step of forming the two-dimensional diffraction grating can include a step of forming a base layer constituting the two-dimensional diffraction grating on the semiconductor layer and a step of forming a recess in the base layer. The step of forming an electrode includes a step of forming a conductor layer constituting a part of the electrode on the base layer and a step of forming another conductor layer constituting the electrode on the conductor layer. Can be included. Further, in the step of forming the recess, the recess may be formed by partially removing the conductor layer and the base layer by etching. In the step of forming another conductor layer, the other conductor layer is grown in the lateral direction by using a plating method, whereby the upper portion of the recess in the base layer can be closed by another conductor.

  In this way, the photonic crystal surface emitting laser element of the present invention can be easily manufactured. In addition, since the two-dimensional diffraction grating is formed on the semiconductor layer and the electrode is formed so as to be in contact with the two-dimensional diffraction grating, it is not necessary to perform complicated steps such as a fusion method or an epi-regrowth method. . Therefore, the manufacturing process of the photonic crystal surface emitting laser element can be simplified and the manufacturing cost can be reduced.

Further, by adopting such a manufacturing process, a two-dimensional diffraction grating configured by forming a plurality of holes (holes filled with air) in the base layer can be easily formed.

A method of manufacturing a photonic crystal surface emitting laser device according to the present invention includes a step of forming an active layer, a step of forming a semiconductor layer on the active layer, and a two-dimensional diffraction independent of the active layer on the semiconductor layer. A step of forming a grating, and a step of forming an electrode in contact with the entire two-dimensional diffraction grating. The step of forming the two-dimensional diffraction grating includes a step of forming a base layer constituting the two-dimensional diffraction grating on the semiconductor layer, a step of forming a recess in the base layer, and a dielectric layer filling the inside of the recess. Forming the process. The step of forming an electrode includes a step of forming a conductor layer constituting a part of the electrode on the base layer and a step of forming another conductor layer constituting the electrode on the conductor layer. May be included. In this case, in the step of forming the recess, the recess may be formed by partially removing the conductor layer and the base layer by etching. In the step of forming the other conductor layer, the other conductor layer is grown in the lateral direction by using a plating method, so that the upper portion of the recess in the base layer on which the dielectric layer is formed is replaced with the other conductor. You may make it close by.

  By adopting such a manufacturing process, it is possible to easily form a two-dimensional diffraction grating constituted by forming a plurality of recesses filled with a dielectric layer in the base layer.

A method of manufacturing a photonic crystal surface emitting laser device according to the present invention includes a step of forming an active layer, a step of forming a semiconductor layer on the active layer, and a two-dimensional diffraction independent of the active layer on the semiconductor layer. A step of forming a grating, and a step of forming an electrode in contact with the entire two-dimensional diffraction grating. The step of forming the two-dimensional diffraction grating may include a step of forming a base layer constituting the two-dimensional diffraction grating on the semiconductor layer and a step of forming a recess in the base layer. In this case, in the step of forming the electrode, the electrode may be formed so as to extend from the inside of the recess to the upper surface of the base layer.

  By adopting such a manufacturing process, it is possible to easily form a two-dimensional diffraction grating having a configuration in which a plurality of recesses in which a part of the electrode is filled in the base layer is formed.

  As is apparent from the above description, according to the photonic crystal surface emitting laser element and the manufacturing method thereof of the present invention, it is possible to oscillate at room temperature and to operate stably while simplifying the manufacturing process. A photonic crystal surface emitting laser element and a method for manufacturing the same can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

(Embodiment 1)
First, Embodiment 1 which is one embodiment of the present invention will be described. FIG. 1 is a schematic cross-sectional view showing a configuration of a surface emitting laser which is a photonic crystal surface emitting laser element in the first embodiment. FIG. 2 is a schematic perspective view showing a part of the configuration of the photonic crystal layer included in the surface emitting laser of FIG. FIG. 3 is a schematic plan view showing the configuration of the p-type surface electrode provided in the surface emitting laser of FIG.

  Referring to FIG. 1, surface emitting laser 1 in Embodiment 1 has a frequency ranging from the mid-infrared region to the terahertz (THz) band (wavelength is 1.5 μm or more and 1 mm or less), particularly a frequency in the mid-infrared region. This is a laser element capable of oscillating a laser beam (frequency is 1.5 μm or more and 8 μm or less).

  This surface-emitting laser 1 includes an n-substrate 11 whose conductivity type is n-type (first conductivity type), and an n-cladding as an n-type semiconductor layer disposed on one main surface of the n-substrate 11. A layer 12, an active layer 13 disposed on the n-cladding layer 12, a p-cladding layer 14 serving as a semiconductor layer of p-type (second conductivity type) disposed on the active layer 13, A photonic crystal layer 15 as a two-dimensional diffraction grating disposed on the p-cladding layer 14, a p-type surface electrode 16 disposed in contact with the photonic crystal layer 15, and n− in the n− substrate 11. An n-type back electrode 17 is provided on the main surface opposite to the side where the cladding layer 12 is disposed.

  The n − substrate 11 is made of, for example, GaSb (gallium antimony) and includes an n-type impurity, so that the conductivity type is n-type (first conductivity type). The n-cladding layer 12 is lattice-matched to the (001) plane of the n-substrate 11 and is made of, for example, AlGaAsSb (aluminum gallium arsenide antimony) and contains an n-type impurity, so that the conductivity type is n-type. .

  The active layer 13 is formed by alternately laminating barrier layers made of, for example, undoped AlGaSb (aluminum gallium antimony) without intentional impurity addition and well layers made of undoped InGaAsSb (indium gallium arsenide antimony). In addition, it has an MQW (Multi Quantum Well) structure.

  The p-cladding layer 14 is made of, for example, AlGaAsSb and includes a p-type impurity, so that the conductivity type is p-type (second conductivity type).

  Referring to FIGS. 1 and 2, photonic crystal layer 15 is made of, for example, AlGaAsSb, and includes a main layer 15A having a p-type conductivity by including a p-type impurity, and on main layer 15A. A contact layer 15B formed of, for example, GaSb (gallium antimony) and having a p-type conductivity by including a p-type impurity is included. The main layer 15A and the contact layer 15B constitute a base layer 15D, and holes 15C are formed as periodic recesses in the base layer 15D. More specifically, in the photonic crystal layer 15, holes 15 </ b> C that are air holes are arranged in a triangular lattice shape. As a result, the hole 15C is a low refractive index portion, and the surrounding base layer 15D is a high refractive index portion having a higher refractive index than the low refractive portion. Each of the holes 15C is formed at a position that becomes a lattice point of a triangular lattice, in other words, at a vertex position of an equilateral triangle. The distances between the center of one lattice point and the centers of the six lattice points adjacent to this lattice point are all equal. Note that the photonic crystal layer 15 and the active layer 13 are separated by, for example, 1 μm or more.

  That is, the photonic crystal layer 15 as a two-dimensional diffraction grating has a hole 15C as a low refractive index portion and a base layer 15D as a high refractive index portion having a refractive index higher than the refractive index of the hole 15C. ing. The base layer 15D is made of a semiconductor, and the holes 15C are holes formed in the base layer 15D.

  As shown in FIGS. 1 and 3, the p-type surface electrode 16 has the same planar shape as the planar shape of the hole 15 </ b> C at a position overlapping the hole 15 </ b> C that is an air hole in the photonic crystal layer 15 when viewed in plan. A hole 16A is formed. As a result, the p-cladding layer 14 is exposed from the hole 16A and the hole 15C. In addition, as a material which comprises the p-type surface electrode 16, various materials which can make ohmic contact with the contact layer 15B are employable.

  The n-type back electrode 17 is formed so as to cover the entire back surface of the n − substrate 11. In addition, as a material which comprises the n-type back surface electrode 17, various materials which can be in ohmic contact with the n-substrate 11 can be employed. For example, the same material as the p-type surface electrode 16 can be employed.

  Next, the operation of the surface emitting laser 1 in the present embodiment will be briefly described. Referring to FIG. 1, when a voltage is applied between p-type front electrode 16 and n-type back electrode 17, electrons from n-cladding layer 12 side and holes from p-cladding layer 14 side are activated. Implanted into layer 13. Then, the electrons and holes injected in the active layer 13 are recombined to generate light. Here, the generated light is, for example, light having a relatively long wavelength with a wavelength of 1.5 μm or more. The wavelength of the generated light can be adjusted by the configuration of the active layer 13.

  The light generated in the active layer 13 is confined in the active layer 13 by the n-cladding layer 12 and the p-cladding layer 14, but part of the light reaches the photonic crystal layer 15 as evanescent light. Here, since the structure of the active layer 13 is defined so that the light generated in the active layer 13 is light having a wavelength of 1.5 μm or more (for example, mid-infrared light), the region where the evanescent light spreads is widened. . This is because the spread of evanescent light is proportional to the wavelength of the light. Therefore, in the surface emitting laser 1 shown in FIG. 1, even if the distance between the photonic crystal layer 15 and the active layer 13 is, for example, 1 μm or more, evanescent light from the active layer 13 reaches the photonic crystal layer 15 sufficiently. To do. When the wavelength of the evanescent light that has reached the photonic crystal layer 15 coincides with the predetermined period of the photonic crystal layer 15, a standing wave is induced at the wavelength corresponding to the period.

  Such a phenomenon can occur in a region immediately below the p-type surface electrode 16 because the active layer 13 and the photonic crystal layer 15 are two-dimensionally widened. Laser oscillation can be caused by the feedback effect of the standing wave.

  The photonic crystal layer 15 (two-dimensional diffraction grating) has a property of overlapping when translated in the same period in at least two directions. Such a two-dimensional diffraction grating is formed by arranging regular triangles, squares, or regular hexagons all over the surface and providing a lattice point at each vertex. Here, a lattice formed using a regular triangle is referred to as a triangular lattice, a lattice formed using a square is referred to as a square lattice, and a lattice formed using a regular hexagon is referred to as a hexagonal lattice.

  FIG. 4 is a diagram for explaining light diffraction in a triangular lattice. The triangular lattice is filled with regular triangles whose side length is a. In FIG. 4, paying attention to a lattice point A arbitrarily selected from a plurality of lattice points (holes 15C), the direction from the lattice point A to the lattice point B is referred to as the X-Γ direction. The direction toward point C is called the XJ direction. Here, a case where the wavelength of light generated in the active layer 13 (see FIG. 1) corresponds to a lattice period in the X-Γ direction will be described.

The two-dimensional diffraction grating can be considered to include three one-dimensional diffraction grating groups L, M, and N described below. The one-dimensional diffraction grating group L includes one-dimensional gratings L ₁ , L ₂ , L _{3 and the} like provided in the Y-axis direction. The one-dimensional diffraction grating group M is composed of one-dimensional gratings M ₁ , M ₂ , M _{3 and the} like provided in the direction of an angle of 120 degrees with respect to the X-axis direction. The one-dimensional diffraction grating group N is composed of one-dimensional gratings N ₁ , N ₂ , N _{3 and the} like provided in a direction of 60 degrees with respect to the X-axis direction. These three one-dimensional diffraction grating groups L, N, and M overlap when rotated at an angle of 120 degrees around an arbitrary grating point. In each one-dimensional diffraction grating group L, N, and M, the interval between the one-dimensional gratings is d, and the interval within the one-dimensional grating is a.

  First, the lattice group L is considered. Light traveling in the direction from the lattice point A to the lattice point B causes a diffraction phenomenon at the lattice point B. The diffraction direction is defined by the Bragg condition 2d · sin θ = mλ (m = 0, ± 1,...). Here, λ is the wavelength of light in the base layer 15D (particularly the main layer 15A; see FIG. 2) which is a high refractive index portion. When the diffraction grating is formed so as to satisfy the second-order Bragg reflection (m = ± 2), other grating points D, E, F and G are formed at angles of θ = ± 60 ° and ± 120 °. Exists. There are also lattice points A and K at angles θ = 0 and 180 ° corresponding to m = 0.

  For example, light diffracted at the lattice point B in the direction of the lattice point D is diffracted according to the lattice group M at the lattice point D. This diffraction can be considered in the same manner as the diffraction phenomenon according to the grating group L. Next, the light diffracted toward the lattice point H at the lattice point D is diffracted according to the lattice group N. In this way, diffraction is sequentially performed at the lattice point H, the lattice point I, and the lattice point J. The light diffracted from the lattice point J toward the lattice point A is diffracted according to the lattice group N.

  As described above, the light traveling from the lattice point A to the lattice point B reaches the first lattice point A through a plurality of diffractions. For this reason, light traveling in a certain direction returns to the position of the original lattice point through a plurality of diffractions, so that a standing wave is generated between the lattice points. Therefore, this two-dimensional diffraction grating acts as an optical resonator, that is, a wavelength selector and a reflector.

  In the Bragg condition 2d · sin θ = mλ (m = 0, ± 1,...), The Bragg reflection direction under the condition that m is an odd number is θ = ± 90 °. This means that the diffraction becomes stronger in the direction perpendicular to the main surface of the two-dimensional diffraction grating. Thereby, referring to FIG. 1, light travels in a direction perpendicular to the main surface of the two-dimensional diffraction grating (main surface of photonic crystal layer 15), and follows the direction of arrow α through hole 15C and hole 16A. Light is emitted.

  Further, in this two-dimensional diffraction grating, the above-described light diffraction can occur at all the two-dimensionally arranged grating points. Therefore, light propagating in the X-Γ direction is two-dimensionally coupled to each other by Bragg diffraction, and a coherent state is formed. As described above, the surface emitting laser 1 in the present embodiment can function as a surface emitting element.

  FIG. 5 is a schematic perspective view showing another configuration of the photonic crystal layer. Referring to FIG. 5, photonic crystal layer 15 constitutes a two-dimensional diffraction grating having a square lattice form. Each of the holes 15C is formed at a position serving as a lattice point of a square lattice, in other words, at a vertex position of a square. The distances between the center of one lattice point (hole 15C) and the centers of the eight lattice points adjacent to this lattice point are all equal.

  FIG. 6 is a diagram for explaining light diffraction in a square lattice. The square lattice is filled with squares whose side length is d. In FIG. 6, paying attention to the arbitrarily selected lattice point W, the direction from the lattice point W to the lattice point P is called the X-Γ direction, and the direction from the lattice point W to the lattice point Q is the XJ direction. Call. Here, a case where the wavelength of light generated in the active layer 13 (see FIG. 1) corresponds to the lattice period in the X-Γ direction will be described.

The two-dimensional diffraction grating can be considered to include two one-dimensional diffraction grating groups U and V described below. The one-dimensional diffraction grating group U includes one-dimensional gratings U ₁ , U ₂ , U _{3 and the} like provided in the Y-axis direction. The one-dimensional diffraction grating group V includes one-dimensional gratings V ₁ , V ₂ , V _{3 and the} like provided in the X-axis direction. These two one-dimensional diffraction grating groups U and V overlap when rotated at an angle of 90 ° about an arbitrary grating point. In each one-dimensional diffraction grating group U and V, the interval between the one-dimensional gratings is d, and the interval within the one-dimensional grating is also d.

  First, the lattice group U will be considered. Light traveling in the direction from the lattice point W to the lattice point P causes a diffraction phenomenon at the lattice point P. The diffraction direction is defined by the Bragg condition 2d · sin θ = mλ (m = 0, ± 1,...) As in the case of the triangular grating. When the diffraction grating is formed so as to satisfy the second-order Bragg reflection (m = ± 2), there are other grating points Q and R at an angle θ = ± 90 °, and m = 0. There are also lattice points W and S at corresponding angles θ = 0 and 180 °.

  The light diffracted toward the lattice point Q at the lattice point P is diffracted according to the lattice group V at the lattice point Q. This diffraction can be considered in the same manner as the diffraction phenomenon according to the grating group U. Next, the light diffracted toward the lattice point T at the lattice point Q is diffracted according to the lattice group U. The light that is sequentially diffracted in this way and diffracted from the lattice point T toward the lattice point W is further diffracted according to the lattice group V.

  As described above, the light traveling from the lattice point W to the lattice point P reaches the first lattice point W through a plurality of diffractions. For this reason, in the semiconductor laser device of the present embodiment, light traveling in a certain direction returns to the position of the original lattice point through a plurality of diffractions, so that a standing wave is generated between the lattice points. Therefore, this two-dimensional diffraction grating acts as an optical resonator, that is, a wavelength selector and a reflector. Therefore, even when the photonic crystal layer 15 described with reference to FIGS. 5 and 6 is used instead of the photonic crystal layer 15 described with reference to FIGS. The laser 1 can function as a surface light emitting element.

  Here, the surface emitting laser 1 includes an n-substrate 11 that is a first conductivity type (n-type) substrate, an n-cladding layer 12 as an n-type semiconductor layer formed on the n-substrate 11, On the active layer 13 formed on the n-cladding layer 12, the p-cladding layer 14 as a second conductivity type (p-type) semiconductor layer formed on the active layer 13, and on the p-cladding layer 14 A photonic crystal layer 15 formed as a two-dimensional diffraction grating independent of the active layer 13 and a p-type surface electrode 16 formed so as to be in contact with the photonic crystal layer 15 are provided.

  That is, the surface emitting laser 1 is formed on the surface of the active layer 13, the n-cladding layer 12 and the p-cladding layer 14 as semiconductor layers arranged so as to sandwich the active layer 13, and the surface of the p-cladding layer 14. A photonic crystal surface-emitting laser element comprising a photonic crystal layer 15 as a two-dimensional diffraction grating independent of the active layer 13 and a p-type surface electrode 16 formed so as to be in contact with the photonic crystal layer 15. is there.

  In the surface emitting laser 1 in the present embodiment, the photonic crystal layer 15 is formed independently of the active layer 13 as described above. Therefore, unlike the case where the hole 15C constituting the photonic crystal layer 15 reaches the active layer 13, the active layer 13 is not damaged or exposed to the air due to the formation of the hole 15C. As a result, non-radiative recombination of carriers is less likely to occur than in the case where the hole 15C of the photonic crystal layer 15 reaches the active layer 13, and sufficient light emission at room temperature can be realized. Further, in the surface emitting laser 1 according to the present embodiment, it is possible to suppress light concentration by increasing the emission surface, and therefore, there is a possibility that an end face destruction phenomenon like a defective photonic crystal laser may occur. Low and stable operation. Furthermore, in surface emitting laser 1 in the present embodiment, p-type surface electrode 16 is formed so as to be in contact with photonic crystal layer 15, and between photonic crystal layer 15 and p-type surface electrode 16. There is no need to form a semiconductor layer such as a cladding layer. As a result, it is not necessary to employ a manufacturing process including complicated manufacturing processes such as a fusion bonding method and a regrowth epitaxy, and it is possible to manufacture by a simple manufacturing process.

  Note that the photonic crystal surface emitting laser elements disclosed in Patent Documents 1 and 2 described above are basically premised on lasers from near infrared light to visible light (with a wavelength of 0.4 μm or more and less than 1.5 μm). It is said. In this case, the region where the evanescent light spreads (the width is proportional to the wavelength) is small, and the photonic crystal layer needs to be formed in the vicinity of the active layer. Therefore, in Patent Documents 1 and 2, elements are formed using a fusion method or a regrowth method. However, in the surface emitting laser 1 according to the present embodiment, laser light in the THz band (wavelength of 1.5 μm or more and 1000 μm or less) from mid-infrared light, particularly mid-infrared light having a wavelength of 1.5 μm or more and 8 μm or less. Since laser light is used as an oscillation target, a region where the evanescent light spreads is widened. Therefore, the distance between the photonic crystal layer 15 and the active layer 13 can be greatly separated. Therefore, as shown in FIG. 1, it is possible to adopt a configuration in which the photonic crystal layer 15 is formed in contact with the p-type surface electrode 16. As a result, in the surface emitting laser 1 in the present embodiment, it is not essential to use a troublesome manufacturing method such as a fusion method or a regrowth method.

  Moreover, since the distance between the processing position of the hole 15C in the photonic crystal layer 15 and the active layer 13 is large, processing damage to the active layer 13 due to processing when forming the hole 15C hardly occurs. Similarly, the stress and strain generated when forming the photonic crystal layer 15 are less affected by the active layer 13. For this reason, it is also easy to adopt a dielectric column embedded photonic crystal structure, which has been difficult to employ in other short wavelength photonic crystal surface emitting laser elements due to the strength of residual stress. . As a result, the degree of freedom of structure is greatly expanded.

  As described above, the surface emitting laser 1 according to the present embodiment is a photonic crystal surface emitting laser element that can oscillate at room temperature and can operate stably while simplifying the manufacturing process. Yes.

  Next, a method for manufacturing the photonic crystal surface emitting laser element in the first embodiment will be described. FIG. 7 is a flowchart showing an outline of the method of manufacturing the photonic crystal surface emitting laser element in the first embodiment. 8 to 12 are schematic cross-sectional views for explaining the method for manufacturing the photonic crystal surface emitting laser element in the first embodiment. The surface emitting laser 1 in the present embodiment can be easily manufactured by the manufacturing method described below.

  Referring to FIG. 7, in the surface emitting laser manufacturing method according to the present embodiment, a substrate preparation step is first performed as a step (S10). Specifically, referring to FIG. 8, n-substrate 11 made of, for example, GaSb and having n-type conductivity is prepared. In addition to GaSb, InAs or the like can be used as a material for the substrate constituting the surface emitting laser of the present invention.

  Next, an n-cladding layer forming step is performed as a step (S20). In this step (S20), referring to FIG. 9, one main surface ((001) plane) of n-substrate 11 prepared in step (S10) is made of, for example, AlGaAsSb, and the conductivity type is n-type. N-cladding layer 12 is formed. The n-cladding layer 12 can be formed, for example, by epitaxially growing an AlGaAsSb layer containing an n-type impurity on the n-substrate 11. As the material of the n-cladding layer constituting the surface emitting laser of the present invention, for example, AlGaAsSb can be adopted when the substrate is GaSb, and when the substrate is InAs, GaAsSb, AlAsSb, etc. are adopted. can do.

  Next, an active layer forming step is performed as a step (S30). In this step (S30), the active layer 13 is formed on the n-cladding layer 12. Specifically, referring to FIG. 9, on the n-cladding layer 12 formed in the step (S20), a barrier layer made of undoped AlGaSb and a well layer made of undoped InGaAsSb are alternately repeated a plurality of times. To grow epitaxially. Thereby, an active layer 13 having an MQW structure in which barrier layers made of undoped AlGaSb and well layers made of undoped InGaAsSb are alternately stacked is formed. As a combination of the material of the barrier layer / well layer constituting the surface emitting laser of the present invention, AlInAs / InGaAsSb can be employed when the substrate is GaSb, and InAs / when the substrate is InAs. InAsSb, InGaAs / InSb, or the like can be used.

  Next, a p-type semiconductor layer forming step is performed as a step (S40). In this step (S40), referring to FIG. 9, p-type semiconductor layer 91 made of, for example, AlGaAsSb and having a p-type conductivity is formed on active layer 13 formed in step (S30). The p-type semiconductor layer 91 can be formed by epitaxially growing, for example, an AlGaAsSb layer containing a p-type impurity on the active layer 13. The p-type semiconductor layer 91 constitutes the p-cladding layer 14 and the main layer 15A of the photonic crystal layer 15 in the present embodiment. As a material for the p-cladding layer 14 and the main layer 15A of the photonic crystal layer 15 constituting the surface emitting laser of the present invention, AlGaAsSb can be adopted when the substrate is GaSb, and the substrate is made of InAs. In this case, AlAsSb, GaAsSb, or the like can be used.

  Next, a p-type contact layer forming step is performed as a step (S50). In this step (S50), referring to FIG. 9, second p-type semiconductor layer 92 made of, for example, GaSb and having a p-type conductivity is formed on p-type semiconductor layer 91 formed in step (S40). Is done. The formation of the second p-type semiconductor layer 92 can be performed by epitaxially growing, for example, a GaSb layer containing a p-type impurity on the p-type semiconductor layer 91. The second p-type semiconductor layer 92 constitutes the contact layer 15B of the photonic crystal layer 15 in the present embodiment. As a material for the contact layer constituting the surface emitting laser of the present invention, GaSb or the like can be adopted when the substrate is GaSb, and InAs or the like can be adopted when the substrate is InAs. . Moreover, the said process (S20)-(S50) can be implemented by MBE (Molecular Beam Epitaxy; molecular beam epitaxy) method, for example.

  Next, an electrode forming step is performed as a step (S60). In this step (S60), referring to FIG. 10, p-type surface electrode 16 made of a conductor is formed on the upper surface of second p-type semiconductor layer 92 using, for example, a vapor deposition method. In addition, an n-type back electrode 17 is formed on the back surface side of the n-substrate 11 (the back surface opposite to the surface on which the n-cladding layer 12 is formed) using an evaporation method.

  Next, as a step (S70), a recess forming step is performed. In this step (S70), a recess that penetrates the p-type surface electrode 16 and the second p-type semiconductor layer 92 and reaches the center in the thickness direction of the p-type semiconductor layer 91 is formed. With reference to FIG. 1, this recess constitutes hole 16 </ b> A of p-type surface electrode 16 and hole 15 </ b> C of photonic crystal layer 15.

  Specifically, referring to FIG. 11, first, a resist is applied on second p-type semiconductor layer 92 to form resist layer 99. Thereafter, exposure and development are performed, whereby openings 99A corresponding to the shapes and positions of the desired holes 16A and holes 15C are formed in the resist layer 99. Next, referring to FIGS. 11 and 12, p-type surface electrode 16 and second p-type semiconductor layer are formed by performing, for example, dry etching using resist layer 99 in which opening 99 </ b> A is formed as a mask. An air hole that penetrates 92 and reaches the center in the thickness direction of the p-type semiconductor layer 91 is formed. Thereby, a hole 16A is formed in the p-type surface electrode 16, and a hole 15C is formed in the photonic crystal layer 15. That is, in the thickness direction of the p-type semiconductor layer 91, a region where air holes are formed becomes the photonic crystal layer 15, and a region where no air holes are formed becomes the p-cladding layer 14. Thereafter, by removing resist layer 99, surface emitting laser 1 in the present embodiment shown in FIG. 1 is completed.

  By performing the steps (S10) to (S70) as described above, the surface emitting laser 1 according to the present embodiment can be easily manufactured without using a complicated fusion method or regrowth epi method. Can do.

(Embodiment 2)
Next, Embodiment 2 which is another embodiment of the present invention will be described. FIG. 13 is a schematic cross-sectional view showing a configuration of a surface emitting laser that is a photonic crystal surface emitting laser element according to the second embodiment. FIG. 14 is a schematic perspective view showing a part of the configuration of the photonic crystal layer included in the surface emitting laser of FIG.

  Referring to FIGS. 13 and 14 and FIGS. 1 and 2, surface emitting laser 1 in the second embodiment basically has the same configuration as surface emitting laser 1 in the first embodiment described above, It operates similarly and produces the same effect. However, the surface emitting laser 1 of the second embodiment is different from the first embodiment in the configuration of the photonic crystal layer.

That is, referring to FIGS. 13 and 14, hole 15C of photonic crystal layer 15 in surface emitting laser 1 of the second embodiment is filled with dielectric pillar 15E (dielectric layer) made of a dielectric. . As a result, in the surface emitting laser 1 according to the second embodiment, the refractive index inside the hole 15C is adjusted by adjusting the dielectric constant inside the hole 15C of the photonic crystal layer 15 to various values different from air. It is possible to control. As the dielectric which constitutes the dielectric column 15E, for example, SiO ₂ (silicon dioxide), _Si 3 _{N 4} (silicon nitride), _Al 2 _{O 3} (aluminum oxide; alumina), TiO ₂ (titanium oxide; titania) Etc. can be adopted.

  That is, the photonic crystal layer 15 as a two-dimensional diffraction grating has a low refractive index portion and a high refractive index portion having a refractive index higher than that of the low refractive index portion. The high refractive index portion is a base layer 15D made of a semiconductor, and the low refractive index portion is a dielectric pillar 15E disposed inside a hole 15C formed in the base layer 15D. As a modification of the present embodiment, instead of the dielectric pillar 15E made of a dielectric, a transparent material having conductivity and a light refractive index different from that of the base layer 15D, for example, ITO which is a transparent oxide A conductive transparent column made of (Indium Tin Oxide) or the like may be employed. That is, a transparent column having a light refractive index different from that of the base layer 15D can be disposed inside the hole 15C of the photonic crystal layer 15.

  Next, the manufacturing method of the surface emitting laser in Embodiment 2 is demonstrated. FIG. 15 is a flowchart showing an outline of a method of manufacturing the surface emitting laser according to the second embodiment. FIG. 16 is a schematic cross-sectional view for explaining the method for manufacturing the surface emitting laser according to the second embodiment. The surface-emitting laser 1 according to the second embodiment can be basically manufactured in the same manner as the surface-emitting laser according to the first embodiment, except that a step of forming the dielectric pillar 15E is added. This is different from Form 1.

That is, referring to FIG. 15, first, steps (S10) to (S60) are performed in the same manner as in the first embodiment. Thereafter, the step (S70) is performed in the same manner as in the step (S70) in the first embodiment up to the process immediately before the removal of the resist layer 99. Then, a recess filling step is performed as a step (S80) without removing the resist layer 99. In this step (S80), with reference to FIG. 16, on the surface of the mask made of resist layer 99 is formed, for example, CVD; by (Chemical Vapor Deposition Chemical Vapor Deposition) method, SiO ₂ layer of SiO ₂ 98 is formed. Thus, the holes 15C are filled with the SiO ₂ layer 98. Thereafter, the SiO ₂ layer 98 on the resist layer 99 is removed together with the resist layer 99 (lift-off), whereby the surface emitting laser 1 in the second embodiment shown in FIG. 13 is completed.

  In the surface emitting laser 1 according to the second embodiment, since the distance between the photonic crystal layer 15 and the active layer 13 is sufficiently large, stress and strain generated when the photonic crystal layer 15 is formed are active. The effect on the layer 13 is reduced. Therefore, it is easy to adopt the photonic crystal layer 15 in which the dielectric pillar 15E is embedded, which is sometimes difficult to adopt in the conventional photonic crystal surface emitting laser element due to the strength of residual stress.

(Embodiment 3)
Next, Embodiment 3 which is still another embodiment of the present invention will be described. FIG. 17 is a schematic cross-sectional view showing a configuration of a surface emitting laser which is a photonic crystal surface emitting laser element in the third embodiment. FIG. 18 is a schematic plan view showing the configuration of the n-type back electrode side in the surface emitting laser of FIG. FIG. 19 is a schematic plan view showing the configuration of the p-type surface electrode side in the surface emitting laser of FIG.

  Referring to FIGS. 17 to 19 and FIGS. 1 and 3, surface emitting laser 1 in the third embodiment basically has the same configuration as surface emitting laser 1 in the first embodiment described above. It operates similarly and produces the same effect. However, the surface emitting laser 1 of the third embodiment differs from that of the first embodiment in the configuration of the p-type front electrode 16 and the n-type back electrode 17.

  That is, referring to FIGS. 17 to 19, p-type surface electrode 16 of surface-emitting laser 1 in the third embodiment penetrates p-type surface electrode 16 in the thickness direction, unlike in the first embodiment. The hole 16A is not formed. The p-type surface electrode 16 is formed so as to cover the entire region where the hole 15 </ b> C is formed in the photonic crystal layer 15. That is, the hole 15 </ b> C formed in the photonic crystal layer 15 is sealed by the p-type surface electrode 16.

  On the other hand, the n-type back electrode 17 is formed with a window portion 17A which is a through hole. The n-substrate 11 is exposed from the window portion 17A. This window portion 17A functions as an emission surface of surface emitting laser 1 in the third embodiment. That is, in the surface-emitting laser 1, light is emitted from the back surface side (the side on which the n-type back electrode 17 is formed) of the n− substrate 11 along the direction of the arrow α.

  Next, the manufacturing method of the surface emitting laser in Embodiment 3 is demonstrated. FIG. 20 is a flowchart showing an outline of a method for manufacturing the surface emitting laser according to the third embodiment. 21 to 24 are schematic cross-sectional views for explaining the method for manufacturing the surface emitting laser according to the third embodiment. The surface-emitting laser 1 according to the third embodiment can be manufactured basically in the same manner as the surface-emitting laser according to the first embodiment, but in the process of forming the p-type front electrode 16 and the n-type back electrode 17 This is different from Form 1.

  That is, referring to FIG. 20, first, steps (S10) to (S50) are performed in the same manner as in the first embodiment. Thereafter, in the electrode forming step performed as step (S60), referring to FIG. 21, p is formed so as to cover the region (see FIG. 17) where hole 15C is formed in second p-type semiconductor layer 92. A first p-type surface electrode 16 </ b> B is formed as a conductor layer constituting a part of the mold surface electrode 16. On the other hand, n-type back electrode 17 is formed on the main surface of n-substrate 11 opposite to the side on which n-cladding layer 12 is formed. A window portion 17A is formed in the n-type back electrode 17 in a region overlapping with a region (see FIG. 17) where the hole 15C is to be formed in plan view.

  Next, in step (S70), referring to FIG. 22, a resist layer 99 is formed by applying a resist on second p-type semiconductor layer 92 on which first p-type surface electrode 16B is formed. Thereafter, exposure and development are performed, so that an opening 99A corresponding to the desired shape and position of the hole 15C (see FIG. 17) is formed in the resist layer 99. Further, referring to FIG. 23, resist layer 99 in which opening 99A is formed is used as a mask, and, for example, dry etching is performed, thereby penetrating first p-type surface electrode 16B and second p-type semiconductor layer 92. And the air hole which reaches to the center of the thickness direction of the p-type semiconductor layer 91 is formed. Thereby, in the thickness direction of the p-type semiconductor layer 91, the region where the air holes are formed becomes the photonic crystal layer 15, and the region where the air holes are not formed becomes the p-cladding layer 14. Thereafter, referring to FIG. 24, resist layer 99 is removed.

  Next, with reference to FIG. 20, an electrode thickening process is implemented as process (S90). In this step (S90), the second p-type surface electrode 16C as another conductor layer constituting the p-type surface electrode 16 is formed on the first p-type surface electrode 16B. Specifically, referring to FIG. 24, another conductor is formed on the first p-type surface electrode 16B formed in step (S60) and through-holes are formed in step (S70) using, for example, a plating method. A second p-type surface electrode 16C as a layer is formed. Here, in this step (S90), referring to FIG. 17, the second p-type surface electrode 16C is grown in the lateral direction by using a plating method, so that the upper portion of the hole 15C formed in the photonic crystal layer 15 is obtained. Is closed by the second p-type surface electrode 16C. Through the above steps, the surface emitting laser 1 according to the third embodiment can be easily manufactured.

(Embodiment 4)
Next, a fourth embodiment which is still another embodiment of the present invention will be described. FIG. 25 is a schematic cross-sectional view showing a configuration of a surface emitting laser that is a photonic crystal surface emitting laser element according to the fourth embodiment.

  Referring to FIGS. 25 and 17, surface emitting laser 1 in the fourth embodiment basically has the same configuration as surface emitting laser 1 in the above-described third embodiment and operates in the same manner. The same effect is produced. However, the surface emitting laser 1 according to the fourth embodiment is different from the third embodiment in the configuration of the photonic crystal layer.

That is, referring to FIG. 25, hole 15C of photonic crystal layer 15 in surface-emitting laser 1 of Embodiment 4 is filled with dielectric pillar 15E (dielectric layer) made of a dielectric. Thereby, in the surface emitting laser 1 according to the fourth embodiment, the dielectric constant inside the hole 15C of the photonic crystal layer 15 can be controlled to various values different from air. For example, SiO ₂ , Si ₃ N ₄ , Al ₂ O ₃ , TiO _2, etc. can be used as the dielectric constituting the dielectric pillar 15E. Further, as a modification of the present embodiment, instead of the dielectric pillar 15E made of a dielectric, a transparent material having conductivity and a light refractive index different from that of the base layer 15D, for example, ITO which is a transparent oxide You may employ | adopt the electroconductive transparent body pillar which consists of these. That is, a transparent column having a light refractive index different from that of the base layer 15D can be disposed inside the hole 15C of the photonic crystal layer 15.

  Next, the manufacturing method of the surface emitting laser in Embodiment 4 is demonstrated. FIG. 26 is a flowchart showing an outline of a method of manufacturing the surface emitting laser according to the fourth embodiment. 27 and 28 are schematic cross-sectional views for describing the method for manufacturing the surface emitting laser according to the fourth embodiment. The surface-emitting laser 1 according to the fourth embodiment can be manufactured basically in the same manner as the surface-emitting laser according to the third embodiment, except that a step of forming the dielectric pillar 15E is added. This is different from the third form.

That is, referring to FIG. 26, first, steps (S10) to (S60) are performed in the same manner as in the third embodiment. Thereafter, in step (S70), the same process as in the step (S70) in the third embodiment up to the process immediately before the removal of resist layer 99 is performed. Then, a recess filling step is performed as a step (S80) without removing the resist layer 99. In this step (S80), with reference to FIG. 27, on the surface of the mask made of resist layer 99 is formed, for example, a CVD method, SiO ₂ layer 98 made of SiO ₂ is formed. Thereby, the holes 15 </ _b > C are filled with the SiO ₂ layer 98. Thereafter, the SiO ₂ layer 98 on the resist layer 99 is removed together with the resist layer 99 (lift-off), whereby the structure shown in FIG. 28 can be obtained. Then, the surface emitting laser 1 in the fourth embodiment is completed by performing the step (S90) in the same manner as in the third embodiment.

(Embodiment 5)
Next, Embodiment 5 which is still another embodiment of the present invention will be described. FIG. 29 is a schematic cross-sectional view showing a configuration of a surface emitting laser which is a photonic crystal surface emitting laser element in the fifth embodiment.

  29 and 17, surface emitting laser 1 in the fifth embodiment basically has the same configuration as surface emitting laser 1 in the above-described third embodiment, operates in the same manner, and The same effect is produced. However, the surface emitting laser 1 of the fifth embodiment is different from that of the third embodiment in the configuration of the photonic crystal layer and the p-type surface electrode.

  That is, referring to FIG. 29, hole 15C of photonic crystal layer 15 in surface-emitting laser 1 of the fifth embodiment has conductor column 15F (made of a conductor (for example, metal) constituting p-type surface electrode 16). It is filled with a conductor layer). That is, the photonic crystal layer 15 as a two-dimensional diffraction grating has a low refractive index portion and a high refractive index portion having a refractive index higher than that of the low refractive index portion. The high refractive index portion is made of a metal constituting the conductor column 15F, and the low refractive index portion is a base layer of the photonic crystal layer 15 made of a semiconductor.

  Next, a method for manufacturing the surface emitting laser according to the fifth embodiment will be described. FIG. 30 is a flowchart showing an outline of the method for manufacturing the surface emitting laser according to the fifth embodiment. 31 to 33 are schematic cross-sectional views for explaining the method for manufacturing the surface emitting laser according to the fifth embodiment. The surface-emitting laser 1 in the fifth embodiment can be manufactured basically in the same manner as the surface-emitting laser in the third embodiment, but in the step of forming the photonic crystal layer and the p-type surface electrode, This is different from Form 3.

  That is, referring to FIG. 30, first, steps (S10) to (S50) are performed in the same manner as in the third embodiment. Thereafter, a back electrode forming step is performed as a step (S61). In this step (S61), in the step (S60) in the third embodiment, the step of forming the n-type back electrode 17 is performed in the same manner as in the third embodiment, and the structure shown in FIG. 31 is obtained. .

  Next, a recess forming step is performed as a step (S70). In this step (S70), referring to FIG. 32, a mask made of resist layer 99 in which opening 99A is formed is formed. Thereafter, similarly to the case of the third embodiment, for example, dry etching is performed to form the hole 15C. Thereafter, as shown in FIG. 33, resist layer 99 is removed.

  Next, a surface electrode forming step is performed as a step (S100). In this step (S100), referring to FIG. 29, the p-type surface electrode extends from the inside of hole 15C formed in step (S70) to the upper surface of contact layer 15B constituting the base layer. 16 is formed. Thereby, the holes 15C formed in the step (S70) are filled with the conductor columns 15F. Through the above steps, the surface emitting laser 1 according to the fifth embodiment can be easily manufactured.

  Embodiment 1 of the present invention will be described below. A laser element having the same configuration as that of the surface emitting laser 1 in the third embodiment was manufactured, and an experiment for confirming the operation state was performed. The experimental procedure is as follows.

  First, a surface light emitting device having the same configuration as that of the third embodiment was manufactured. Specifically, first, a lattice-matched n-AlGaAsSb cladding layer having a thickness of 3 μm, an active layer, a lattice-matching p-AlGaAsSb cladding layer having a thickness of 1 μm, and a p-AlGaAsSb having a thickness of 1.1 μm on an n-GaSb substrate (001) surface. Surface light emission in which a photonic crystal layer composed of a main layer and a p-GaSb contact layer, a rectangular p-type surface electrode is formed, and an n-type back electrode having a window portion is formed on the main surface opposite to the n-GaSb substrate A laser was prepared. Here, the active layer has an MQW (multiple quantum well) structure having a repeating structure of an undoped AlGaSb barrier layer and an undoped InGaAsSb well layer. The composition of the barrier layer is Al (0.3) Ga (0.7) Sb, and the composition of the well layer is In (0.4) Ga (0.6) As (0.15) Sb (0.85). did. The composition of the lattice matched n-cladding layer and the p-cladding layer was Al (0.9) Ga (0.1) As (0.05) Sb (0.95). Furthermore, the photonic crystal layer employs a structure in which air holes are arranged in a triangular lattice shape, the lattice constant is 0.74 μm, and the air filling rate is 15% (the shape of the air holes has a bottom diameter of 300 nm). A cylindrical shape with a depth (height) of 1.1 μm The planar shape of the region where the holes are formed in the photonic crystal layer is a square shape with a side of 300 μm. It was the same as the case of.

Next, when an appropriate current was applied to the prepared laser element and observed from the back side, room temperature pulse oscillation was confirmed at a threshold current density of 200 A / cm ² . The oscillation wavelength was a single wavelength of 2.5 μm. When this oscillation state was observed with a far field image (FFP), it was found that the pattern was a donut-shaped pattern with a radiation angle of 1 degree in a direction perpendicular to the substrate surface, and it was a single mode.

In addition, when a laser element having a structure in which the hole of the photonic crystal layer is embedded with SiO ₂ (the same structure as in the fourth embodiment) is prepared and the same experiment is performed, the same oscillation characteristics are obtained. was gotten.

  Embodiment 2 of the present invention will be described below. A laser element having the same configuration as that of the surface emitting laser 1 in the fifth embodiment was manufactured, and an experiment for confirming the operation state was performed. The experimental procedure is as follows.

  First, a surface light emitting device having the same configuration as that of the fifth embodiment was manufactured. Specifically, first, on a n-InAs substrate (001) surface, a lattice matching n-AlAsSb cladding layer having a thickness of 3 μm, an active layer, a lattice matching p-AlAsSb cladding layer having a thickness of 1 μm, and a p-AlAsSb layer having a thickness of 1.1 μm. Surface light emission in which a photonic crystal layer composed of a main layer and a p-InAs contact layer, a rectangular p-type surface electrode is formed, and an n-type back electrode having a window portion is formed on the main surface opposite to the n-InAs substrate A laser was prepared. Here, the active layer has an MQW (multiple quantum well) structure having a repeating structure of an undoped InAs barrier layer and an undoped InAsSb well layer. The composition of the well layer was InAs (0.9) Sb (0.1). The composition of the lattice matched n-cladding layer and p-cladding layer was AlAs (0.15) Sb (0.85). Furthermore, the photonic crystal layer adopts a structure in which the holes are arranged in a triangular lattice shape, the lattice constant is 1.3 μm, the air filling rate is 15% (the shape of the air holes is a cylindrical shape with a diameter of 530 nm on the bottom surface, The depth (height) was 1.1 μm, and this hole was filled with the metal constituting the p-type surface electrode.The planar shape of the region where the hole was formed in the photonic crystal layer was a square having a side of 400 μm. The manufacturing process was the same as in the case of the fifth embodiment.

Next, when an appropriate current was applied to the prepared laser element and observed from the back side, room temperature pulse oscillation was confirmed at a threshold current density of 450 A / cm ² . The oscillation wavelength was a single wavelength of 3.8 μm. When this oscillation state was observed with a far field image (FFP), it was found that the pattern was a donut-shaped pattern with a radiation angle of 1 degree in a direction perpendicular to the substrate surface, and it was a single mode.

  From the experimental results in the above examples, it was confirmed that the photonic crystal surface emitting laser element of the present invention can oscillate at room temperature while simplifying the manufacturing process.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The photonic crystal surface emitting laser element and the manufacturing method thereof according to the present invention are particularly advantageously applied to a photonic crystal surface emitting laser element and a manufacturing method thereof that require a simplified manufacturing process.

2 is a schematic cross-sectional view showing a configuration of a surface emitting laser according to Embodiment 1. FIG. It is a schematic perspective view which shows a part of structure of the photonic crystal layer contained in the surface emitting laser of FIG. It is a schematic plan view which shows the structure of the p-type surface electrode with which the surface emitting laser of FIG. 1 is provided. It is a figure for demonstrating the diffraction of the light in a triangular lattice. It is a schematic perspective view which shows the other structure of a photonic crystal layer. It is a figure for demonstrating the diffraction of the light in a square lattice. 3 is a flowchart showing an outline of a method for manufacturing a photonic crystal surface emitting laser element in the first embodiment. FIG. 5 is a schematic cross-sectional view for illustrating the method for manufacturing the photonic crystal surface emitting laser element in the first embodiment. FIG. 5 is a schematic cross-sectional view for illustrating the method for manufacturing the photonic crystal surface emitting laser element in the first embodiment. FIG. 5 is a schematic cross-sectional view for illustrating the method for manufacturing the photonic crystal surface emitting laser element in the first embodiment. FIG. 5 is a schematic cross-sectional view for illustrating the method for manufacturing the photonic crystal surface emitting laser element in the first embodiment. FIG. 5 is a schematic cross-sectional view for illustrating the method for manufacturing the photonic crystal surface emitting laser element in the first embodiment. 6 is a schematic cross-sectional view showing a configuration of a surface emitting laser according to Embodiment 2. FIG. It is a schematic perspective view which shows a part of structure of the photonic crystal layer contained in the surface emitting laser of FIG. 5 is a flowchart showing an outline of a method for manufacturing a surface emitting laser according to a second embodiment. FIG. 10 is a schematic cross-sectional view for illustrating the method for manufacturing the surface emitting laser in the second embodiment. 6 is a schematic cross-sectional view showing a configuration of a surface emitting laser according to Embodiment 3. FIG. It is a schematic plan view which shows the structure by the side of the n-type back surface electrode in the surface emitting laser of FIG. It is a schematic plan view which shows the structure by the side of the p-type surface electrode in the surface emitting laser of FIG. 10 is a flowchart showing an outline of a method for manufacturing a surface emitting laser according to a third embodiment. FIG. 10 is a schematic cross-sectional view for illustrating the method for manufacturing the surface emitting laser in the third embodiment. FIG. 10 is a schematic cross-sectional view for illustrating the method for manufacturing the surface emitting laser in the third embodiment. FIG. 10 is a schematic cross-sectional view for illustrating the method for manufacturing the surface emitting laser in the third embodiment. FIG. 10 is a schematic cross-sectional view for illustrating the method for manufacturing the surface emitting laser in the third embodiment. 6 is a schematic cross-sectional view showing a configuration of a surface emitting laser according to Embodiment 4. FIG. 6 is a flowchart showing an outline of a method for manufacturing a surface emitting laser according to a fourth embodiment. FIG. 10 is a schematic cross-sectional view for illustrating the method for manufacturing the surface emitting laser in the fourth embodiment. FIG. 10 is a schematic cross-sectional view for illustrating the method for manufacturing the surface emitting laser in the fourth embodiment. FIG. 10 is a schematic cross-sectional view showing a configuration of a surface emitting laser in a fifth embodiment. 10 is a flowchart showing an outline of a method for manufacturing a surface emitting laser according to a fifth embodiment. FIG. 10 is a schematic cross-sectional view for illustrating the method for manufacturing the surface emitting laser in the fifth embodiment. FIG. 10 is a schematic cross-sectional view for illustrating the method for manufacturing the surface emitting laser in the fifth embodiment. FIG. 10 is a schematic cross-sectional view for illustrating the method for manufacturing the surface emitting laser in the fifth embodiment.

Explanation of symbols

1 surface emitting laser, 11 n-substrate, 12 n-clad layer, 13 active layer, 14 p-clad layer, 15 photonic crystal layer, 15A main layer, 15B contact layer, 15C hole, 15D base layer, 15E dielectric Pillar, 15F conductor pillar, 16 p-type surface electrode, 16A hole, 16B first p-type surface electrode, 16C second p-type surface electrode, 17 n-type back electrode, 17A window, 91 p-type semiconductor layer, 92 second p-type Semiconductor layer, 98 SiO ₂ layer, 99 resist layer, 99A opening.

Claims (1)

An active layer,
A semiconductor layer disposed so as to sandwich the active layer;
A two-dimensional diffraction grating formed on the surface of the semiconductor layer and independent of the active layer;
An electrode formed in contact with the entire two-dimensional diffraction grating,
The two-dimensional diffraction grating functions alone as an optical resonator,
The two-dimensional diffraction grating has a low refractive index portion and a high refractive index portion having a refractive index higher than the refractive index of the low refractive index portion,
The high refractive index portion is made of a semiconductor,
The low refractive index moiety, Ri hole der formed in the high refractive index portion,
The wavelength of light emitted from the active layer that has become in the range of 1.5μm or more 8μm or less, photonic crystal surface-emitting laser element.

Images