JP2007221023A - Surface-emitting laser element, optical transmission module including the element, and optical transmission system including the module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface emitting laser element to be operated by low-threshold current and in a single mode. <P>SOLUTION: A surface emitting laser element 100 has a structure obtained by successively laminating the following layers on a substrate 101, i.e., a reflection layer 102, a resonator spacer layer 103, an active layer 104, a resonator spacer layer 105, a superlattice structure film 106, and a reflection layer 107. High resistance layers 108A, 108B are formed in the reflection layer 107. A p-side electrode 109 is formed in a part of the reflection layer 107 excluding an outgoing port 107A. An n-side electrode 110 is formed on the rear surface of the substrate 101. The superlattice structure film 106 is arranged in a region other than the active layer 104 and the reflection layers 102, 107; and includes regions 106A, 106B, 106C. The regions 106A, 106C are composed of the disordered superlattice structure film. The region 106B is composed of the ordered superlattice structure film. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a surface emitting laser device, an optical transmission module including the same, and an optical transmission system including the same.

  In recent years, optical transmission technology has been developed not only in trunk transmission networks but also in LANs (Local Area Networks), optical access systems, and home networks. A resonator type surface emitting laser element has been used as a light source for LAN or optical interconnection.

  Cavity type surface emitting laser elements have lower power consumption than conventional end facet type semiconductor lasers, require no cleaving in the manufacturing process, and can be inspected in the wafer state. It has excellent characteristics.

  The cavity surface emitting laser element is operated with a low threshold current by confining the current in a narrow region of the active layer. Further, in order to stabilize the transverse mode of light, a structure for confining light is used. As an optical confinement structure in the cavity surface emitting laser element, an air post structure, a buried structure, a selective oxidation structure, a side etching structure, a disordered structure, and the like have been proposed so far.

  In the air post structure and the buried structure, since a recombination current flows on the side surface of the active layer, it is difficult to reduce the threshold current. Further, the selective oxidation structure and the side etching structure are structurally fragile, and cracks may occur to deteriorate the device.

  On the other hand, as a cavity surface emitting laser element using a disordered structure, a structure in which an active layer including a superlattice is disordered and current is confined by increasing a band gap (Patent Documents 1 and 2), and a surface A structure (Patent Documents 3 and 4) in which light is confined by forming an effective refractive index difference in the lateral direction by disordering a part of the multilayer mirror of the light emitting laser element is proposed.

In the structures disclosed in Patent Documents 1 and 2, the disordered region has a function of confining light at the same time because the refractive index decreases.
JP-A-9-260778 JP-A-9-205250 Japanese Patent No. 3546630 Japanese Patent Laid-Open No. 9-051145

  However, in the structures disclosed in Patent Documents 1 and 2, since the active layer is disordered, the defect density in the active layer increases, and the reactive current that does not contribute to light emission increases. As a result, there is a problem that the threshold current for laser oscillation increases.

  In the structures disclosed in Patent Documents 3 and 4, when a part of the multilayer reflector is disordered and the periodicity is lost, the reflectance of the multilayer reflector is reduced. As a result, the effective refractive index difference is greatly different between the disordered region and the non-disordered region, and a high-order transverse mode is likely to occur. Therefore, in order to operate in a single mode, the constriction area must be narrowed, and it is difficult to form a surface emitting laser element.

  Accordingly, the present invention has been made to solve such a problem, and an object of the present invention is to provide a surface emitting laser element which can operate in a single mode with a low threshold current.

  Another object of the present invention is to provide an optical transmission module including a surface emitting laser element that can operate in a single mode with a low threshold current.

  Furthermore, another object of the present invention is to provide an optical transmission system including a surface emitting laser element that can operate in a single mode with a low threshold current.

  According to this invention, the surface emitting laser element includes an active layer, a resonator spacer layer, a reflective layer, a current injection layer, and an optical layer. The resonator spacer layer is provided on both sides of the active layer. The reflection layers are provided on both sides of the resonator spacer layer, and reflect the oscillation light oscillated in the active layer. The current injection layer injects a current into the active layer while limiting a region through which the current passes. The optical layer is provided in a region other than the active layer and the reflective layer, and confines the oscillating light in a current passing region through which the current injected into the active layer passes in the in-plane direction substantially perpendicular to the emitting direction of the oscillating light. The oscillated light passes through the exit. Then, the optical layer confines the oscillation light in the current passing region using the disordered superlattice structure film.

  Preferably, the optical layer includes first and second superlattice structure films. The first superlattice structure film is provided in the current passage region and is ordered. The second superlattice structure film is provided outside the first superlattice structure film in the in-plane direction and is disordered.

  Preferably, each of the first and second superlattice structure films has a band gap larger than the band gap of the active layer.

  Preferably, the optical layer is provided on the exit side of the active layer.

  Preferably, the resonator spacer layer is composed of first and second resonator spacer layers. The first resonator spacer layer is provided on the side opposite to the emission port with respect to the active layer. The second resonator spacer layer is provided closer to the emission port than the active layer. The reflective layer is composed of first and second reflective layers. The first reflective layer is provided on the side opposite to the emission port with respect to the active layer. The second reflective layer is provided closer to the emission port than the active layer. The optical layer is provided between the second resonator spacer layer and the second reflective layer.

  Preferably, the current injection layer is provided closer to the emission port than the active layer.

  Preferably, the current injection layer is provided in the second reflective layer.

  Preferably, the current injection layer includes a current passage layer and a current confinement layer. The current passage layer has the same resistance as the second reflective layer. The current confinement layer is provided outside the current passage layer in the in-plane direction and has a larger resistance than the current passage layer.

  Preferably, the current injection layer is provided between the optical layer and the second reflective layer.

  Preferably, the current injection layer is provided in contact with the optical layer.

  Preferably, the current injection layer includes a current passage layer and a current confinement layer. The current passing layer allows a current to pass through the active layer through a tunnel junction. The current confinement layer is provided outside the current passage layer in the in-plane direction, and restricts the passage of current to the active layer by pn reverse junction.

  Preferably, the current injection layer and the pre-study layer are provided on opposite sides of the active layer.

  Preferably, the current injection layer and the optical layer are provided in the resonator spacer layer.

  Preferably, the resonator spacer layer is composed of first and second resonator spacer layers. The first resonator spacer layer is provided on the side opposite to the emission port with respect to the active layer. The second resonator spacer layer is provided closer to the emission port than the active layer. The current injection layer is provided in the first resonator spacer layer. The optical layer is provided in the second resonator spacer layer.

  Preferably, the current injection layer includes a current passage layer and a current confinement layer. The current passing layer allows a current to pass through the active layer through a tunnel junction. The current confinement layer is provided outside the current passage layer in the in-plane direction, and restricts the passage of current to the active layer by pn reverse junction.

  Preferably, the area of the current passage layer is larger than the area of the first superlattice structure film.

  Preferably, the second superlattice structure film includes an electrically inactive element or a crystal constituent element.

  Preferably, the sum of the thickness of the active layer and the thickness of the resonator spacer layer is longer than one wavelength of oscillation light.

  Preferably, the active layer includes both a nitrogen element and a group V element other than the nitrogen element.

  Moreover, according to this invention, an optical transmission module is an optical transmission module provided with the surface emitting laser element of any one of Claims 1-19.

  Furthermore, according to this invention, an optical transmission system is an optical transmission system comprising the optical transmission module according to claim 20.

  In the surface emitting laser device according to the present invention, the optical layer that confines the oscillation light in the current passing region using the disordered superlattice structure film is provided in a region other than the active layer and the reflective layer. While current is suppressed, a decrease in reflectance in the reflective layer is suppressed.

  Therefore, according to the present invention, the surface emitting laser element can be operated in a single mode with a low threshold current.

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

[Embodiment 1]
FIG. 1 is a schematic sectional view of a surface emitting laser element according to Embodiment 1 of the present invention. Referring to FIG. 1, a surface emitting laser element 100 according to Embodiment 1 of the present invention includes a substrate 101, reflection layers 102 and 107, resonator spacer layers 103 and 105, an active layer 104, and a superlattice structure. A film 106, high resistance layers 108A and 108B, a p-side electrode 109, and an n-side electrode 110 are provided. The surface emitting laser element 100 is a surface emitting laser element having a wavelength of oscillation light of 850 nm.

The substrate 101 is made of n-type gallium arsenide (n-GaAs). The reflective layer 102 has [n-Al _0.9 Ga of 40.5 periods when a pair of n-Al _0.9 Ga _0.1 As / n-Al _0.2 Ga _0.8 As is taken as one period. _0.1 As / n-Al _0.2 Ga _0.8 As] and is formed on one main surface of the substrate 101. _Each of the _n-Al 0.9 _{Ga 0.1} As and _n-Al 0.2 _{Ga 0.8} As, when the wavelength of the oscillation light (850 nm) was _{λ 1, λ 1 / 4n (} n is The refractive index of the semiconductor layer).

The resonator spacer layer 103 is made of non-doped Al _0.2 Ga _0.8 As and is formed on the reflective layer 102. The active layer 104 has a multiple quantum well structure composed of [GaAs / Al _0.4 Ga _0.6 As] having three periods when a pair of GaAs / Al _0.4 Ga _0.6 As is defined as one period. , Formed on the resonator spacer layer 103. GaAs has a thickness of 6 nm, and Al _0.4 Ga _0.6 As has a thickness of 8 nm.

The resonator spacer layer 105 is made of non-doped Al _0.2 Ga _0.8 As and is formed on the active layer 104. The superlattice structure film 106 has four periods of [Al _0.2 Ga _0.8 As / Al when a pair of Al _0.2 Ga _0.8 As / Al _0.4 Ga _0.6 As is taken as one period. _0.4 Ga _0.6 As] and formed on the resonator spacer layer 105. Each of Al _0.2 Ga _0.8 As and Al _0.4 Ga _0.6 As has a thickness of 4 nm.

Superlattice structure film 106 includes disordered regions 106A and 106C and ordered region 106B. Each of the regions 106A and 106C is formed of a superlattice structure film of [Al _0.2 Ga _0.8 As / Al _0.4 Ga _0.6 As] containing zinc (Zn), and the region 106B contains Zn. It consists of a superlattice structure film of [Al _0.2 Ga _0.8 As / Al _0.4 Ga _0.6 As]. Each of the regions 106A and 106C has a refractive index lower than that of the region 106B. The region 106B has a length of 4 μm in the in-plane direction DR2 substantially perpendicular to the emission direction DR1 of the oscillation light.

The reflective layer 107 has 26 periods [p-Al _0.9 Ga _{0 .0} when a pair of p-Al _0.9 Ga _0.1 As / p-Al _0.2 Ga _0.8 As is taken as one period _{. 1} As / p-Al _0.2 Ga _0.8 As] and is formed on the superlattice structure film 106. Each of p-Al _0.9 Ga _0.1 As and p-Al _0.2 Ga _0.8 As has a film thickness of λ ₁ / 4n (n is the refractive index of the semiconductor layer).

The high resistance layers 108 _< / b> A and 108 _< / b> B are formed in the reflective layer 107, and have a periodic structure of [p-Al _0.9 Ga _0.1 As / p-Al _0.2 Ga _0.8 As] with protons (H ⁺ ). It consists of the structure which inject | poured. The region 108C sandwiched between the high resistance layers 108A and 108B has a length of 4 μm in the in-plane direction DR2.

  The p-side electrode 109 is formed on a part of the reflective layer 107 excluding the emission port 107A. The n-side electrode 110 is formed on the back surface of the substrate 101.

  Each of the reflective layers 102 and 107 constitutes a semiconductor distributed Bragg reflector that reflects the oscillation light oscillated in the active layer 104 by Bragg multiple reflection and confines it in the active layer 104. The distance between the reflective layer 102 and the reflective layer 107 is an optical length corresponding to one wavelength of the oscillation wavelength (= 850 nm), and the resonator spacer layers 103 and 105 sandwiched between the reflective layers 102 and 107, the active layer The layer 104 and the superlattice structure film 106 constitute a resonator.

  The superlattice structure film 106 is formed in a region other than the reflective layers 102 and 107 and the active layer 104 on the exit 107A side of the active layer 104. In the superlattice structure film 106, each of the disordered regions 106A and 106C has a refractive index lower than the refractive index of the ordered region 106B. The oscillated oscillated light is confined in the region 106B by the regions 106A and 106C, and the oscillated light is passed through the region 106B in the direction of the emission port 107A. Thereby, the transverse mode of the surface emitting laser element 100 is stabilized. That is, in the surface emitting laser element 100, the higher-order oscillation mode is suppressed, and oscillation light consisting of only a single fundamental oscillation mode is emitted.

The superlattice structure film 106 has a periodic structure of [Al _0.2 Ga _0.8 As / Al _0.4 Ga _0.6 As], and the active layer 104 has [GaAs / Al _0.4 Ga _{0. .6} As], the superlattice structure film 106 has a larger band gap than the band gap of the active layer 104. Therefore, the superlattice structure film 106 does not absorb the oscillation light oscillated in the active layer 104 and forms a waveguide structure with low loss.

  Since the high resistance layers 108A and 108B have a resistance higher than that of the reflective layer 107, the current injected from the p-side electrode 109 is prevented from flowing toward the active layer 104, and the region through which the current passes is defined as the region 108C. Limit to.

  2, 3 and 4 are first to third process diagrams showing a method for manufacturing the surface-emitting laser element 100 shown in FIG. 1, respectively. Referring to FIG. 2, when a series of operations is started, a reflective layer 102, a resonator spacer layer 103, an active layer 104, a resonance layer are formed using metal organic chemical vapor deposition (MOCVD). A container spacer layer 105 and a superlattice structure film 106 are sequentially stacked on the substrate 101 (see step (a) in FIG. 2).

In this case, n-Al _0.9 Ga _0.1 As and n-Al _0.2 Ga _0.8 As of the reflective layer 102 are changed to trimethylaluminum (TMA), trimethylgallium (TMG), arsine (AsH ₃ ), and selenium. Hydrogen fluoride (H ₂ Se) is formed as a raw material.

Further, non-doped Al _0.2 Ga _0.8 As for the resonator spacer layer 103 is formed using trimethyl aluminum (TMA), trimethyl gallium (TMG), and arsine (AsH ₃ ) as raw materials, and the GaAs / Al _{0 of the} active layer 104 is formed. _.4 Ga _0.6 As is formed using trimethylaluminum (TMA), trimethylgallium (TMG) and arsine (AsH ₃ ) as raw materials.

Further, non-doped Al _0.2 Ga _0.8 As for the resonator spacer layer 105 is formed using trimethylaluminum (TMA), trimethylgallium (TMG), and arsine (AsH ₃ ) as raw materials, and Al _{0 of the} superlattice structure film 106 is formed. _.2 Ga _0.8 As and Al _0.4 Ga _0.6 As are formed using trimethylaluminum (TMA), trimethylgallium (TMG) and arsine (AsH ₃ ) as raw materials.

  Thereafter, a silicon nitride (SiN) film 120 is formed on the superlattice structure film 106, and a patterned resist pattern 130 is formed on the formed SiN film 120 (see step (b) in FIG. 2). In this case, the resist pattern 130 has a circular shape with a diameter of 4 μm.

  When the resist pattern 130 is formed, the SiN film 120 is removed by etching using the formed resist pattern 130 as a mask, and the resist pattern 130 is further removed (see step (c) in FIG. 2). Thereby, the SiN film 121 is formed on the superlattice structure film 106.

  Then, a zinc oxide (ZnO) film 140 is formed on the superlattice structure film 106 and the SiN film 121 by vapor deposition, and then heat-treated at 600 ° C. to thermally diffuse Zn into the superlattice structure film 106 (FIG. 2). (See (d)).

  Next, referring to FIG. 3, when the heat treatment is completed in step (d) shown in FIG. 2 and the SiN film 121 and the ZnO film 140 are removed by etching, the disordered regions 106A and 106C are ordered. A region 106B is formed in the superlattice structure film 106 (see FIG. 3E).

Thereafter, the reflective layer 107 is formed on the superlattice structure film 106 by MOCVD (see FIG. 3F). In this case, p-Al _0.9 Ga _0.1 As and p-Al _0.2 Ga _0.8 As of the reflective layer 107 are trimethylaluminum (TMA), trimethylgallium (TMG), arsine (AsH ₃ ) and four. Carbon bromide (CBr ₄ ) is used as a raw material.

  Then, a SiN film 150 is formed on the reflective layer 107, and a patterned resist pattern 160 is formed on the formed SiN film 150 (see step (g) in FIG. 3). In this case, the resist pattern 160 has a circular shape with a diameter of 4 μm.

  When the resist pattern 160 is formed, the SiN film 150 is removed by etching using the formed resist pattern 160 as a mask, and the resist pattern 160 is further removed. Thereby, the SiN film 151 is formed on the reflective layer 107 (see step (h) in FIG. 4).

Then, using the SiN film 151 as a mask, H ⁺ is implanted to form high resistance layers 108A and 108B in the reflective layer 107 (see (i) of FIG. 4). Then, SiN 151 is removed by etching, a p-side electrode 109 is formed on a part of the reflective layer 107 by vapor deposition and lift-off, and an n-side electrode 110 is formed on the back surface of the substrate 101 by vapor deposition ((j in FIG. 4). )reference). Thereby, the surface emitting laser element 100 is completed.

  When the surface emitting laser element 100 is oscillated, lead wires are connected to the p-side electrode 109 and the n-side electrode 110, and current is injected from the p-side electrode 109. Then, in the surface emitting laser element 100, the high resistance layers 108 </ b> A and 108 </ b> B limit the current passing region injected from the p-side electrode 109 to the region 108 </ b> C and inject current into the active layer 104.

  When the current injected into the active layer 104 reaches the threshold current, oscillation light is generated in the active layer 104, and the generated oscillation light is reflected by the reflection layers 102 and 107. Further, the regions 106A and 106C of the superlattice structure film 106 confine the oscillation light in the region 106B. As a result, the oscillation light oscillates in a single mode and is radiated from the emission port 107A.

  As described above, in the surface-emitting laser element 100, the layer formed of the high resistance layers 108A and 108B and the region 108C limits the current injection region to the region 108C by the high resistance layers 108A and 108B, and causes the current to flow into the active layer 104. The superlattice structure film 106 confins the oscillation light oscillated in the active layer 104 in the region 106B by the regions 106A and 106C. Since the disordered regions 106A and 106C are formed in regions other than the active layer 104 and the reflective layers 102 and 107, an increase in defect density in the active layer 104 is suppressed. Therefore, the surface emitting laser element 100 can oscillate single mode oscillation light with a low threshold current.

  In the above description, it has been described that Zn is thermally diffused into the superlattice structure film 106 to form the disordered regions 106A and 106C of the superlattice structure film 106. However, the present invention is not limited to this. More than electrically inactive elements such as argon (Ar) and krypton (Kr) or crystalline constituent elements such as gallium (Ga), aluminum (Al), indium (In), arsenic (As) and phosphorus (P) The disordered regions 106A and 106C may be formed by ion implantation into the lattice structure film 106 and subsequent annealing.

  In this case, since the ion-implanted element does not function as an acceptor and a donor, the carrier concentration in the disordered regions 106A and 106C is not increased. As a result, the light absorption loss due to free carriers does not increase in the disordered regions 106A and 106C. Therefore, the slope efficiency of the surface emitting laser element 100 is not lowered, and a highly efficient surface emitting laser element can be manufactured. The slope efficiency refers to the rate at which the intensity of the oscillating light changes with respect to the injected current in a graph in which the injected current is taken on the horizontal axis and the intensity of the oscillated light is taken on the vertical axis.

  In the above description, the interval between the reflective layer 102 and the reflective layer 107 has been described as being set to one wavelength of the oscillation wavelength (= 850 nm). However, the present invention is not limited to this, and the reflective layer 102 is not limited thereto. The distance between the reflective layer 107 and the reflective layer 107 may be set longer than one wavelength of the oscillation wavelength (= 850 nm).

  In the surface emitting laser element 100, in order for the active layer 104 to be positioned at the antinode of the optical standing wave and phase-matched, a resonator including the resonator spacer layers 103 and 105, the active layer 104, and the superlattice structure film 106 is used. (Length in the direction DR1) must be set to ½ times natural number times the optical distance of the oscillation wavelength (= 850 nm). For this reason, in the surface emitting laser element 100, the length of the resonator is normally set to one time the optical distance of the oscillation wavelength (= 850 nm).

  However, since the length of the resonator only needs to be set to a half of the optical distance of the oscillation wavelength (= 850 nm) × natural number times, the length of the resonator is the optical wavelength of the oscillation wavelength (= 850 nm). You may set the distance longer than 1 time of distance. As a result, the superlattice structure film 106 can be moved away from the active layer 104 in the resonator. When the superlattice structure is disordered by thermal diffusion or ion implantation, the active layer 104 is not disordered. The reactive current in the active layer 104 is suppressed, and the surface emitting laser element 100 can be operated with a low threshold current.

Further, in the above description, the active layer 104 has been described as having a multiple quantum well structure of GaAs / Al _0.4 Ga _0.6 As. However, in the present invention, the present invention is not limited to this, and the active layer 104 includes nitrogen ( N) and a mixed crystal semiconductor containing a group V element other than nitrogen (N) may be used.

  Mixed crystal semiconductors containing N and Group V elements other than N include GaNAs, GaInNAs, AlGaNAs, AlGaInNAs, GaNAsP, GaInNAsP, AlGaAsP, AlGaInNAsP, GaNAsSb, GaInNAsSb, AlGaNAsSb, AlGaInNAsSb, GaAlNAPSPS, GaAlNAPSPS, and GaInGaNPS. .

  A mixed crystal semiconductor containing N and a group V element other than N has a band gap of a long wavelength band of 1.3 to 1.6 μm suitable for transmission through a quartz optical fiber, and is a barrier made of GaAs or the like. Since the barrier height when electrons in the conduction band are confined in the well layer between the layers can be increased, overflow of electrons from the active layer 104 is suppressed, and N and V group elements other than N are included. The surface emitting laser element 100 using a mixed crystal semiconductor for the active layer 104 has good temperature characteristics.

  Further, since a mixed crystal semiconductor containing N and a group V element other than N can be epitaxially grown on the GaAs substrate, a surface using a mixed crystal semiconductor containing a group V element other than N and N as the active layer 104 is used. In the light emitting laser element, a GaAs / AlGaAs-based reflective layer having high reflectivity and excellent thermal conductivity can be used as the multilayer mirror. Therefore, a high-performance long-wavelength surface emitting laser element can be manufactured.

  The superlattice structure film 106 constitutes an “optical layer”, the ordered region 106B constitutes a “light passage layer”, and the disordered regions 106A and 106C constitute “light confinement layers”. Configure.

  Further, the ordered region 106B constitutes a “first superlattice structure film”, and the disordered regions 106A and 106C constitute a “second superlattice structure film”.

  Further, the high resistance layers 108A and 108B and the region 108C constitute a “current injection layer”, the regions 108A and 108B constitute a “current confinement layer”, and the region 108C constitutes a “current passing layer”.

  Further, the resonator spacer 103 constitutes a “first resonator spacer layer”, and the resonator spacer 105 constitutes a “second resonator spacer layer”.

  Further, the reflective layer 102 constitutes a “first reflective layer”, and the reflective element 107 constitutes a “second reflective layer”.

[Embodiment 2]
FIG. 5 is a schematic sectional view of the surface emitting laser element according to the second embodiment. Referring to FIG. 5, the surface emitting laser element 100A according to the second embodiment includes a substrate 201, reflection layers 202 and 208, resonator spacer layers 203 and 205, an active layer 204, a superlattice structure film 206, and the like. , A tunnel junction layer 207, a p-side electrode 209, and an n-side electrode 210. The surface emitting laser element 100A, the wavelength lambda ₂ of the oscillation light is a surface-emitting laser element is 980 nm.

The substrate 201 is made of n-GaAs. The reflective layer 202 has [n-GaAs / n-Al _0.9 Ga _0.1 As of 40.5 periods when a pair of n-GaAs / n-Al _0.9 Ga _0.1 As is taken as one period. And is formed on one main surface of the substrate 201. Each of n-GaAs and n-Al _0.9 Ga _0.1 As has a film thickness of λ ₂ / 4n (n is the refractive index of the semiconductor layer).

  The resonator spacer layer 203 is made of n-GaAs and is formed on the reflective layer 202. The active layer 204 has a multi-quantum well structure composed of [GaInAs / GaAs] with three periods when a pair of GaInAs / GaAs is taken as one period, and is formed on the resonator spacer layer 203. GaInAs has a thickness of 8 nm, and GaAs has a thickness of 10 nm.

The resonator spacer layer 205 is made of p-GaAs and is formed on the active layer 204. The superlattice structure film 206 has four periods [p-GaAs / p-Al _0.4 Ga _0.6 As when a pair of p-GaAs / p-Al _0.4 Ga _0.6 As is taken as one period. And is formed on the resonator spacer layer 205. Each of p-GaAs and p-Al _0.4 Ga _0.6 As has a thickness of 4 nm.

The superlattice structure film 206 includes disordered regions 206A and 206C and an ordered region 206B. Region 206A, each 206C consists superlattice structure membrane was implanted Ga ions _{[p-GaAs / p-Al} 0.4 Ga 0.6 As], region 206B is not implanted Ga ions [ consisting superlattice structure layer of _{p-GaAs / p-Al 0.4} Ga 0.6 As]. Each of the regions 206A and 206C has a refractive index lower than that of the region 206B. The region 206B has a length of 4 μm in the in-plane direction DR2.

The tunnel junction layer 207 is made of p-type highly doped GaAs (p ⁺ -GaAs) / n-type highly doped GaAs (n ⁺ -GaAs), and is formed on the superlattice structure film 206. In this ^case, p + -GaAs are formed in super lattice structure layer 206 side. Each film thickness of p ⁺ -GaAs and n ⁺ -GaAs is 10 nm, and p ⁺ -GaAs is doped with carbon (C) of 1 × 10 ²⁰ cm ⁻³ , and n ⁺ -GaAs Is doped with 3 × 10 ¹⁹ cm ⁻³ of silicon (Si).

The tunnel junction layer 207 includes disordered regions 207A and 207C and an ordered region 207B. Each of the regions 207A and 207C is made of [p ⁺ -GaAs / n ⁺ -GaAs] implanted with Ga ions, and the region 207B is made of [p ⁺ -GaAs / n ⁺ -GaAs] not implanted with Ga ions. Become.

  In each of the regions 207A and 207C, the impurity (C, Si) doped at a high concentration diffuses mutually in the region of the tunnel junction, and the carrier concentration decreases, so that the tunnel junction is broken. Therefore, in the regions 207A and 207C, no current flows due to the pn reverse bias junction, and a current blocking structure is formed.

  As a result, the current is confined in the region of the tunnel junction of the region 207B that is not disordered and injected into the active layer 204. The region 207B has a length of 4 μm in the in-plane direction DR2.

The reflective layer 208 is formed from [n-GaAs / n-Al _0.9 Ga _0.1 As] of 26 periods when a pair of n-GaAs / n-Al _0.9 Ga _0.1 As is taken as one period. And formed on the tunnel junction layer 207. Each of n-GaAs and n-Al _0.9 Ga _0.1 As has a film thickness of λ ₂ / 4n (n is the refractive index of the semiconductor layer).

  The p-side electrode 209 is formed on a part of the reflective layer 208 excluding the emission port 208A. The n-side electrode 210 is formed on the back surface of the substrate 201.

  Each of the reflective layers 202 and 208 constitutes a semiconductor distributed Bragg reflector that reflects the oscillation light oscillated in the active layer 204 by Bragg multiple reflection and confines it in the active layer 204. The interval between the reflective layer 202 and the reflective layer 208 is an optical length corresponding to one wavelength of the oscillation wavelength (= 980 nm). The resonator spacer layers 203 and 205 sandwiched between the reflective layers 202 and 208, the active layer The layer 204, the superlattice structure film 206, and the tunnel junction layer 207 constitute a resonator.

  The superlattice structure film 206 is formed in a region other than the reflective layers 202 and 208 and the active layer 204 on the emission port 208A side of the active layer 204. In the superlattice structure film 206, each of the disordered regions 206A and 206C has a refractive index lower than the refractive index of the ordered region 206B. The oscillated oscillation light is confined in the region 206B by the regions 206A and 206C, and the oscillation light is allowed to pass through the region 206B in the direction of the emission port 208A. Thereby, the transverse mode of the surface emitting laser element 100A is stabilized. That is, in the surface emitting laser element 100A, the higher-order oscillation mode is suppressed, and oscillation light consisting of only a single fundamental oscillation mode is emitted.

The superlattice structure film 206 has a periodic structure of [p-GaAs / p-Al _0.4 Ga _0.6 As], and the active layer 204 has a multiple quantum well structure of [GaInAs / GaAs]. The superlattice structure film 206 has a band gap larger than the band gap of the active layer 204. Therefore, the superlattice structure film 206 does not absorb the oscillation light oscillated in the active layer 204 and forms a waveguide structure with low loss.

  The tunnel junction layer 207 is formed in contact with the superlattice structure film 206. As a result, the regions 207A, 207B, and 207C are formed in contact with the regions 206A, 206B, and 206C of the superlattice structure film 206, respectively. The regions 207A and 207C of the tunnel junction layer 207 break the tunnel junction and form a current blocking structure by a pn reverse junction, so that the current injected from the p-side electrode 209 flows to the active layer 204 side. And the region through which the current passes is limited to the region 207B.

  6 and 7 are first and second process diagrams showing a method of manufacturing the surface-emitting laser element 100A shown in FIG. Referring to FIG. 6, when a series of operations is started, the reflective layer 202, the resonator spacer layer 203, the active layer 204, the resonator spacer layer 205, the superlattice structure film 206, and the tunnel junction are used using the MOCVD method. The layer 207 is sequentially stacked on the substrate 201 (see step (a) in FIG. 6).

In this case, n-GaAs and n-Al _0.9 Ga _0.1 As for the reflective layer 202 are replaced with trimethylaluminum (TMA), trimethylgallium (TMG), arsine (AsH ₃ ), and hydrogen selenide (H ₂ Se). Form as a raw material.

Further, n-GaAs of the resonator spacer layer 203 is formed using trimethyl gallium (TMG), arsine (AsH ₃ ), and silane (SiH ₄ ) as raw materials, and GaInAs / GaAs of the active layer 204 is formed using trimethyl gallium (TMG), trimethyl. indium (TMI) and arsine (AsH ₃₎ for the raw material.

Further, p-GaAs of the resonator spacer layer 205 is formed using trimethyl gallium (TMG), arsine (AsH ₃ ), and carbon tetrabromide (CBr ₄ ) as raw materials, and p-GaAs and p− of the superlattice structure film 206 are formed. Al _0.4 Ga _0.6 As is formed using trimethylaluminum (TMA), trimethylgallium (TMG), arsine (AsH ₃ ), and carbon tetrabromide (CBr ₄ ) as raw materials.

Further, p ⁺ -GaAs of the tunnel junction layer 207 is formed using trimethylgallium (TMG), arsine (AsH ₃ ), and carbon tetrabromide (CBr ₄ ) as raw materials, and n ⁺ -GaAs is formed of trimethylgallium (TMG), arsine. (AsH ₃ ) and silane (SiH ₄ ) are used as raw materials.

  Thereafter, a SiN film 220 is formed on the tunnel junction layer 207, and a patterned resist pattern 230 is formed on the formed SiN film 220 (see step (b) in FIG. 6). In this case, the resist pattern 230 has a circular shape with a diameter of 4 μm.

  When the resist pattern 230 is formed, the SiN film 220 is removed by etching using the formed resist pattern 230 as a mask, and the resist pattern 230 is further removed (see step (c) in FIG. 6). Thereby, the SiN film 221 is formed on the tunnel junction layer 207. Then, Ga ions are implanted using the SiN film 221 as a mask (see FIG. 6D).

  Next, referring to FIG. 7, when the ion implantation is completed in step (d) shown in FIG. 6 and the SiN film 221 is removed by etching, the disordered regions 206A and 206C and the ordered regions 206B Are formed in the superlattice structure film 206, and the disordered regions 207A and 207C and the ordered region 207B are formed in the tunnel junction layer 207 (see FIG. 7E).

Thereafter, the reflective layer 208 is formed on the tunnel junction layer 207 by MOCVD (see FIG. 7F). In this case, n-GaAs / n-Al _0.9 Ga _0.1 As for the reflective layer 208 is formed using trimethylaluminum (TMA), trimethylgallium (TMG), arsine (AsH ₃ ), and silane (SiH ₄ ) as raw materials. To do.

  Then, the p-side electrode 209 is formed on a part of the reflective layer 208 by vapor deposition and lift-off, and the n-side electrode 210 is formed on the back surface of the substrate 201 by vapor deposition (see (g) of FIG. 7). Thereby, the surface emitting laser element 100A is completed.

  When oscillating the surface emitting laser element 100A, lead wires are connected to the p-side electrode 209 and the n-side electrode 210, and current is injected from the p-side electrode 209. Then, in surface emitting laser element 100A, regions 207A and 207C of tunnel junction layer 207 restrict the current passing region injected from p-side electrode 209 to region 207C and inject current into active layer 204.

  When the current injected into the active layer 204 reaches the threshold current, oscillation light is generated in the active layer 204, and the generated oscillation light is reflected by the reflection layers 202 and 208. Further, the regions 206A and 206C of the superlattice structure film 206 confine the oscillation light in the region 206B. As a result, the oscillation light oscillates in a single mode and is radiated from the emission port 208A.

  As described above, in the surface emitting laser element 100A, the tunnel junction layer 207 limits the current injection region to the region 207B by the regions 207A and 207C and injects current into the active layer 204. The oscillation light oscillated in the active layer 204 is confined in the region 206B by the regions 206A and 206C. Since the disordered regions 206A and 206C; 207A and 207C are formed in regions other than the active layer 204 and the reflective layers 202 and 208, an increase in defect density in the active layer 204 is suppressed. Accordingly, the surface emitting laser element 100A can oscillate single mode oscillation light with a low threshold current.

  In addition, in the superlattice structure film 206 and the tunnel junction layer 207 of the surface emitting laser element 100A, a part of the regions 206A, 206C; 207A, 207C is simultaneously disordered in one step ((d) in FIG. 6). And (e) of FIG. 7), the manufacturing process of the surface emitting laser element 100A is facilitated.

  Furthermore, Ga ions that do not increase the carrier concentration are used to disorder the superlattice structure film 206 and some regions 206A, 206C; 207A, 207C of the tunnel junction layer 207. Therefore, by not increasing the carrier concentration in the regions 206A, 206C; 207A, 207C, the light absorption loss due to free carriers does not increase in the regions 206A, 206C; 207A, 207C. As a result, the slope efficiency of the surface emitting laser element 100A does not decrease, and a highly efficient surface emitting laser element can be manufactured.

  In the above, Ga ions are implanted into the superlattice structure film 206 and the tunnel junction layer 207 to form disordered regions 206A and 206C; 207A and 207C of the superlattice structure film 206 and the tunnel junction layer 207. However, in the present invention, the present invention is not limited to this. An electrically inactive element such as argon (Ar) and krypton (Kr) or aluminum (Al), indium (In), arsenic (As), and phosphorus The disordered regions 206A and 206C; 207A and 207C may be formed by ion implantation of a crystal constituent element such as (P) into the superlattice structure film 206 and the tunnel junction layer 207.

  In this case, since the ion-implanted element does not function as an acceptor and a donor, the carrier concentration in the disordered regions 206A and 206C; 207A and 207C is not increased. As a result, light absorption loss due to free carriers does not increase in the disordered regions 206A and 206C; 207A and 207C. Therefore, the slope efficiency of the surface emitting laser element 100A does not decrease, and a highly efficient surface emitting laser element can be manufactured.

  In the above description, it has been described that the interval between the reflective layer 202 and the reflective layer 208 is set to one wavelength of the oscillation wavelength (= 980 nm). However, the present invention is not limited to this, and the reflective layer 202 is not limited thereto. The distance between the reflective layer 208 and the reflective layer 208 may be set longer than one wavelength of the oscillation wavelength (= 980 nm).

  In the surface-emitting laser device 100A, in order for the active layer 204 to be positioned at the antinode of the optical standing wave and phase-matched, the resonator spacer layers 203 and 205, the active layer 204, the superlattice structure film 206, and the tunnel junction layer The length of the resonator composed of 207 (length in the direction DR1) needs to be set to ½ × natural number times the optical distance of the oscillation wavelength (= 980 nm). For this reason, in the surface emitting laser element 100A, the length of the resonator is normally set to one time the optical distance of the oscillation wavelength (= 980 nm).

  However, since the length of the resonator only needs to be set to a half of the optical distance of the oscillation wavelength (= 980 nm) × natural number times, the length of the resonator is the optical wavelength of the oscillation wavelength (= 980 nm). You may set the distance longer than 1 time of distance. This makes it possible to move the superlattice structure film 206 and the tunnel junction layer 207 away from the active layer 204 in the resonator, and when the superlattice structure and the tunnel junction are disordered by ion implantation, the active layer 204 is disordered. Therefore, the reactive current in the active layer 204 is suppressed, and the surface emitting laser element 100A can be operated with a low threshold current.

  Further, in the above description, the active layer 204 has been described as having a GaInAs / GaAs multiple quantum well structure. However, in the present invention, the present invention is not limited to this, and the active layer 204 includes N, V group elements other than N, and It may be configured using a mixed crystal semiconductor containing.

  The mixed crystal semiconductor containing N and a group V element other than N is made of the mixed crystal semiconductor described in the first embodiment. A mixed crystal semiconductor containing N and a group V element other than N has a band gap of a long wavelength band of 1.3 to 1.6 μm suitable for transmission through a quartz optical fiber, and is a barrier made of GaAs or the like. Since the barrier height when electrons in the conduction band are confined in the well layer between the layers can be increased, overflow of electrons from the active layer 204 is suppressed, and N and V group elements other than N are included. The surface emitting laser element 100A using a mixed crystal semiconductor for the active layer 204 has good temperature characteristics.

  Further, since a mixed crystal semiconductor containing N and a group V element other than N can be epitaxially grown on the GaAs substrate, a surface using a mixed crystal semiconductor containing a group V element other than N and N as the active layer 204 is used. In the light-emitting laser element, a GaAs / AlGaAs-based (especially GaAs / AlAs) reflective layer having high reflectivity and excellent thermal conductivity can be used as a multilayer film reflecting mirror. Therefore, a high-performance long-wavelength surface emitting laser element can be manufactured.

  The superlattice structure film 206 constitutes an “optical layer”, the ordered region 206B constitutes a “light passage layer”, and the disordered regions 206A and 206C constitute “light confinement layers”. Configure.

  The ordered region 206B constitutes a “first superlattice structure film”, and the disordered regions 206A and 206C constitute a “second superlattice structure film”.

  Further, the tunnel junction layer 207 constitutes a “current injection layer”, the regions 207A and 207C constitute a “current confinement layer”, and the region 207C constitutes a “current passage layer”.

  Further, the resonator spacer layer 203 constitutes a “first resonator spacer layer”, and the resonator spacer layer 205 constitutes a “second resonator spacer layer”.

  Further, the reflective layer 202 constitutes a “first reflective layer”, and the reflective layer 208 constitutes a “second reflective layer”.

[Embodiment 3]
FIG. 8 is a schematic cross-sectional view of the surface emitting laser element according to the third embodiment. Referring to FIG. 8, surface emitting laser element 100B according to Embodiment 3 includes resonator spacer layers 203 and 205, active layer 204, superlattice structure film 206, and tunnel junction layer of surface emitting laser element 100A shown in FIG. 207 is replaced with the resonator spacer layers 301, 303, 305, and 307, the superlattice structure film 302, the active layer 304, and the tunnel junction layer 306, and the others are the same as those of the surface emitting laser element 100A. The surface emitting laser element 100B is a surface emitting laser element in which the wavelength λ _{3 of the} oscillation light is 1300 nm.

The resonator spacer layer 301 is made of n-GaAs and is formed on the reflective layer 202. Superlattice structure layer 302, when a one cycle pairs _{n-GaAs / n-Al 0.4} Ga 0.6 As, four periods _{[n-GaAs / n-Al} 0.4 Ga 0.6 As And is formed on the resonator spacer layer 301. Each of the n-GaAs and _n-Al 0.4 _{Ga 0.6} As has thickness of 4 nm.

The superlattice structure film 302 includes disordered regions 302A and 302C and an ordered region 302B. Region 302A, each 302C consists superlattice structure membrane was implanted Ga ions _{[n-GaAs / n-Al} 0.4 Ga 0.6 As], region 302B is not implanted Ga ions [ consisting superlattice structure layer of _{n-GaAs / n-Al 0.4} Ga 0.6 As]. Each of the regions 302A and 302C has a refractive index lower than that of the region 302B. The region 302B has a length of 3 μm in the in-plane direction DR2.

  The resonator spacer layer 303 is made of n-GaAs and is formed on the superlattice structure film 302. The active layer 304 has a multi-quantum well structure composed of [GaInNAs / GaAs] having three periods when a pair of GaInNAs / GaAs is defined as one period, and is formed on the resonator spacer layer 303. GaInNAs has a thickness of 8 nm, and GaAs has a thickness of 15 nm.

The resonator spacer layer 305 is made of p-GaAs and is formed on the active layer 304. The tunnel junction layer 306 is made of p ⁺ -GaAs / n ⁺ -GaAs and is formed on the resonator spacer layer 305. In this case, p ⁺ -GaAs is formed on the resonator spacer layer 305 side. Each film thickness of p ⁺ -GaAs and n ⁺ -GaAs is 10 nm, p ⁺ -GaAs is doped with C of 1 × 10 ²⁰ cm ⁻³ , and n ⁺ -GaAs is 3 × 10 ¹⁹ cm ⁻³ of Si is doped.

The tunnel junction layer 306 includes disordered regions 306A and 306C and ordered regions 306B. Each of the regions 306A and 306C is made of [p ⁺ -GaAs / n ⁺ -GaAs] implanted with Ga ions, and the region 306B is made of [p ⁺ -GaAs / n ⁺ -GaAs] not implanted with Ga ions. Become.

  In each of the regions 306A and 306C, the impurity (C, Si) doped at a high concentration mutually diffuses in the region of the tunnel junction, and the carrier concentration decreases, so that the tunnel junction is broken. Therefore, in the regions 306A and 306C, no current flows due to the pn reverse bias junction, and a current blocking structure is formed.

  As a result, current is confined in the region of the tunnel junction in the region 306B that is not disordered and injected into the active layer 304. The region 306B has a length of 5 μm in the in-plane direction DR2. Therefore, in the surface emitting laser element 100B, the region 306B of the tunnel junction layer 306 is wider than the region 302B of the superlattice structure film 302.

  The resonator spacer layer 307 is made of n-GaAs and is formed on the tunnel junction layer 306.

In the surface emitting laser element 100B, each of the n-GaAs and n-Al _0.9 Ga _0.1 As constituting each of the reflective layers 202 and 208 is λ ₃ / 4n (n is the refraction in the semiconductor layer). Rate) film thickness.

  In the surface emitting laser element 100B, the distance between the reflective layer 202 and the reflective layer 208 is an optical length corresponding to three wavelengths of the oscillation wavelength (= 1300 nm), and the resonator spacer is sandwiched between the reflective layers 202 and 208. The layers 301, 303, 305, and 307, the superlattice structure film 302, the active layer 304, and the tunnel junction layer 306 constitute a resonator.

  In the superlattice structure film 302, each of the disordered regions 302A and 302C has a refractive index lower than that of the ordered region 302B, so that the superlattice structure film 302 oscillates in the active layer 304. The oscillation light is confined in the region 302B by the regions 302A and 302C, and the oscillation light is passed through the region 302B in the direction of the emission port 208A. Thereby, the transverse mode of the surface emitting laser element 100B is stabilized. That is, in the surface emitting laser element 100B, the higher-order oscillation mode is suppressed, and oscillation light consisting of only a single fundamental oscillation mode is emitted.

The superlattice structure film 302 has a periodic structure of [n-GaAs / n-Al _0.4 Ga _0.6 As], and the active layer 304 has a multiple quantum well structure of [GaInNAs / GaAs]. The superlattice structure film 302 has a band gap larger than the band gap of the active layer 304. Therefore, the superlattice structure film 302 does not absorb the oscillation light oscillated in the active layer 304, and forms a waveguide structure with low loss.

  The regions 306A and 306C of the tunnel junction layer 306 break the tunnel junction and form a current blocking structure. Therefore, the current injected from the p-side electrode 209 is prevented from flowing to the active layer 304 side, and the current flows. The passing area is limited to the area 306B.

  In the surface emitting laser element 100B, the superlattice structure film 302 is formed closer to the substrate 201 than the active layer 304 in a region other than the reflective layers 202 and 208 and the active layer 304, and the tunnel junction layer 306 is the active layer 304. Rather than the exit 208A side. That is, the superlattice structure film 302 and the tunnel junction layer 306 are formed on the opposite sides of the active layer 304 in regions other than the reflective layers 202 and 208 and the active layer 304.

  When the resonator spacer layers 301 and 303 are considered as one resonator spacer layer and the resonator spacer layers 305 and 307 are considered as one resonator spacer layer, the superlattice structure film 302 and the tunnel junction layer 306 are: It will be formed in the resonator spacer layer.

  9, 10, and 11 are first to third process diagrams illustrating a method for manufacturing the surface-emitting laser element 100 </ b> B illustrated in FIG. 8, respectively. Referring to FIG. 9, when a series of operations starts, MOCVD is used to sequentially stack reflective layer 202, resonator spacer layer 301, and superlattice structure film 302 on substrate 201 (step of FIG. 9). (See (a)).

In this case, n-GaAs and n-Al _0.9 Ga _0.1 As for the reflective layer 202 are replaced with trimethylaluminum (TMA), trimethylgallium (TMG), arsine (AsH ₃ ), and hydrogen selenide (H ₂ Se). Form as a raw material.

Further, n-GaAs of the resonator spacer layer 301 is formed using trimethyl gallium (TMG), arsine (AsH ₃ ), and silane (SiH ₄ ) as raw materials, and the n-GaAs / n-Al _{0. 4} Ga _0.6 As is formed using trimethylaluminum (TMA), trimethylgallium (TMG), arsine (AsH ₃ ), and silane (SiH ₄ ) as raw materials.

  Thereafter, a SiN film 320 is formed on the superlattice structure film 302, and a patterned resist pattern 330 is formed on the formed SiN film 320 (see step (b) in FIG. 9). In this case, the resist pattern 330 has a circular shape with a diameter of 3 μm.

  When the resist pattern 330 is formed, the SiN film 320 is removed by etching using the formed resist pattern 330 as a mask, and the resist pattern 330 is further removed. Thereby, the SiN film 321 is formed on the superlattice structure film 302. Then, Ga ions are ion-implanted using the SiN film 321 as a mask (see FIG. 9C), and subsequently, heat treatment is performed at 700 ° C. to recover the crystallinity of the region into which Ga ions are implanted. Then, when the SiN film 321 is removed by etching, disordered regions 302A and 302C and ordered regions 302B are formed in the superlattice structure film 302 (see FIG. 9D).

  Next, referring to FIG. 10, when step (d) shown in FIG. 9 is completed, the resonator spacer layer 303, the active layer 304, the resonator spacer layer 305, and the tunnel junction layer 306 are formed into a superlattice structure by MOCVD. The layers are sequentially stacked on the film 302 (see FIG. 10E).

In this case, n-GaAs of the resonator spacer layer 303 is formed using trimethyl gallium (TMG), arsine (AsH ₃ ), and silane (SiH ₄ ) as raw materials, and GaInNAs of the active layer 304 is formed using trimethyl gallium (TMG), trimethyl indium. (TMI), dimethylhydrazine (DMH _y ), and arsine (AsH ₃ ) are formed as raw materials, and GaAs of the active layer 304 is formed using trimethyl gallium (TMG) and arsine (AsH ₃ ) as raw materials.

Further, p-GaAs of the resonator spacer layer 305 is formed using trimethyl gallium (TMG), arsine (AsH ₃ ), and carbon tetrabromide (CBr ₄ ) as raw materials, and p ⁺ -GaAs of the tunnel junction layer 306 is formed of trimethyl gallium. (TMG), arsine (AsH ₃ ) and carbon tetrabromide (CBr ₄ ) are used as raw materials, and n ⁺ -GaAs of the tunnel junction layer 306 is changed to trimethylgallium (TMG), arsine (AsH ₃ ) and silane (SiH ₄ ). ) As a raw material.

  Thereafter, a SiN film 340 is formed on the tunnel junction layer 306, and a patterned resist pattern 350 is formed on the formed SiN film 340 (see step (f) in FIG. 10). In this case, the resist pattern 350 has a circular shape with a diameter of 5 μm.

  When the resist pattern 350 is formed, the SiN film 340 is removed by etching using the formed resist pattern 350 as a mask, and the resist pattern 350 is further removed. Thereby, the SiN film 341 is formed on the tunnel junction layer 306. Then, Ga ions are ion-implanted using the SiN film 341 as a mask (see (g) of FIG. 10), followed by annealing. Thereafter, when the SiN film 341 is removed by etching, disordered regions 306A and 306C and ordered regions 306B are formed in the tunnel junction layer 306 (see FIG. 10H).

  Referring to FIG. 11, when step (h) shown in FIG. 10 is completed, resonator spacer layer 307 and reflective layer 208 are sequentially stacked on tunnel junction layer 306 by MOCVD (see FIG. 11 (i)). ).

In this case, n-GaAs of the resonator spacer layer 307 is formed using trimethyl gallium (TMG), arsine (AsH ₃ ), and silane (SiH ₄ ) as raw materials, and n-GaAs and n-Al _{0.9 of the} reflective layer 208 are formed. Ga _0.1 As is formed using trimethylaluminum (TMA), trimethylgallium (TMG), arsine (AsH ₃ ), and silane (SiH ₄ ) as raw materials.

  Then, the p-side electrode 209 is formed on a part of the reflective layer 208 by vapor deposition and lift-off, and the n-side electrode 210 is formed on the back surface of the substrate 201 by vapor deposition (see (j) of FIG. 11). Thereby, the surface emitting laser element 100B is completed.

  When the surface emitting laser element 100B is oscillated, lead wires are connected to the p-side electrode 209 and the n-side electrode 210, and current is injected from the p-side electrode 209. Then, in the surface emitting laser element 100B, the regions 306A and 306C of the tunnel junction layer 306 limit the current passing region injected from the p-side electrode 209 to the region 306C and inject current into the active layer 304.

  When the current injected into the active layer 304 reaches the threshold current, oscillation light is generated in the active layer 304, and the generated oscillation light is reflected by the reflection layers 202 and 208. In addition, the regions 302A and 302C of the superlattice structure film 302 confine the oscillation light in the region 302B. As a result, the oscillation light oscillates in a single mode and is radiated from the emission port 208A.

  Thus, in the surface emitting laser element 100B, the tunnel junction layer 306 restricts the current injection region to the region 306B by the regions 306A and 306C and injects the current into the active layer 304. The oscillation light oscillated in the active layer 304 is confined in the region 302B by the regions 302A and 302C. Since the disordered regions 302A and 302C; 306A and 306C are formed in regions other than the active layer 304 and the reflective layers 202 and 208, an increase in defect density in the active layer 304 is suppressed. Therefore, the surface emitting laser element 100B can oscillate single mode oscillation light with a low threshold current.

  Further, since the region 306B of the tunnel junction layer 306 of the surface emitting laser element 100B is formed to be wider than the region 302B of the superlattice structure film 302, the light emitting region of the surface emitting laser element 100B is widened. As a result, the emission intensity of the surface emitting laser element 100B can be improved.

  Further, the surface emitting laser element 100B is characterized in that the interval between the reflective layer 202 and the reflective layer 208 is set to three wavelengths longer than one wavelength of the oscillation wavelength (= 1300 nm).

  In the surface-emitting laser element 100B, in order for the active layer 304 to be positioned at the antinode of the optical standing wave and phase-matched, the resonator spacer layers 301, 303, 305, and 307, the superlattice structure film 302, and the active layer 304 In addition, the length of the resonator formed of the tunnel junction layer 306 (length in the direction DR1) needs to be set to ½ × natural number times the optical distance of the oscillation wavelength (= 1300 nm). For this reason, in the surface emitting laser element 100B, the length of the resonator is normally set to one time the optical distance of the oscillation wavelength (= 1300 nm).

  However, since the length of the resonator only needs to be set to ½ × natural number times the optical distance of the oscillation wavelength (= 1300 nm), the length of the resonator is the optical wavelength of the oscillation wavelength (= 1300 nm). You may set the distance longer than 1 time of distance. As a result, the superlattice structure film 302 and the tunnel junction layer 306 can be moved away from the active layer 304 in the resonator, and when the superlattice structure and the tunnel junction are disordered by ion implantation, the active layer 304 is disordered. Therefore, the reactive current in the active layer 304 is suppressed, and the surface emitting laser element 100B can be operated with a low threshold current.

  Furthermore, in order to disorder the superlattice structure film 302 and some regions 302A and 302C; 306A and 306C of the tunnel junction layer 306, Ga ions that do not increase the carrier concentration are used. Therefore, by not increasing the carrier concentration in the regions 302A, 302C; 306A, 306C, the light absorption loss due to free carriers does not increase in the regions 302A, 302C; 306A, 306C. As a result, the slope efficiency of the surface emitting laser element 100B does not decrease, and a highly efficient surface emitting laser element can be manufactured.

  In the above, Ga ions are ion-implanted into the superlattice structure film 302 and the tunnel junction layer 306 to form disordered regions 302A and 302C; 306A and 306C of the superlattice structure film 302 and the tunnel junction layer 306. However, in the present invention, the present invention is not limited to this. An electrically inactive element such as argon (Ar) and krypton (Kr) or aluminum (Al), indium (In), arsenic (As), and phosphorus The disordered regions 302A and 302C; 306A and 306C may be formed by ion implantation of a crystal constituent element such as (P) into the superlattice structure film 302 and the tunnel junction layer 306.

  In this case, since the ion-implanted element does not function as an acceptor and a donor, the carrier concentration of the disordered regions 302A and 302C; 306A and 306C is not increased. As a result, light absorption loss due to free carriers does not increase in the disordered regions 302A and 302C; 306A and 306C. Therefore, the slope efficiency of the surface emitting laser element 100B does not decrease, and a highly efficient surface emitting laser element can be manufactured.

  In the above description, the superlattice structure film 302 is formed closer to the substrate 201 than the active layer 304 in a region other than the reflective layers 202 and 208 and the active layer 304, and the tunnel junction layer 306 is more than the active layer 304. In the present invention, the superlattice structure film 302 is not limited to this, but the superlattice structure film 302 is emitted from the active layer 304 in a region other than the reflective layers 202 and 208 and the active layer 304. The tunnel junction layer 306 may be formed closer to the substrate 201 than the active layer 304.

  In this case, the diameter of the region 302B of the superlattice structure film 302 is set to a value larger than the diameter of the region 306B of the tunnel junction layer 306.

  Further, in the above description, the active layer 304 has been described as having a GaInNAs / GaAs multiple quantum well structure. However, the present invention is not limited to this, and the active layer 304 is not limited to GaInNAs but other than N and N. A mixed crystal semiconductor containing a group element may be used.

  The mixed crystal semiconductor containing N and a group V element other than N is made of the mixed crystal semiconductor described in the first embodiment. A mixed crystal semiconductor containing N and a group V element other than N has a band gap of a long wavelength band of 1.3 to 1.6 μm suitable for transmission through a quartz optical fiber, and is a barrier made of GaAs or the like. Since the barrier height when confining electrons in the conduction band between the layers to the well layer can be increased to 300 meV or more, overflow of electrons from the active layer 304 is suppressed, and V group elements other than N and N The surface emitting laser element 100B using the mixed crystal semiconductor containing as the active layer 304 has good temperature characteristics.

  Further, since a mixed crystal semiconductor containing N and a group V element other than N can be epitaxially grown on a GaAs substrate, a surface using a mixed crystal semiconductor containing a group V element other than N and N for the active layer 304 is used. In the light-emitting laser element, a GaAs / AlGaAs-based (especially GaAs / AlAs) reflective layer having high reflectivity and excellent thermal conductivity can be used as a multilayer film reflecting mirror. Therefore, a high-performance long-wavelength surface emitting laser element can be manufactured.

  The superlattice structure film 302 constitutes an “optical layer”, the ordered region 302B constitutes a “light passage layer”, and the disordered regions 302A and 302C constitute “light confinement layers”. Configure.

  Further, the ordered region 302B constitutes a “first superlattice structure film”, and the disordered regions 302A and 302C constitute a “second superlattice structure film”.

  Further, the tunnel junction layer 306 constitutes a “current injection layer”, the regions 306A and 306C constitute a “current confinement layer”, and the region 306C constitutes a “current passing layer”.

  Furthermore, the resonator spacer layers 301 and 303 constitute a “first resonator spacer layer”, and the resonator spacer layers 305 and 307 constitute a “second resonator spacer layer”.

  Others are the same as in the second embodiment.

  In the first to third embodiments described above, the terms “disordered region” and “ordered region” are used. In the present invention, the term “disordered region” is used. Is a region where the periodicity of the superlattice is broken due to the inclusion of an electrically inactive element or crystal constituent element in the superlattice structure film, and the electrically inactive element in the tunnel junction layer Or the area | region where the tunnel junction is destroyed by entering a crystal | crystallization constituent element.

  In the present invention, the “ordered region” means that the superlattice structure film does not contain an electrically inactive element or a crystal constituent element, and the periodicity of the superlattice is maintained. In the tunnel junction layer, the region where no electrically inactive element or crystal constituent element is contained and current flows through the tunnel junction.

[Application example]
FIG. 12 is a schematic diagram of an optical transmission system using the surface emitting laser element according to the present invention. Referring to FIG. 12, an optical transmission system 400 using a surface emitting laser element according to the present invention includes an optical transmission module 410, an optical reception module 420, and an optical fiber cable 430.

  The optical transmission module 410 includes a drive circuit 411 and a surface emitting laser element 412. The surface emitting laser element 412 includes the surface emitting laser element 100B shown in FIG. The optical receiving module 420 includes a light receiving element 421 and a receiving circuit 422. The drive circuit 411 modulates the current injected into the active layer 304 of the surface emitting laser element 412 and modulates the intensity of the laser beam output from the surface emitting laser element 412.

  The surface emitting laser element 412 emits oscillation light having modulated laser light intensity to the optical fiber cable 430 in accordance with the driving from the driving circuit 411. The optical fiber cable 430 propagates the oscillation light emitted from the surface emitting laser element 412 to the optical reception module 420 as an optical signal.

  The light receiving element 421 of the optical receiving module 420 receives the optical signal propagated by the optical fiber cable 430 and converts the received optical signal into an electrical signal. Then, the light receiving element 421 outputs the converted electric signal to the receiving circuit 422. The receiving circuit 422 performs signal amplification, waveform shaping, and the like on the electrical signal received from the light receiving element 421 and outputs the signal to the outside.

  In this way, in the optical transmission system 400, the optical signal is propagated from the optical transmission module 410 to the optical reception module 420 via the optical fiber cable 430, converted into an electrical signal in the optical reception module 420, and the optical reception module 420. Is output to the outside.

  The optical transmission module 410 includes a surface emitting laser element 412 (= surface emitting laser element 100B) as a light source. As described above, the surface emitting laser element 100B operates with a low threshold current with the reactive current in the active layer 304 suppressed, and operates stably in a single transverse mode. Therefore, an optical transmission module having low power consumption and high transmission reliability can be formed. Further, the optical transmission system 400 can also realize low power consumption and high transmission reliability.

  In the optical transmission system 400, the surface emitting laser element 412 may be configured by either the surface emitting laser element 100 or 100A.

  12 shows a configuration example of unidirectional communication of a single channel, the optical transmission system 400 can also adopt configurations such as bidirectional communication, a parallel transmission scheme, and a wavelength division multiplex transmission scheme. .

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include meanings equivalent to the scope of claims for patent and all modifications within the scope.

  The present invention is applied to a surface emitting laser element that can operate in a single mode with a low threshold current. In addition, the present invention is applied to an optical transmission module including a surface emitting laser element that can operate in a single mode with a low threshold current. Furthermore, the present invention is applied to an optical transmission system including a surface emitting laser element that can operate in a single mode with a low threshold current.

It is a schematic sectional drawing of the surface emitting laser element by Embodiment 1 of this invention. FIG. 3 is a first process diagram showing a method for manufacturing the surface emitting laser element shown in FIG. 1. FIG. 6 is a second process diagram illustrating a method for manufacturing the surface emitting laser element illustrated in FIG. 1. FIG. 6 is a third process diagram illustrating a method for manufacturing the surface emitting laser element illustrated in FIG. 1. 6 is a schematic cross-sectional view of a surface emitting laser element according to a second embodiment. FIG. FIG. 6 is a first process chart showing a method for manufacturing the surface emitting laser element shown in FIG. 5. FIG. 6 is a second process diagram showing a method for manufacturing the surface emitting laser element shown in FIG. 5. 6 is a schematic cross-sectional view of a surface emitting laser element according to Embodiment 3. FIG. FIG. 9 is a first process chart showing a method for manufacturing the surface emitting laser element shown in FIG. 8. FIG. 9 is a second process diagram illustrating a method of manufacturing the surface emitting laser element illustrated in FIG. 8. FIG. 10 is a third process diagram illustrating a method of manufacturing the surface emitting laser element illustrated in FIG. 8. It is the schematic of the optical transmission system using the surface emitting laser element by this invention.

Explanation of symbols

  100, 100A, 100B, 412 Surface emitting laser element, 101, 201 substrate, 102, 107, 202, 208 reflective layer, 103, 105, 203, 205, 301, 303, 305, 307 Cavity spacer layer, 104, 204 , 304 active layer, 106, 206, 302 superlattice structure film, 106A, 106B, 106C, 108C, 206A, 206B, 206C, 207A, 207B, 207C, 302A, 302B, 302C, 306A, 306B, 306C region, 107A, 208A Outlet, 108A, 108B High resistance layer, 109,209 p-side electrode, 110, 210 n-side electrode, 120, 121, 150, 151, 220, 221, 320, 321, 340, 341 SiN film, 130, 160 , 230, 330, 350 Resist pattern, 140 ZnO film, 207,306 tunnel junction layer, 400 optical transmission system, 410 optical transmission module, 411 drive circuit, 420 optical reception module, 421 light receiving element, 422 reception circuit, 430 optical fiber cable.

Claims (21)

An active layer,
A resonator spacer layer sandwiching the active layer;
A reflective layer that sandwiches the active layer and the resonator spacer layer and reflects oscillation light oscillated in the active layer;
A current injection layer for injecting current into the active layer by limiting a region through which current passes;
Provided in a region other than the active layer and the reflective layer, confining the oscillation light in a current passing region through which the current injected into the active layer passes in an in-plane direction substantially perpendicular to the emission direction of the oscillation light, An optical layer that allows the confined oscillation light to pass through to an emission port;
The optical layer is a surface emitting laser element that confines the oscillation light in the current passing region using a disordered superlattice structure film. The optical layer is
An ordered first superlattice structure film provided in the current passing region;
2. The surface-emitting laser device according to claim 1, further comprising a disordered second superlattice structure film provided outside the first superlattice structure film in the in-plane direction.   3. The surface emitting laser element according to claim 2, wherein each of the first and second superlattice structure films has a band gap larger than a band gap of the active layer.   The surface emitting laser element according to claim 2, wherein the optical layer is provided closer to the emission port than the active layer. The resonator spacer layer is
A first resonator spacer layer provided on the opposite side of the emission port with respect to the active layer;
A second resonator spacer layer provided on the exit side of the active layer,
The reflective layer is
A first reflective layer provided on the side opposite to the exit port with respect to the active layer;
A second reflective layer provided on the exit side of the active layer,
The surface emitting laser element according to claim 4, wherein the optical layer is provided between the second resonator spacer layer and the second reflective layer.   The surface emitting laser element according to claim 4, wherein the current injection layer is provided closer to the emission port than the active layer.   The surface emitting laser element according to claim 6, wherein the current injection layer is provided in the second reflective layer. The current injection layer is
A current passing layer having the same resistance as the second reflective layer;
The surface emitting laser element according to claim 7, comprising a current confinement layer provided outside the current passage layer in the in-plane direction and having a larger resistance than the current passage layer.   The surface emitting laser element according to claim 6, wherein the current injection layer is provided between the optical layer and the second reflective layer.   The surface emitting laser element according to claim 9, wherein the current injection layer is provided in contact with the optical layer. The current injection layer is
A current passing layer for passing the current to the active layer by a tunnel junction;
11. The current confinement layer according to claim 9, further comprising a current confinement layer provided outside the current passage layer in the in-plane direction and restricting the passage of the current to the active layer by a pn reverse junction. Surface emitting laser element.   The surface emitting laser element according to claim 2, wherein the current injection layer and the optical layer are provided on opposite sides of the active layer.   The surface emitting laser element according to claim 12, wherein the current injection layer and the optical layer are provided in the resonator spacer layer. The resonator spacer layer is
A first resonator spacer layer provided on the opposite side of the emission port with respect to the active layer;
A second resonator spacer layer provided on the exit side of the active layer,
The current injection layer is provided in the first resonator spacer layer;
The surface emitting laser element according to claim 13, wherein the optical layer is provided in the second resonator spacer layer. The current injection layer is
A current passing layer for passing the current to the active layer by a tunnel junction;
The surface emitting laser element according to claim 14, further comprising: a current confinement layer provided outside the current passage layer in the in-plane direction and restricting the passage of the current to the active layer by a pn reverse junction. .   The surface emitting laser element according to claim 15, wherein an area of the current passage layer is larger than an area of the first superlattice structure film.   The surface emitting laser element according to any one of claims 3 to 16, wherein the second superlattice structure film includes an electrically inactive element or a crystal constituent element.   18. The surface emitting laser element according to claim 1, wherein the sum of the thickness of the active layer and the thickness of the resonator spacer layer is longer than one wavelength of the oscillation light. .   19. The surface emitting laser element according to claim 1, wherein the active layer includes both a nitrogen element and a group V element other than the nitrogen element.   An optical transmission module comprising the surface emitting laser element according to any one of claims 1 to 19.   An optical transmission system comprising the optical transmission module according to claim 20.

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