JP5708956B2 - Surface emitting laser array, optical scanning device and image forming apparatus provided with the same - Google Patents

Description

  The present invention relates to a surface emitting laser array, an optical scanning device including the same, and an image forming apparatus.

  During the operation of the surface emitting laser array in which the surface emitting laser elements are densely integrated, the output of the surface emitting laser element decreases due to the temperature rise caused by the heat generated from the surrounding surface emitting laser elements. There was a problem that the life of the surface emitting laser array was shortened. For this reason, it is necessary to improve the heat dissipation characteristics. For example, a material having high thermal conductivity is used for the main Bragg reflector on the heat dissipation side. Of the materials that can be used for the semiconductor Bragg reflector of the surface emitting laser element on the GaAs substrate, AlAs has the highest thermal conductivity and is preferable.

  However, in some cases, a mesa shape or the like is etched in order to be electrically or spatially separated from the surroundings. In this case, although it is not necessary to perform etching until reaching the semiconductor Bragg reflector (lower semiconductor Bragg reflector) provided on the substrate side in terms of function, the bottom surface of the lower semiconductor Bragg is etched due to the problem of etching controllability. There are cases where the design is made assuming that the reflector is reached.

  For example, in an oxide confinement type surface emitting laser element, it is necessary to etch deeper than a selective oxidation layer in order to perform selective oxidation. For the purpose of suppressing the spread of current, the selective oxidation layer is located near the active layer of the p-side semiconductor Bragg reflector (semiconductor Bragg reflector provided above the active layer), that is, 1 to 1 from the active layer. Generally, it is provided at the position of the fifth node (the node in the electric field intensity distribution of the laser beam).

  However, due to the problem of controllability of the etching depth, it is difficult to control the etching bottom so that it is deeper than the selective oxidation layer and does not reach the lower semiconductor Bragg reflector. In particular, in order to control the etching depth throughout the wafer surface, in addition to controlling the etching time, the uniformity of etching within the wafer surface and further the thickness distribution of the crystal growth layer is made uniform. Therefore, it is extremely difficult in production to perform mesa etching so as not to enter the lower semiconductor Bragg reflector beyond the selective oxidation layer.

  For this reason, there exists a proposal (patent document 1) which makes a lower semiconductor Bragg reflector two steps. In this proposal, AlAs, which has a much higher thermal conductivity than AlGaAs, is used for most of the low refractive index layers on the substrate side of the lower semiconductor Bragg reflector. Conventional AlGaAs is used for the low refractive index layer on the active layer side of the lower semiconductor Bragg reflector.

  However, in the case of a surface emitting laser array, it has been found that it is more difficult to perform uniform mesa etching in the wafer surface for another reason. When the element gap of the surface emitting laser element is narrowed in order to arrange the array with high density, there is a difference Δd between the etching depth of the element gap and the etching depth of the flat portion around the surface emitting laser array. Furthermore, skirting occurs in the etched shape. In order to strictly control the oxidized constriction dimension, it is preferable that the selective oxidation layer does not cover the skirt portion. For this reason, if etching is performed so that the selectively oxidized layer does not cover the soaking portion, the etching bottom surface in the flat portion around the surface emitting laser array enters the lower semiconductor Bragg reflector. Since the low refractive index layer of the lower semiconductor Bragg reflector is usually thicker than the selective oxidation layer, the oxidation rate is faster than the selective oxidation layer with the same composition. When the oxidation rate of the low refractive index layer of the lower semiconductor Bragg reflector is faster than that of the selective oxidation layer, there arises a problem such that the entire low refractive index layer is oxidized and current injection cannot be performed. For this reason, AlAs could not be used for at least the low refractive index layer in the region close to the active layer of the lower semiconductor Bragg reflector. Therefore, conventionally, in order to slow down the oxidation rate of the semiconductor Bragg reflector, GaGaAs-added AlGaAs (for example, Al0.9Ga0.1As) had to be used (Non-Patent Documents 1 and 2).

  It has also been proposed to stop etching of the upper semiconductor Bragg reflector in the GaInP cladding layer (resonator region) (Patent Document 2).

  FIG. 29 is a plan view of a conventional surface emitting laser array. Referring to FIG. 29, a double dummy element is formed around the element portion where the surface emitting laser element is arranged. In Patent Document 3, it is pointed out that the post (mesa) in the peripheral part of the array and the post in the central part have different environments and the post shapes are different. Patent Document 3 proposes that a surface-emitting laser array having uniform characteristics can be provided by providing double dummy elements at the periphery of the array.

  In the conventional oxide confinement type surface emitting laser array, at least the etching bottom surface in the flat portion around the surface emitting laser array becomes a lower semiconductor Bragg reflector, so a material having high thermal conductivity such as an AlAs layer is Since it is easily oxidized when it appears on the surface by etching, it could not be used for the lower semiconductor Bragg reflector (at least in the region close to the active layer). For this reason, there is a problem that the active layer accumulates heat, the temperature of the active layer rises, the output of the surface emitting laser element decreases, and the element life is shortened. In particular, when operating with a surface emitting laser array, the adverse effect becomes prominent due to thermal interference, so it was not possible to operate with a high current, and it was necessary to use it with a low output. Moreover, the lifetime was short due to the temperature rise due to thermal interference.

  Further, based on the description in Patent Document 3, in order to prevent the etching bottom surface in the flat portion around the array from reaching the lower semiconductor Bragg reflector, a dummy element is formed on the entire wafer, thereby increasing the etching depth in the array portion. It is conceivable to reduce the difference Δd from the etching depth in the flat portion around the array. If the flat portion is not lost, the bottom surface of the etching reaches the lower semiconductor Bragg reflector and AlAs is oxidized, so it is necessary to form a dummy element on the entire wafer.

  However, if dummy elements are formed on the entire wafer, the area to be etched becomes small, and oxidation monitoring (plasma emission analysis, optical reflectance analysis, etc.) becomes difficult. In addition, if a dummy element is formed on the entire wafer, the probability of the disconnection of the wiring is increased because it is bumpy. Further, it is necessary to form a wire bonding pad for mounting. However, if there is a bump under the bonding pad, the mesa portion is broken at the time of wire bonding, resulting in a failure.

  Accordingly, the present invention has been made to solve such a problem, and an object thereof is to provide a surface emitting laser array in which heat is not easily trapped in an active layer without using a dummy element.

  Another object of the present invention is to provide an optical scanning device including a surface emitting laser array in which heat is not easily trapped in an active layer without using a dummy element.

  Furthermore, another object of the present invention is to provide an image forming apparatus provided with a surface emitting laser array in which heat is not easily trapped in an active layer without using a dummy element.

According to a first aspect of the present invention, there is provided an element arrangement portion in which a plurality of surface-emitting laser elements including a mesa structure formed by etching and provided on a substrate are arranged, and provided on the substrate. A surface-emitting laser array including a flat portion provided around the element arrangement portion in an in-plane direction of the substrate, wherein each of the plurality of surface-emitting laser elements includes a semiconductor Bragg reflector, A first reflection layer formed on the first reflection layer, a resonator formed on the first reflection layer, and a plurality of layers each made of an AlGaInPAs-based material containing at least In; and the semiconductor Bragg reflector And a second reflective layer including a selective oxidation layer having a current confinement structure formed on the resonator, wherein the first reflective layer has an oxidation rate equal to or greater than an oxidation rate of the selective oxidation layer. A low-refractive-index layer made of AlAs having a temperature of at least the resonator side, the second reflective layer comprising a layer made of an AlGaAs-based material, and the etching rate of the resonator is determined by the second reflective layer The etching bottom surface of the gap portion of the plurality of surface emitting laser elements and the etching bottom surface of the flat portion in the element placement portion are both slower than the etching rate of the layer made of the AlGaAs-based material. The resonator is located in a layer made of an AlGaInPAs-based material containing at least In, and the bottom surface of the gap portion of the plurality of surface emitting laser elements in the element arrangement portion is closer to the substrate than the bottom surface of the flat portion. This is a surface emitting laser array at a distant position.

  Preferably, the etching rate of the resonator is slower than the etching rate of the second reflective layer.

  Preferably, the second reflective layer includes a layer made of an AlGaInPAs-based material containing at least In on the active layer side.

  Preferably, the bottom surface of the mesa structure is located in the resonator or at the interface between the second reflective layer and the resonator.

  Preferably, the first reflective layer includes a low refractive index layer made of AlAs in all regions.

  Preferably, the current confinement structure is a selective oxidation type.

  Preferably, the difference between the etching depth in the gap portion and the etching depth in the flat portion is equal to or less than half of the oscillation wavelength of the surface emitting laser element as an effective length in the medium.

  Preferably, the distance between two surface emitting laser elements adjacent in the gap is such that the distance between the two mesa structures at the top surface position of the mesa structure and the distance between the two mesa structures at the bottom surface position of the mesa structure. Of the narrower one of which is 20 μm or less.

  According to a second aspect of the present invention, the surface emitting laser array of the present invention, a deflecting means for deflecting a plurality of beams emitted from the surface emitting laser array, and the beam from the deflecting means on the surface to be scanned. An optical scanning device including a scanning optical element that guides the light.

  From the third viewpoint, the present invention is an image forming apparatus including the optical scanning device of the present invention.

  From the fourth viewpoint, the present invention is an image forming apparatus including the surface emitting laser array of the present invention as a writing light source.

According to this invention, it can be thermally hardly confined to the active layer without using a dummy element.

It is a top view of the surface emitting laser array by Embodiment 1 of this invention. It is a schematic sectional drawing of the surface emitting laser element shown in FIG. It is sectional drawing which shows the vicinity of the active layer of the surface emitting laser element shown in FIG. FIG. 3 is a first process diagram illustrating a method for manufacturing the surface emitting laser array shown in FIG. 1. FIG. 4 is a second process diagram illustrating a method for manufacturing the surface emitting laser array illustrated in FIG. 1. FIG. 6 is a third process diagram illustrating a method for manufacturing the surface emitting laser array illustrated in FIG. 1. It is a figure for demonstrating in detail the etching in (b) of FIG. It is a 1st timing chart of the plasma emission at the time of etching when producing the surface emitting laser array shown in FIG. FIG. 4 is a second timing chart of plasma emission during etching when the surface emitting laser array shown in FIG. 1 is manufactured. It is a figure which shows the difference of the etching depth in the flat part at the time of stopping an etching in a resonator area | region, and the etching depth in the element gap part of a surface emitting laser element, and the etching depth in a flat part with respect to a mesa space | interval. The difference between the etching depth in the flat portion and the etching depth in the element gap portion of the surface emitting laser element and the etching depth in the flat portion when etching is stopped at the reflective layer arranged on the substrate side is shown with respect to the mesa interval. FIG. It is the top view and sectional drawing of a surface emitting laser array shown in FIG. FIG. 6 is another plan view of the surface emitting laser array according to the first embodiment. 6 is a plan view of a surface emitting laser array according to a second embodiment. FIG. It is a schematic sectional drawing of the surface emitting laser element shown in FIG. It is sectional drawing which shows the vicinity of the active layer of the surface emitting laser element shown in FIG. It is sectional drawing of the surface emitting laser element by Embodiment 2 used for experiment. It is sectional drawing of the surface emitting laser element for a comparison used for experiment. It is a related figure of the optical output and electric current which show an experimental result. 6 is a plan view of a surface emitting laser array according to Embodiment 3. FIG. FIGS. 21A to 21D are views (No. 1) for describing the method of manufacturing the surface emitting laser array according to the fourth embodiment. FIGS. 22A to 22D are views (No. 2) for describing the method of manufacturing the surface emitting laser array according to the fourth embodiment. FIG. 13 is a view (No. 3) for explaining the method of manufacturing the surface emitting laser array of the fourth embodiment. FIG. 10 is a diagram for explaining a surface emitting laser array according to a fourth embodiment. It is the schematic which shows the structure of the optical scanning device using the surface emitting laser array shown in FIG. It is the schematic of a laser printer. 1 is a schematic diagram of an image forming apparatus. It is the schematic of an optical transmission module. It is a top view of the conventional surface emitting laser array.

  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 plan view of a surface emitting laser array according to Embodiment 1 of the present invention. Referring to FIG. 1, surface emitting laser array 100 according to the first embodiment includes surface emitting laser elements 1 to 32, pads 51 to 82, and wires W1 to W32.

  The surface emitting laser elements 1 to 32 are two-dimensionally arranged in 4 rows × 8 columns. Each of the surface emitting laser elements 1 to 32 has a rectangular shape with one side of 16 μm. And four surface emitting laser elements 1, 9, 17, 25/2, 10, 18, 26/3, 11, 19, 27/4, 12, 20, 28/5, 13, 21, 29/6 , 14, 22, 30/7, 15, 23, 31/8, 16, 24, 32 are arranged in the sub-scanning direction, and the eight surface emitting laser elements 1-8 / 9-16 / 17-24 / 25 to 32 are arranged in the main scanning direction.

  The eight surface emitting laser elements 1 to 8/9 to 16/17 to 24/25 to 32 arranged in the main scanning direction are arranged stepwise in the sub scanning direction. As a result, the 32 laser beams emitted from the 32 surface emitting laser elements 1 to 32 do not overlap each other.

  In the eight surface emitting laser elements 1 to 8/9 to 16/17 to 24/25 to 32 arranged in the main scanning direction, the interval between two adjacent surface emitting laser elements is set to an interval X. .

  Also, four surface emitting laser elements 1, 9, 17, 25/2, 10, 18, 26/3, 11, 19, 27/4, 12, 20, 28/5 arranged in the sub-scanning direction. In 13, 21, 29/6, 14, 22, 30/7, 15, 23, 31/8, 16, 24, and 32, the interval between two adjacent surface emitting laser elements is set to the interval d. . The interval d is narrower than the interval X. For example, the interval d is set to 24 μm, and the interval X is set to 30 μm.

  The intervals c1 in the sub-scanning direction of the eight perpendicular lines drawn from the eight centers of the eight surface emitting laser elements 1 to 8 arranged in the main scanning direction to straight lines arranged in the sub-scanning direction are equal intervals. Yes, determined by c1 = d / 8. When the distance d is set to 24 μm, the distance c1 is 24/8 = 3 μm.

  Sub-scanning direction of eight perpendicular lines drawn from eight centers of eight surface emitting laser elements 9 to 16/17 to 24/25 to 32 arranged in the main scanning direction into straight lines arranged in the sub-scanning direction The intervals at are also equal intervals and are the same as the interval c1.

  The pads 51 to 82 are arranged around the surface emitting laser elements 1 to 32 arranged two-dimensionally. Wires W1 to W32 connect the surface emitting laser elements 1 to 32 to the pads 51 to 82, respectively. Each of the wires W1 to W32 has a line width of 8 μm, for example.

  Of the surface emitting laser elements 1 to 32 arranged two-dimensionally, the surface emitting laser elements 1 to 8, 9, 16, 17, 24 to 32 arranged on the outermost periphery are respectively connected to pads 51 to 59, 66, 67, Wires W1 to W9, S16, W17, and W24 to W32 connected to 74 and 75 to 82 are arranged without passing between two adjacent surface emitting laser elements.

  Of the surface-emitting laser elements 1 to 32 arranged two-dimensionally, wires that connect the surface-emitting laser elements 10 to 15 and 18 to 23 disposed on the inner periphery to the pads 60 to 65 and 68 to 73, respectively. W10 to W15 and W18 to W23 are arranged so as to pass between two surface emitting laser elements adjacent in the main scanning direction. As described above, in the eight surface emitting laser elements 1 to 8/9 to 16/17 to 24/25 to 32 arranged in the main scanning direction, the interval between two adjacent surface emitting laser elements is an interval. Since each of the surface emitting laser elements 1 to 32 is set to X (= 30 μm) and has a rectangular shape with one side of 16 μm, the distance between two surface emitting laser elements adjacent in the main scanning direction is 30-16 = Wires W10 to W15 and W18 to W23 having a line width of 14 μm and a line width of 8 μm can be arranged between two surface emitting laser elements adjacent in the main scanning direction.

FIG. 2 is a schematic cross-sectional view of the surface emitting laser element 1 shown in FIG. Referring to FIG. 2, the surface emitting laser element 1 includes a substrate 101, reflection layers 102 and 106, resonator spacer layers 103 and 105, an active layer 104, a selective oxidation layer 107, a contact layer 108, A SiO ₂ layer 109, an insulating resin 110, a p-side electrode 111, and an n-side electrode 112 are provided. The surface-emitting laser element 1 is a surface-emitting laser that emits laser light in the 780 nm band.

The substrate 101 is made of n-type gallium arsenide (n-GaAs). Reflective layer 102, when a one cycle pairs _{n-AlAs / n-Al 0.3} Ga 0.7 As, 40.5 periods _{[n-AlAs / n-Al} 0.3 Ga 0.7 As And is formed on one main surface of the substrate 101. The film thickness of each of n-AlAs and n-Al _0.3 Ga _0.7 As is λ / 4n where n is the oscillation wavelength of the surface emitting laser element 1 (n is the refractive index of each semiconductor layer) ).

The resonator spacer layer 103 is made of non-doped (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P, and is formed on the reflective layer 102. The active layer 104 has a quantum well structure including a well layer made of GaInPAs and a barrier layer made of Ga _0.6 In _0.4 P, and is formed on the resonator spacer layer 103.

The resonator spacer layer 105 is made of non-doped (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P and is formed on the active layer 104. The reflective layer 106 has [p-Al _0.9 Ga _0.1 As of 24 periods when a pair of p-Al _0.9 Ga _0.1 As / Al _0.3 Ga _0.7 As is taken as one period. / Al _0.3 Ga _0.7 As] and formed on the resonator spacer layer 105. The film thickness of each of p-Al _0.9 Ga _0.1 As and Al _0.3 Ga _0.7 As is λ / 4n (n is the refractive index of each semiconductor layer).

  The selective oxidation layer 107 is made of p-AlAs and is provided in the reflection layer 106. More specifically, the selective oxidation layer 107 is provided at a position 7λ / 4 from the resonator spacer layer 105. The selective oxidation layer 107 includes a non-oxidized region 107a and an oxidized region 107b, and has a thickness of 20 nm.

The contact layer 108 is made of p-GaAs and is formed on the reflective layer 106. The SiO ₂ layer 109 is formed so as to cover one main surface of a part of the resonator spacer layer 103 and the end surfaces of the active layer 104, the resonator spacer layer 105, the reflective layer 106, the selective oxidation layer 107, and the contact layer 108. Is done.

The insulating resin 110 is formed in contact with the SiO ₂ layer 109. The p-side electrode 111 is formed on part of the contact layer 108 and the insulating resin 110. The n-side electrode 112 is formed on the back surface of the substrate 101.

  Each of the reflective layers 102 and 106 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 oxidized region 107b has a smaller refractive index than the non-oxidized region 107a. The oxidized region 107b constitutes a current confinement part that restricts the path through which the current injected from the p-side electrode 111 flows to the active layer 104 to the non-oxidized region 107a, and also oscillates the oscillation light oscillated in the active layer 104. Confine in the region 107a. Thus, the surface emitting laser element 1 can oscillate with a low threshold current. As described above, the current confinement portion is produced by selectively oxidizing the oxidized region 107b of the selective oxidation layer 107. Therefore, the current confinement part is a selective oxidation type.

FIG. 3 is a sectional view showing the vicinity of the active layer 104 of the surface emitting laser element 1 shown in FIG. Referring to FIG. 3, the reflective layer 102 includes a low refractive index layer 1021, a high refractive index layer 1022, and a composition gradient layer 1023. The low refractive index layer 1021 is made of n-AlAs, and the high refractive index layer 1022 is made of n-Al _0.3 Ga _0.7 As. The composition gradient layer 1023 is made of n-AlGaAs in which the Al composition gradually changes from one of the low refractive index layer 1021 and the high refractive index layer 1022 to the other. The low refractive index layer 1021 is in contact with the resonator spacer layer 103.

The reflective layer 106 includes a low refractive index layer 1061, a high refractive index layer 1062, and a composition gradient layer 1063. The low refractive index layer 1061 is made of p-Al _0.9 Ga _0.1 As, and the high refractive index layer 1062 is made of p-Al _0.3 Ga _0.7 As. The composition gradient layer 1063 is made of p-AlGaAs in which the Al composition gradually changes from one of the low refractive index layer 1061 and the high refractive index layer 1062 to the other. The low refractive index layer 1061 is in contact with the resonator spacer layer 105.

The active layer 104 has a quantum well structure in which three well layers 1041 each made of GaInPAs and four barrier layers 1042 each made of Ga _0.6 In _0.4 P are alternately stacked. The barrier layer 1042 is in contact with the resonator spacer layers 103 and 105. GaInPAs constituting the well layer 1041 has a compressive strain composition, and Ga _0.6 In _0.4 P constituting the barrier layer 1042 has a tensile strain.

  In the surface emitting laser element 1, the resonator spacer layers 103 and 105 and the active layer 104 constitute a resonator, and the thickness of the resonator in the direction perpendicular to the substrate 101 is equal to one wavelength of the surface emitting laser element 1 ( = Λ). That is, the resonator spacer layers 103 and 105 and the active layer 104 constitute a one-wavelength resonator.

  Each of the surface emitting laser elements 2 to 32 shown in FIG. 1 has the same configuration as that of the surface emitting laser element 1 shown in FIGS.

  4, 5 and 6 are first to third process diagrams showing a method of manufacturing the surface emitting laser array 100 shown in FIG. In the description of FIG. 4 to FIG. 6, refer to the process of manufacturing four surface emitting laser elements 1, 9, 17, and 25 among the 32 surface emitting laser elements 1 to 32 shown in FIG. 1. A method for manufacturing the surface emitting laser array 100 will now be described.

  Referring to FIG. 4, 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 vessel spacer layer 105, a reflective layer 106, a selective oxidation layer 107, and a contact layer 108 are sequentially stacked on the substrate 101 (see step (a) in FIG. 4).

In this case, n-AlAs and n-Al _0.3 Ga _0.7 As of the reflective layer 102 are changed to trimethylaluminum (TMA), trimethylgallium (TMG), arsine (AsH ₃ ), and hydrogen selenide (H ₂ Se). As a raw material, (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P of the resonator spacer layer 103 is changed from trimethylaluminum (TMA), trimethylgallium (TMG), trimethylindium (TMI), and phosphine ( PH ₃ ) is used as a raw material.

Further, GaInPAs of the active layer 104 is formed using trimethylgallium (TMG), trimethylindium (TMI), phosphine (PH ₃ ), and arsine (AsH ₃ ) as raw materials, and Ga _0.6 In _0.4 P of the active layer 104 is formed. From trimethylgallium (TMG), trimethylindium (TMI) and phosphine (PH ₃ ).

Further, (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P of the resonator spacer layer 105 is changed from trimethylaluminum (TMA), trimethylgallium (TMG), trimethylindium (TMI), and phosphine (PH ₃ ). Is used as a raw material.

_{Further, p-Al 0.9 Ga 0.1 As} / p-Al 0.3 Ga 0.7 As trimethylaluminum reflective layer 106 (TMA), trimethyl gallium (TMG), arsine (AsH ₃₎ and tetrabromide Carbonized carbon (CBr ₄ ) is used as a raw material. Note that dimethyl zinc (DMZn) may be used instead of carbon tetrabromide (CBr ₄ ).

Further, p-AlAs for the selective oxidation layer 107 is formed using trimethylaluminum (TMA), arsine (AsH ₃ ), and carbon tetrabromide (CBr ₄ ) as raw materials, and p-GaAs for the contact layer 108 is trimethylgallium (TMG). , Arsine (AsH ₃ ) and carbon tetrabromide (CBr ₄ ). Also in this case, dimethyl zinc (DMZn) may be used instead of carbon tetrabromide (CBr ₄ ).

  Thereafter, a resist is applied on the contact layer 108, and a resist pattern 120 is formed on the contact layer 108 using a photoengraving technique (see step (b) in FIG. 4).

  When the resist pattern 120 is formed, using the formed resist pattern 120 as a mask, a part of the resonator spacer layer 103, the active layer 104, the resonator spacer layer 105, the reflective layer 106, the selective oxidation layer 107, and the contact layer 108 are formed. Then, the resist pattern 120 is removed.

In this case, part of the resonator spacer layer 103, the active layer 104, the cavity spacer layer 105, the reflective layer 106, the selective oxidation layer 107 and the contact layer _{108, Cl 2, BCl 3, SiCl} 4, CCl 4, CF 4 Reactive ion beam etching (RIBE), inductively coupled plasma (ICP) etching, reactive ion etching (RIE), and the like are introduced by introducing a halogen-based gas such as a reactive ion beam etching method (RIBE: Reactive Ion Beam Etching). Etching is performed by a dry etching method using plasma. During etching of a part of the resonator spacer layer 103, the active layer 104, the resonator spacer layer 105, the reflective layer 106, the selective oxidation layer 107, and the contact layer 108, plasma emission spectroscopy is performed from the viewing window of the etching apparatus. The time change of the emission intensity of 451 nm is monitored. Since the emission of In can be detected only when the resonator region is etched, the etching can be easily stopped in the resonator region made of an AlGaInPAs-based material.

  As a result, the mesa structures 131 to 134 in the surface emitting laser elements 1, 9, 17 and 25 are formed (see step (c) in FIG. 4). Each of the mesa structures 131 to 134 includes a part of the resonator spacer layer 103, the active layer 104, the resonator spacer layer 105, the reflective layer 106, the selective oxidation layer 107, and the contact layer 108.

  A part of the resonator spacer layer 103, the active layer 104, the resonator spacer layer 105, the reflective layer 106, the selective oxidation layer 107, and the contact layer 108 may be etched by wet etching. When the reflective layer 106 made of an AlGaAs-based material, the selective oxidation layer 107, and the contact layer 108 are selectively etched by wet etching, a sulfuric acid-based etchant can be used.

  Next, referring to FIG. 5, after the step (c) shown in FIG. 4, the sample is heated to 350 ° C. in an atmosphere in which water heated to 85 ° C. is bubbled with nitrogen gas, thereby selectively oxidizing layer 107. Is oxidized from the outer peripheral portion toward the central portion to form a non-oxidized region 107a and an oxidized region 107b in the selective oxidation layer 107 (see step (d) in FIG. 5).

Thereafter, a SiO ₂ layer 109 is formed on the entire surface of the sample by using a chemical vapor deposition (CVD) method, and a region serving as a light emitting portion and a surrounding SiO ₂ layer using a photoengraving technique. 109 is removed (see step (e) in FIG. 5).

  Next, the insulating resin 110 is applied to the entire sample by spin coating, and the insulating resin 110 on the region to be the light emitting portion is removed (see step (f) in FIG. 5).

  Referring to FIG. 6, after forming insulating resin 110, a resist pattern having a predetermined size is formed on a region serving as a light emitting portion, and a p-side electrode material is formed on the entire surface of the sample by vapor deposition. The p-side electrode material on the pattern is removed by lift-off to form the p-side electrode 111 (see step (g) in FIG. 6). Then, the back surface of the substrate 101 is polished, an n-side electrode 112 is formed on the back surface of the substrate 101, and further annealed to establish ohmic conduction between the p-side electrode 111 and the n-side electrode 112 (step (h) in FIG. 6). reference). Thereby, the surface emitting laser array 100 is completed.

  Note that, in steps (b) and (c) shown in FIG. 4, dry etching for forming four surface emitting laser elements is shown, but actually, steps (b) and (c) In FIG. 1, dry etching is performed to simultaneously form the 32 surface emitting laser elements 1 to 32 shown in FIG. In this case, the resist pattern for simultaneously forming the 32 surface emitting laser elements 1 to 32 is formed using a photomask suitable for the arrangement of the 32 surface emitting laser elements 1 to 32 shown in FIG. . That is, the resist pattern for simultaneously forming the 32 surface emitting laser elements 1 to 32 is set so that the distances X and d satisfy d <X, and the eight surfaces are arranged in the main scanning direction. Designed so that eight perpendicular lines dropped from eight centers of the light emitting laser elements 1 to 8/9 to 16/17 to 24/25 to 32 in a straight line arranged in the sub-scanning direction are equally spaced c1. It is formed using a photomask.

  In the surface emitting laser array 100, the interval d between the surface emitting laser elements arranged in the sub-scanning direction is set smaller than the interval X between the surface emitting laser elements arranged in the main scanning direction. Thereby, the interval c1 (= d / 8) can be made smaller than when the interval d is larger than the interval X, which is advantageous for high-density recording.

  Although it is possible to reduce both the interval between the surface emitting laser elements arranged in the sub-scanning direction and the interval between the surface emitting laser elements arranged in the main scanning direction, the influence of thermal interference between the elements can be reduced, Since it is necessary to widen at least one of the intervals in order to secure a space necessary for passing the element wiring, it is preferable to widen the main scanning direction in order to perform high-density writing.

  FIG. 7 is a diagram for explaining the etching in FIG. 4B in detail. FIG. 7 shows a case where the crystal layer formed of the resonator spacer layer 103, the active layer 104, the resonator spacer layer 105, the reflective layer 106, the selective oxidation layer 107, and the contact layer 108 is etched without using the resist pattern 120. The distribution of the etching depth in the in-plane direction DR1 of the substrate 101 is shown.

  Referring to FIG. 7, the distribution of the etching depth in the in-plane direction DR1 of substrate 101 when etching contact layer 108, selective oxide layer 107, and reflective layer 106 (referred to as "region REG1") is a curve k1. Represented by In addition, the etching depth distribution in the in-plane direction DR1 of the substrate 101 when the resonator spacer layer 105, the active layer 104, and the resonator spacer layer 103 (referred to as "region REG2") are etched is represented by a curve k2. Is done.

  As described above, the reflective layer 106, the selective oxidation layer 107, and the contact layer 108 are made of an AlGaAs-based material. Therefore, the etching rate is relatively fast, and the distribution of the etching depth DR1 in the region REG1 is as follows. It becomes relatively large (see curve k1).

  On the other hand, since the cavity spacer layers 103 and 105 and the active layer 104 contain In and the vapor pressure of the reaction product of In is low, the etching rates of the cavity spacer layers 103 and 105 and the active layer 104 are as follows. The etching rate is slower than the etching rate of the selective oxidation layer 107 and the contact layer 108, and the distribution of the etching depth in the region REG2 in the in-plane direction DR1 is smaller than the distribution of the etching depth in the region REG1 in the in-plane direction DR1 (curve). k2). That is, the difference in the etching depth in the in-plane direction DR1 generated in the region REG1 is absorbed by the slow etching rate in the region REG2. As a result, the distribution of the etching depth in the in-plane direction DR1 in the region REG2 is smaller than the distribution of the etching depth in the region REG1 in the in-plane direction DR1.

  An experimental result indicating that the etching rate in the region REG2 containing In is slower than the etching rate in the region REG1 made of an AlGaAs-based material will be described. FIGS. 8 and 9 are first and second timing charts of plasma emission during etching when the surface-emitting laser array 100 shown in FIG. 1 is manufactured, respectively.

  8 and 9, the vertical axis represents the intensity of plasma emission, and the horizontal axis represents time. FIG. 8 shows a case where etching is performed halfway in the resonator region, and FIG. 9 shows a case where etching is performed from the resonator region to about the third pair of the reflective layer 102. Further, in FIG. 8, a curve k3 indicates the emission intensity of gallium (Ga), a curve k4 indicates the emission intensity of indium (In), and a curve k5 indicates the emission intensity of aluminum (Al). Further, in FIG. 9, a curve k6 indicates the emission intensity of Ga, a curve k7 indicates the emission intensity of In, and a curve k8 indicates the emission intensity of Al. Further, in the experiment, a sample was used in which the thickness from the surface to the interface between the reflective layer 106 and the resonator region was 3.18 μm, and the thickness of the resonator region containing In was 0.23 μm.

The etching rate in the region from the surface to the interface between the reflective layer 106 and the resonator region is 3.18 μm / 871 sec = 3.65 × 10 ⁻³ μm / sec. On the other hand, the etching rate in the resonator region is 0.23 μm / 372 sec = 6.18 × 10 ⁻⁴ μm / sec (see FIG. 9).

  As described above, in the resonator region containing In, the etching rate is decreased, and the film thickness of the resonator region (= 0.23 μm) is changed to the film thickness (= 3.18 μm) of the region above the resonator region. Although it is relatively thin, it takes a long time to etch the entire resonator region.

  The emission intensity of In increases in the resonator region (see curves k4 and k7). Therefore, the etching can be easily stopped in the resonator region by detecting that the In emission intensity has increased.

  The emission intensity of Ga and the emission intensity of Al periodically change as the etching time elapses, and the amplitude of the emission intensity gradually decreases as the etching time elapses (see curves k3, k5, k6, and k8).

  If the etching depth distribution in the in-plane direction DR1 of the wafer is uniform, the Ga emission intensity and the Al emission intensity change periodically with a substantially constant amplitude. On the other hand, if the etching depth distribution in the in-plane direction DR1 of the wafer is non-uniform, the light emission of Al and the light emission of Ga are observed at the same time. Becomes smaller.

  Accordingly, the fact that the amplitude of Ga emission intensity and the amplitude of Al emission intensity are gradually reduced with the lapse of etching time means that the etching depth in the in-plane direction DR1 of the wafer varies with the lapse of etching time. Means that

  After the etching penetrates the resonator region, the amplitude of the Ga emission intensity and the amplitude of the Al emission intensity are further reduced. Therefore, when the etching bottom reaches the reflective layer 102, the in-plane is reached. An even greater difference occurs in the etching depth in the direction DR1 (see curves k6 and k8).

  FIG. 10 is a diagram showing the difference between the etching depth in the flat portion and the etching depth in the element gap portion of the surface emitting laser element and the etching depth in the flat portion with respect to the mesa interval when etching is stopped in the resonator region. It is. Further, FIG. 11 shows the etching depth in the flat portion and the etching depth in the element gap portion of the surface emitting laser element and the etching depth in the flat portion when etching is stopped at the reflective layer 102 disposed on the substrate 101 side. It is a figure which shows a difference with respect to a mesa space | interval.

  10 and 11, the vertical axis represents the etching depth of the flat portion and the difference Δd between the etching depth in the element gap portion and the etching depth in the flat portion, and the horizontal axis represents the mesa interval. In FIGS. 10 and 11, ♦ indicates the flat portion etching depth, and ■ indicates the difference Δd.

  When etching is stopped in the middle of the resonator region, even if the mesa interval is 10 μm or less, the difference Δd between the etching depth between the surface emitting laser elements and the etching depth at the flat portion is 100 nm or less (FIG. 10). reference).

  On the other hand, when etching is stopped at the reflective layer 102 provided on the substrate 101 side, when the mesa interval is about 23 μm, the difference Δd is 100 nm, and when the mesa interval is 20 μm or less, the difference Δd is less than 100 nm. Also grows. When the mesa interval is 10 μm or less, the difference Δd increases to about 250 nm (see FIG. 11).

  Thus, by stopping etching in the resonator region containing In, even if there is a large difference in the etching depth between the element gap portion and the flat portion up to the resonator region, the etching depth is reduced. The large difference is absorbed in the resonator region where the etching rate is low, and the difference Δd between the etching depth in the element gap portion and the etching depth in the flat portion can be reduced even if the mesa interval is reduced. That is, by stopping etching in the resonator region containing In, the surface of the wafer on which there are an element gap portion in which a plurality of surface emitting laser elements 1 to 32 are dense and a flat portion where no surface emitting laser element is formed exist. The etching depth in the inward direction DR1 can be made uniform.

  12 is a plan view and a cross-sectional view of the surface emitting laser array 100 shown in FIG. Referring to FIG. 12, the region where surface emitting laser elements 1 to 32 are disposed is a non-etched region, and the periphery of surface emitting laser devices 1 to 32 is an etched region. The cross-sectional view between A and A ′ is a cross-sectional view of the flat portion around the surface emitting laser elements 25 to 27 and the surface emitting laser element 25. The etching depth between the surface emitting laser elements 25 and 26 and between the surface emitting laser elements 26 and 27 is D1, and the etching depth in the flat portion around the surface emitting laser element 25 is D2. The etching depth D1 is shallower than the etching depth D2. As a result, the difference between the etching depth D1 and the etching depth D2 is Δd.

  Etching the contact layer 108, the selective oxidation layer 107, the reflection layer 106, the resonator spacer layer 105, the active layer 104 and the resonator spacer layer 103 forms the tails 141 to 145, but the resonator spacer layer 103 , 105 and the active layer 104 contain In and have a relatively slow etching rate, as described above, and therefore the in-plane direction DR1 of the surface emitting laser array 100 when the cavity spacer layers 103 and 105 and the active layer 104 are etched. Etching also proceeds. As a result, the size of the tails 141 to 145 is smaller than that of the conventional surface emitting laser array.

  In the etched shape of the skirt portion, the slope and the slope of the upper side of the mesa structure are different, and when the etched shape of the skirt portion includes an oxide constriction layer, the width of the selectively oxidized layer is the upper portion of the mesa structure. Therefore, it is difficult to accurately estimate the width of the selective oxidation layer. As a result, the estimation of the width of the oxidized region 107b becomes inaccurate, and it becomes difficult to accurately control the oxidized constriction diameter. Therefore, it is preferable that the etching bottom face enter the resonator region throughout the entire array chip.

  When the thickness of the resonator region is λ (single wavelength resonator thickness), it is possible to perform the etching so that the center in the thickness direction of the resonator region becomes the etching bottom surface (flat portion). In this case, Δd may be λ / 2 or less as an effective length in the medium. Since the oscillation wavelength of the surface emitting laser elements 1 to 32 in the first embodiment is 780 nm, the thickness of the one-wavelength resonator is about 230 nm. As a result, Δd is preferably 115 nm or less.

  In the conventional surface emitting laser array, when the difference Δd is 115 nm, the mesa interval is about 20 μm (see FIG. 11). In the surface emitting laser array 100 according to the present invention, the mesa interval is 20 μm or less. However, the difference Δd is smaller than 100 nm. Therefore, the present invention is particularly effective when the mesa interval is 20 μm or less. Note that when the wavelength is shorter than 780 nm, the thickness of the one-wavelength resonator is reduced, so that Δd exceeds λ / 2 in a region where the mesa interval is wider.

  As described above, in the surface emitting laser array 100, mesa etching for forming the mesa structure is stopped in the middle of the resonator region containing In (= in the middle of the resonator spacer layer 103). Even if the interval is reduced, the difference Δd between the etching depth in the element gap and the etching depth in the flat portion is reduced, and the low refractive index layer (= AlAs) of the reflective layer 102 is not exposed in the flat portion. As a result, even if the selective oxidation layer 107 is selectively oxidized, the low refractive index layer (= AlAs) of the reflective layer 102 is not oxidized.

  Therefore, according to the present invention, heat generated in the active layer 104 can be released to the substrate 1 through the AlAs (low refractive index layer) of the reflective layer 102, and heat can be transferred to the active layer 104 without using a dummy element. It can be hard to hang up.

  The interval between two surface emitting laser elements adjacent in the element gap is the distance between the surface emitting laser elements at the top surface position of the mesa structure and the space between the surface emitting laser elements at the bottom surface position of the mesa structure. Say the narrower spacing. Depending on the etching method for forming the mesa structure, the distance between the surface emitting laser elements at the top surface position of the mesa structure is larger, or the distance between the surface emitting laser elements at the bottom surface position of the mesa structure is larger. Because it becomes wider.

  FIG. 13 is another plan view of the surface emitting laser array according to the first embodiment. The surface emitting laser array according to the first embodiment may be a surface emitting laser array 100A shown in FIG. Referring to FIG. 13, surface emitting laser array 100A is obtained by adding surface emitting laser elements 33 to 40, pads 83 to 90, and wires W33 to W40 to surface emitting laser array 100 shown in FIG. The others are the same as those of the surface emitting laser array 100.

  In the surface emitting laser array 100A, the surface emitting laser elements 1 to 40 are two-dimensionally arranged in 4 rows × 10 columns. Each of the surface emitting laser elements 33 to 40 has a rectangular shape with one side of 16 μm, like each of the surface emitting laser elements 1 to 32. And four surface emitting laser elements 1, 11, 21, 31/2, 12, 22, 32/3, 13, 23, 33/4, 14, 24, 34/5, 15, 25, 35/6 , 16, 26, 36/7, 17, 27, 37/8, 18, 28, 38/9, 19, 29, 39/10, 20, 30, 40 are arranged in the sub-scanning direction. The surface emitting laser elements 1 to 10/11 to 20/21 to 30/31 to 40 are arranged in the main scanning direction.

  Ten surface emitting laser elements 1 to 10/11 to 20/21 to 30/31 to 40 arranged in the main scanning direction are arranged stepwise in the sub scanning direction. As a result, the 40 laser beams emitted from the 40 surface emitting laser elements 1 to 40 do not overlap each other.

  In 10 surface emitting laser elements 1 to 10/11 to 20/21 to 30/31 to 40 arranged in the main scanning direction, the interval between two adjacent surface emitting laser elements is set to an interval X. .

  The four surface emitting laser elements 1, 11, 21, 31/2, 12, 22, 32/3, 13, 23, 33/4, 14, 24, 34/5, which are arranged in the sub-scanning direction. 15, 25, 35/6, 16, 26, 36/7, 17, 27, 37/8, 18, 28, 38/9, 19, 29, 39/10, 20, 30, 40, adjacent 2 The interval between the two surface emitting laser elements is set to the interval d.

  Intervals c2 in the sub-scanning direction of 10 perpendicular lines drawn from 10 centers of the 10 surface emitting laser elements 1 to 10 arranged in the main scanning direction to straight lines arranged in the sub-scanning direction are equal intervals. Yes, determined by c2 = d / 10. When the distance d is set to 24 μm, the distance c2 is 24/10 = 2.4 μm.

  Sub-scanning direction of 10 perpendicular lines drawn down from 10 centers of 10 surface emitting laser elements 11 to 20/21 to 30/31 to 40 arranged in the main scanning direction into straight lines arranged in the sub-scanning direction The intervals at are also equal and are the same as the interval c2.

  The pads 51 to 90 are arranged around the surface emitting laser elements 1 to 40 arranged two-dimensionally. Wires W1 to W40 connect the surface emitting laser elements 1 to 40 to the pads 51 to 90, respectively. Each of the wires W33 to W40 has a line width of 8 μm, for example.

  Among the surface emitting laser elements 1 to 40 arranged two-dimensionally, the surface emitting laser elements 1 to 11, 20, 21, and 30 to 40 arranged on the outermost periphery are respectively pads 51 to 61, 70, 71, and 80 to 80. Wires W1 to W11, W20, W21, and W30 to W40 connected to 90 are arranged without passing between two adjacent surface emitting laser elements.

  Of the surface emitting laser elements 1 to 40 arranged two-dimensionally, wires for connecting the surface emitting laser elements 12 to 19 and 22 to 29 arranged on the inner periphery to the pads 62 to 69 and 72 to 79, respectively. W12 to W19 and W22 to W29 are arranged so as to pass between two surface emitting laser elements adjacent in the main scanning direction. As described above, if the line width of the wires W1 to W40 is 8 μm, each of the wires W12 to W19 and W22 to W29 can be disposed between two surface emitting laser elements adjacent in the main scanning direction. is there.

  Further, the epitaxial layer remains in the region where the pads 51 to 90 are disposed, the groove 150 is formed around the surface emitting laser elements 1 to 40, and the groove 150 is buried with polyimide. The wiring passes over the polyimide. Further, the pads 51 to 90 are bonded to the epitaxial layer through an insulating film. The adhesion between the pads 1 to 40 and the insulating film can be made stronger than the formation of the pads 1 to 40 on the polyimide, and the pad peeling at the time of wire bonding can be reliably prevented.

  Each of the surface-emitting laser elements 33 to 40 has the same cross-sectional structure as that of the surface-emitting laser element 1 shown in FIGS. 2 and 3. Accordingly, also in the surface emitting laser array 100A, the mesa etching for forming the mesa structure is stopped in the middle of the resonator region containing In (= in the middle of the resonator spacer layer 103), so the mesa interval is small. Even in this case, the difference Δd between the etching depth in the element gap and the etching depth in the flat portion becomes small, and the low refractive index layer (= AlAs) of the reflective layer 102 is not exposed in the flat portion. As a result, even if the selective oxidation layer 107 is selectively oxidized, the low refractive index layer (= AlAs) of the reflective layer 102 is not oxidized.

  Therefore, according to the present invention, heat generated in the active layer 104 can be released to the substrate 1 through the AlAs (low refractive index layer) of the reflective layer 102, and heat can be transferred to the active layer 104 without using a dummy element. It can be hard to hang up.

[Embodiment 2]
FIG. 14 is a plan view of the surface emitting laser array according to the second embodiment. Referring to FIG. 14, surface emitting laser array 200 according to the second embodiment is obtained by replacing surface emitting laser elements 1 to 32 of surface emitting laser array 100 shown in FIG. 1 with surface emitting laser elements 151 to 182. The others are the same as those of the surface emitting laser array 100. In the surface emitting laser array 200, the wires W1 to W32 connect the surface emitting laser elements 151 to 182 to the pads 51 to 82, respectively.

  The surface emitting laser elements 151 to 182 are arranged two-dimensionally in 4 rows × 8 columns. Each of the surface emitting laser elements 151 to 182 has a rectangular shape with one side of 16 μm. The four surface emitting laser elements 151, 159, 167, 175/152, 160, 168, 176/153, 161, 169, 177/154, 162, 170, 178/155, 163, 171, 179/156 , 164, 172, 180/157, 165, 173, 181/158, 166, 174, and 182 are arranged in the sub-scanning direction, and the eight surface emitting laser elements 151 to 158/159 to 166/167 to 174 / 175 to 182 are arranged in the main scanning direction.

  The eight surface emitting laser elements 151 to 158/159 to 166/167 to 174/175 to 182 arranged in the main scanning direction are arranged stepwise in the sub scanning direction. As a result, the 32 laser beams emitted from the 32 surface emitting laser elements 1 to 32 do not overlap each other.

  In the eight surface emitting laser elements 151 to 158/159 to 166/167 to 174/175 to 182 arranged in the main scanning direction, the interval between two adjacent surface emitting laser elements is set to an interval X. .

  Also, four surface emitting laser elements 151, 159, 167, 175/152, 160, 168, 176/153, 161, 169, 177/154, 162, 170, 178/155 arranged in the sub-scanning direction. In 163, 171, 179/156, 164, 172, 180/157, 165, 173, 181/158, 166, 174, and 182, the interval between two adjacent surface emitting laser elements is set to the interval d. .

  The intervals in the sub-scanning direction of the eight perpendicular lines drawn from the eight centers of the eight surface emitting laser elements 151 to 158 arranged in the main scanning direction to the straight line arranged in the sub-scanning direction are equal intervals. , The interval c1 is set.

  Sub-scanning direction of eight perpendicular lines drawn from eight centers of the eight surface emitting laser elements 159 to 166/167 to 174/175 to 182 arranged in the main scanning direction into straight lines arranged in the sub-scanning direction The interval at is also equal and is set to the interval c1.

  FIG. 15 is a schematic cross-sectional view of the surface emitting laser element 151 shown in FIG. Referring to FIG. 15, in surface emitting laser element 151, resonator spacer layers 103 and 105 and reflecting layer 106 of surface emitting laser element 1 shown in FIG. 2 are replaced with resonator spacer layers 103A and 105A and reflecting layer 106A, respectively. The others are the same as those of the surface emitting laser element 1.

The resonator spacer layer 103 _</ b> A is made of non-doped (Al _0.1 Ga _0.9 ) _0.5 In _0.5 P, and is formed on the reflective layer 102. The resonator spacer layer 105 _</ b> A is made of non-doped (Al _0.1 Ga _0.9 ) _0.5 In _0.5 P and is formed on the active layer 104.

The reflective layer 106A is composed of p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P in the low refractive index layer closest to the active layer 104 among the reflective layers 106 shown in FIG. And formed on the resonator spacer layer 105A. The reflective layer 106A constitutes a semiconductor distributed Bragg reflector that confines the oscillation light oscillated in the active layer 104 by Bragg multiple reflection and confines it in the active layer 104.

FIG. 16 is a cross-sectional view showing the vicinity of the active layer 104 of the surface emitting laser element 151 shown in FIG. Referring to FIG. 16, the low refractive index layer 1021 of the reflective layer 102 is in contact with the resonator spacer layer 103A. The resonator spacer layer 103 </ b> A is in contact with the low refractive index layer 1021 of the reflective layer 102 and the barrier layer 1042 of the active layer 104. The reflective layer 106A is the same as the reflective layer 106 except that the low refractive index layer 1061 closest to the active layer 104 is replaced with the low refractive index layer 1061A in the reflective layer 106 shown in FIG. The low refractive index layer 1061A is made of p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P and is in contact with the resonator spacer layer 105A. The resonator spacer layer 105A is in contact with the barrier layer 1042 of the active layer 104 and the low refractive index layer 1061A of the reflective layer 106A.

  In the surface emitting laser element 151, the resonator spacer layers 103 A and 105 A and the active layer 104 constitute a resonator, and the thickness of the resonator in the direction perpendicular to the substrate 101 is equal to one wavelength of the surface emitting laser element 151 ( = Λ). That is, the resonator spacer layers 103A and 105A and the active layer 104 constitute a one-wavelength resonator.

  Each of surface emitting laser elements 152 to 182 shown in FIG. 14 has the same configuration as that of surface emitting laser element 151 shown in FIGS. 15 and 16.

The surface emitting laser array 200 is manufactured according to steps (a) to (h) shown in FIGS. 4, 5, and 6. In this case, in step (a) of FIG. 4, (Al _0.1 Ga _0.9 ) _0.5 In _0.5 P of the resonator spacer layers 103A and 105A is trimethylaluminum (TMA) using MOCVD. ), Trimethylgallium (TMG), trimethylindium (TMI), and phosphine (PH ₃ ) as raw materials, and p- (Al _0.7 Ga _0.3 ) ₀ constituting the low refractive index layer 1061A of the reflective layer 106A. _.5 In _0.5 P is formed from trimethylaluminum (TMA), trimethylgallium (TMG), trimethylindium (TMI), phosphine (PH ₃ ), and dimethylzinc (DMZn) using MOCVD. . Carbon tetrabromide (CBr ₄ ) may be used in place of dimethyl zinc (DMZn).

Each of the surface emitting laser elements 151 to 182 of the surface emitting laser array 200 includes a resonator (= resonator spacer layers 103A and 105A and an active layer 104) and a part of the reflective layer 106A (low refractive index layer 1061A). Since In is contained, the film thickness of the layer containing In becomes thicker than the surface emitting laser elements 1 to 32. Therefore, etching control is further facilitated as compared with the surface emitting laser array 100. Here, it is assumed that In is included only in the low refractive index layer 1061A closest to the resonator in the reflective layer 106A, but the low refractive index is determined from the side closer to the resonator of the reflective layer 106A located above the resonator. Both the layer and the high refractive index layer may include In and may be configured to include a plurality of layers In. In that case, (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P is used as the low refractive index layer, and (Al _0.1 Ga _0.9 ) _0.5 In ₀ is used as the high refractive index layer. _.5 P. And by having a layer containing a plurality of layers In, the total thickness of the layers containing In can be further increased.

In addition, p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P, which is a wide band gap, is often used by doping Zn or Mg, but these dopants are easily diffused. When diffused into the active layer 104, the active layer 104 is damaged, resulting in a decrease in luminous efficiency and a decrease in reliability.

In the surface emitting laser elements 151 to 182, p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P is disposed in the reflective layer 106 A farther from the active layer 104 than the resonator spacer layer 105 A. Since the resonator spacer layers 103A and 105A are made of undoped (Al _0.1 Ga _0.9 ) _0.5 In _0.5 P, adverse effects of impurities can be suppressed.

  Thus, also in the surface emitting laser array 200, the mesa etching for forming the mesa structure is stopped in the middle of the region containing In (= in the middle of the resonator spacer layer 103A), so the mesa interval is small. Even so, the difference Δd between the etching depth in the element gap and the etching depth in the flat portion becomes small, and the low refractive index layer 1021 (= AlAs) of the reflective layer 102 is not exposed in the flat portion. As a result, even if the selective oxidation layer 107 is selectively oxidized, the low refractive index layer 1021 (= AlAs) of the reflective layer 102 is not oxidized.

  Therefore, according to the present invention, heat generated in the active layer 104 can be released to the substrate 1 through the AlAs (low refractive index layer) of the reflective layer 102, and heat can be transferred to the active layer 104 without using a dummy element. It can be hard to hang up.

  Further, the surface emitting laser array 200 includes the surface emitting laser elements 151 to 182 in which the thickness of the layer containing In is thicker than that of the surface emitting laser elements 1 to 32, so that the etching bottom surface has better controllability than the surface emitting laser array 100. Can be stopped in a layer containing In.

  Next, output characteristics of the surface emitting laser array 200 according to the second embodiment will be described. FIG. 17 is a cross-sectional view of the surface emitting laser element according to the second embodiment used in the experiment. FIG. 18 is a cross-sectional view of a comparative surface emitting laser element used in the experiment.

  The sectional view shown in FIG. 17 is obtained by setting the film thickness of the low refractive index layer 1021 (= AlAs) for three periods close to the active layer 104 in the reflective layer 102 of the surface emitting laser element 151 to 3λ / 4. Others are the same as the surface emitting laser element 151.

Further, the cross-sectional view shown in FIG. 18 shows that the reflective layer 102 of the surface emitting laser element 151 is formed by [n-Al _0.3 Ga _0.7 As / n-AlAs] with 30.5 periods and [n- with 10 periods. Al _0.3 Ga _0.7 As / n-Al _0.9 Ga _0.1 As]. Each of n-Al _0.3 Ga _0.7 As, n-AlAs, and n-Al _0.9 Ga _0.1 As has a film thickness of λ / 4.

FIG. 19 is a relationship diagram between the light output and current showing the experimental results. In FIG. 19, the vertical axis represents the optical output, and the horizontal axis represents the current. A curve k9 shows the relationship between the light output and current of the surface emitting laser element according to the present invention, and the curve k10 shows the relationship between the light output and current of the comparative surface emitting laser element. The experiment was performed by observing continuous light (CW) at 20 ° C. using a surface emitting laser element having an area of a light emitting portion of 16 μm ² .

  As is apparent from the experimental results shown in FIG. 19, the saturation value of the light output of the surface emitting laser element according to the present invention is shifted to a higher current value side than the saturation value of the light output of the surface emitting laser element for comparison. Output is obtained. This is because in the surface-emitting laser device according to the present invention, the low refractive index layer 1021 of the reflective layer 102 on the substrate 101 side is all made of AlAs having a high thermal conductivity. This is because the temperature was improved and the temperature rise of the element during element operation was suppressed.

  Thus, by adopting a configuration in which the low refractive index layer 1021 of the reflective layer 102 provided on the substrate 101 is made of AlAs having a high thermal conductivity and the heat generated in the active layer 104 is dissipated to the substrate 101, It has been experimentally proved that the output characteristics of the surface emitting laser element, that is, the output characteristics of the surface emitting laser array can be improved.

  The surface emitting laser array according to the second embodiment may include 40 surface emitting laser elements arranged in 4 rows × 10 columns as in the surface emitting laser array 100A (see FIG. 13). .

The surface-emitting laser array according to the present invention includes surface-emitting laser elements in which the cavity spacer layers 103 and 103A of the surface-emitting laser elements 1 to 40 and 151 to 182 are made of Ga _0.5 In _0.5 P. May be.

Further, in the surface emitting laser array according to the present invention, the cavity spacer layers 103 and 103A of the surface emitting laser elements 1 to 40 and 151 to 182 are made (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P /. A surface emitting laser element composed of Ga _0.5 In _0.5 P may be provided. In this case, (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P is disposed on the active layer 104 side, and Ga _0.5 In _0.5 P is disposed on the reflective layer 102 side. . Thereby, confinement of carriers in the active layer 104 by (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P is improved, and heat generated in the active layer 104 is further dissipated to the reflective layer 102. be able to. This is because Ga _0.5 In _0.5 P has higher thermal conductivity than (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P.

  Table 1 shows that the resonator spacer layers 103 and 105; 103A and 105A / the well layer 1041 of the active layer 104 are formed of AlGaAs / AlGaAs and the resonator spacer layer 103 when formed of AlGaInP / GaInPAs, respectively. 105; 103A and 105A, and the difference in band gap between the well layer 1041 and the difference in band gap between the barrier layer 1042 and the well layer 1041.

  When AlGaAs and AlGaAs are used for the cavity spacer layers 103 and 105; 103A and 105A and the well layer 1041 of the active layer 104, respectively, the cavity spacer layers 103 and 105; 103A and 103A in the surface emitting laser element having an oscillation wavelength of 780 nm are used. The difference in band gap between 105A and the well layer 1041 is 465.9 meV, and the difference in band gap between the barrier layer 1042 and the well layer 1041 is 228.8 meV.

  Further, when AlGaAs and AlGaAs are used for the cavity spacer layers 103 and 105; 103A and 105A and the well layer 1041 of the active layer 104, respectively, the cavity spacer layers 103 and 105 in the surface emitting laser element having an oscillation wavelength of 850 nm; The difference in the band gap between 103A, 105A and the well layer 1041 is 602.6 meV, and the difference in the band gap between the barrier layer 1042 and the well layer 1041 is 365.5 meV.

  On the other hand, when AlGaInP and GaInPAs are used for the cavity spacer layers 103 and 105; 103A and 105A and the well layer 1041 of the active layer 104, the resonances in the surface emitting laser elements 1 to 40 and 151 to 182 having an oscillation wavelength of 780 nm are used. The difference in band gap between the spacer layers 103 and 105; 103A and 105A and the well layer 1041 is 767.3 meV, and the difference in band gap between the barrier layer 1042 and the well layer 1041 is 463.3 meV.

  In this way, the cavity spacer layers 103 and 105; 103A and 105A and the well layer 1041 of the active layer 104 are formed of AlGaInP and GaInPAs, respectively, so that the resonator spacer layers 103 and 105; 103A and 105A and the well layer 1041 The difference in the band gap and the difference in the band gap between the barrier layer 1042 and the well layer 1041 can be significantly increased as compared with the conventional case. As a result, the effect of confining carriers in the well layer 1041 is significantly increased, and the surface emitting laser elements 1 to 40 and 151 to 182 oscillate at a low threshold and radiate higher-power oscillation light.

  Further, since the active layer 104 contains GaInPAs having compressive strain, the increase in gain is increased by band separation between heavy holes and light holes. As a result, high gain and high output oscillation light with a low threshold can be obtained. This effect cannot be obtained with a 780 nm or 850 nm surface emitting laser element made of an AlGaAs system having substantially the same lattice constant as the GaAs substrate.

  Furthermore, the improvement of carrier confinement and the increase in gain due to the active layer 104 having a strained quantum well structure reduce the threshold currents of the surface emitting laser elements 1 to 40 and 151 to 182, and the reflection layer 106 on the light extraction side. , 106A, the reflectance can be reduced, and the output can be further increased.

  Furthermore, since the active layer 104 is made of a material that does not contain Al and is an Al-free active region (a quantum well active layer and a layer adjacent thereto), oxygen incorporation into these regions is reduced. Therefore, the formation of non-radiative recombination centers can be suppressed and the life can be extended. As a result, the writing unit or the light source unit can be reused.

Further, in the above description, it has been described that the low refractive index layer 1021 of the reflective layer 102 is made of AlAs. However, in the present invention, the low refractive index layer 1021 of the reflective layer 102 disposed closer to the substrate 101 than the active layer 104 is. May be made of a semiconductor material having an oxidation rate equal to or higher than the oxidation rate of the selective oxidation layer 107. Since the selective oxidation layer 107 is generally made of Al _x Ga _1-x As (x ≧ 0.9), the low refractive index layer 1021 made of AlAs is generally oxidized of the selective oxidation layer 107. This is because the oxidation rate is equal to or higher than the rate. In the layer containing Al, when the Al composition is different, the higher the Al composition, the faster the oxidation rate. When the Al composition is the same, the higher the layer thickness, the faster the oxidation rate.

Furthermore, in the above description, it has been described that the plurality of low refractive index layers 1021 of the reflective layer 102 are all made of AlAs. The low refractive index layer (= Al _x Ga _1-x As (x ≧ 0.9)) having the oxidation rate of at least the active layer 104 may be provided. Increasing the thermal conductivity of the portion close to the heat source (= active layer 104) is because the effect of radiating the heat generated in the active layer 104 to the substrate 101 is high.

  Further, in the above description, the mesa etching is stopped in the resonator spacer layers 103 and 103A. However, in the present invention, the mesa etching is not limited to this, and the mesa etching is not performed in the surface emitting laser arrays 100 and 100A. In the surface emitting laser array 200, the resonator (resonance) may be stopped in the resonator (resonator spacer layer 103, active layer 104 and resonator spacer layer 105) or at the interface between the resonator and the reflection layer 106. The spacer layer 103A, the active layer 104 and the resonator spacer layer 105A) or in the low refractive index layer 1061A of the reflective layer 106A or at the interface between the low refractive index layer 1061A and the high refractive index layer 1062, Specifically, it may be stopped on the reflective layer 106 side with respect to the reflective layer 102.

[Embodiment 3]
FIG. 20 is a plan view of the surface emitting laser array according to the third embodiment. Referring to FIG. 20, the surface emitting laser array 300 according to the third embodiment includes a substrate 310, surface emitting laser elements 311 to 320, and pads 321 to 330.

  The surface emitting laser elements 311 to 320 are arranged one-dimensionally on the substrate 310. Each of the surface emitting laser elements 311 to 320 includes the surface emitting laser elements 1 to 40 or the surface emitting laser elements 151 to 182 described above.

  The pads 321 to 330 are respectively arranged around the surface emitting laser elements 311 to 320 and connected to the p-side electrode 111.

  By integrating a large number of surface-emitting laser elements 311 to 320 that can suppress a threshold rise and can operate at high power on the same substrate 310, for example, when used for optical communication, data transmission by multiple beams can be performed simultaneously. Therefore, high-speed communication can be performed. In addition, the surface emitting laser elements 311 to 320 operate with low power consumption and have good heat dissipation characteristics of the heat generated in the active layer 104. Therefore, particularly when the surface emitting laser elements 311 to 320 are used by being incorporated in a device, the temperature rise is reduced. be able to.

[Embodiment 4]
A method of manufacturing the surface emitting laser array according to the fourth embodiment is shown in FIGS.

(1) On the substrate 101, the reflective layer (lower reflective mirror) 102, the resonator spacer layer (lower spacer layer) 103, and the active material are formed on the substrate 101 by crystal growth using metal organic chemical vapor deposition (MOCVD). A semiconductor layer such as a layer 104, the resonator spacer layer (upper spacer layer) 105, the selective oxide layer 107, and the reflective layer (upper reflecting mirror) 106 is sequentially stacked (see FIG. 21A). Hereinafter, a structure in which these semiconductor layers are stacked is also referred to as a “semiconductor stacked body”.

(2) A photomask PM is patterned on the surface of the stacked body, which is the surface (surface opposite to the substrate 101) in the semiconductor stacked body, corresponding to the light emitting portion and the array boundary portion by photolithography (FIG. 21B). reference). Here, as an example, one chip has nine (3 × 3) light emitting units.

(3) A mesa shape is formed by dry etching using the photomask PM as an etching mask (see FIG. 21C). In the following, for convenience, the mesa-shaped portion is abbreviated as “mesa”. At this time, the portion that becomes the array boundary is also etched at the same time. Here, the etching is performed until the bottom surface of the etching reaches the lower spacer layer 103.

(4) The photomask PM is removed.

(5) A current confinement structure is formed in the selective oxidation layer 107 (see FIG. 21D).

(6) An etching mask for etching the array boundary is patterned by photolithography.

(7) The array boundary is etched until the bottom surface of the etching reaches the substrate 101 (see FIG. 22A). As a result, each array part is separated from the other array part and is formed into a so-called island.

(8) As a passivation film, a protective film 109 made of any one of SiO ₂ , SiN, and SiON is formed (see FIG. 22B).

(9) Etch away the contact on the top of the mesa and the passivation film at the bottom of the array boundary (see FIG. 22C). At this time, the passivation film on the side surface of the array boundary is masked so as not to be etched.

(10) The p-side electrode 111 is formed by a lift-off method (see FIG. 22D). Specifically, portions other than the electrode are masked in advance with a photoresist, and after the electrode material is deposited, ultrasonic cleaning is performed in a solution in which the photoresist such as acetone is dissolved. As the electrode material on the p side, a multilayer film made of Cr / AuZn / Au or a multilayer film made of Ti / Pt / Au is used.

(11) After polishing the back side of the substrate 101 to a predetermined thickness (for example, about 100 μm), the n-side electrode 112 is formed (see FIG. 23). Here, the n-side electrode 112 is a multilayer film made of AuGe / Ni / Au.

(12) A plurality of electrode pads (not shown) and wirings for electrically connecting the p-side electrode 111 of each light emitting unit and the corresponding electrode pads are formed. The p-side electrode 111 has a window at its center, and laser light is emitted from this portion. Thereby, each mesa becomes a light emission part, respectively.

(13) Cut along the divided portion on the bottom surface of the array boundary and divide into chips.

  A surface-emitting laser array 350 according to the fourth embodiment manufactured as described above is shown in FIG.

  Since this surface emitting laser array 350 is formed into an island at the time of manufacture, warpage of the substrate 101 can be reduced. Therefore, the manufacturing yield can be improved and the cost can be reduced.

  In the surface emitting laser array 350, since the side surface of the lower reflecting mirror 102 is covered with a protective film, the low refractive index layer of the lower reflecting mirror 102 is oxidized by reacting with moisture in the atmosphere, and distortion occurs. It is possible to suppress the progress of destruction. That is, deterioration over time can be prevented, and a highly reliable surface emitting laser array can be realized.

[Application example]
FIG. 25 is a schematic diagram showing a configuration of an optical scanning device using the surface emitting laser array 100A shown in FIG. Referring to FIG. 25, an optical scanning device 400 includes a light source 401, a coupling lens 402, an aperture 403, an anamorphic lens 404, a polygon mirror 405, a deflector-side scanning lens 406, and an image plane side. A scanning lens 407, a dustproof glass 408, an image surface glass 408, an image surface 409, a soundproof glass 410, and a dummy lens 411 are provided.

  The light source 401 includes the surface emitting laser array 100A shown in FIG. The 40 luminous fluxes emitted from the light source 401 are incident on the coupling lens 402, are made weak divergent light by the coupling lens 402, and are incident on the anamorphic lens 404.

  The light beam incident on the anamorphic lens 404 is changed by the anamorphic lens 404 so that the main scanning direction is made parallel light and the sub-scanning direction is converged near the polygon mirror 405. Thereafter, the light beam enters the polygon mirror 405 through the aperture 403, the dummy lens 411, and the soundproof glass 410.

  The light beam is deflected by the polygon mirror 405, and forms an image on the image plane 409 through the dust-proof glass 408 by the deflector-side scanning lens 406 and the image plane-side scanning lens 407.

  The light source 401 and the coupling lens 402 are fixed to the same member made of aluminum.

  The light source 401 is a sub-scan of 10 perpendicular lines drawn down from 10 centers of 10 surface emitting laser elements 1 to 10/11 to 20/21 to 30/31 to 40 in a straight line arranged in the sub-scanning direction. Since the surface-emitting laser array 100A includes 40 surface-emitting laser elements 1 to 40 arranged so that the intervals in the direction are equal to c2, the lighting timing of the 40 surface-emitting laser elements 1 to 40 is determined. By adjusting, it can be grasped as the same configuration as the case where the light sources are arranged at equal intervals in the sub-scanning direction on the photosensitive member.

  Further, by adjusting the element interval c2 of the surface emitting laser elements 1 to 40 and the magnification of the optical system, the interval written in the sub-scanning direction can be adjusted. That is, when the surface emitting laser array 100A (40 channels) is used as the light source 401, the element interval c2 is set to 2.4 μm as described above, so the magnification of the optical system is set to about 2.2 times. Accordingly, high-density writing of 4800 dpi (dot / inch) can be performed. Further, the distance c2 can be further reduced by increasing the number of elements in the main scanning direction, the distance d between adjacent surface emitting laser elements in the sub-scanning direction being further narrowed, or the magnification of the optical system can be reduced. Thus, higher density writing is possible, and higher quality printing is possible. In this case, the writing interval in the main scanning direction can be easily controlled by adjusting the lighting timing of the light source 401.

  As described above, in the optical scanning device 400, 40 dots can be simultaneously written, and high-speed printing can be performed. Higher-speed printing is possible by increasing the number of surface emitting laser elements in the surface emitting laser array 100A.

  Further, by using the surface emitting laser elements 1 to 40 and 151 to 182 for the surface emitting laser array 100A, the life of the surface emitting laser array 100A is remarkably improved, so that the writing unit or the light source unit can be reused. .

  In the optical scanning device 400, the light source 401 may be constituted by the surface emitting laser array 100 shown in FIG. 1 or the surface emitting laser array 200 shown in FIG.

  FIG. 26 is a schematic diagram of a laser printer. Referring to FIG. 26, the laser printer 500 includes a photosensitive drum 501, an optical scanning device 502, a cleaning unit 503, a charging unit 504, a developing unit 505, a transfer unit 506, and a fixing unit 507. .

  The optical scanning device 502, the cleaning unit 503, the charging unit 504, the developing unit 505, the transfer unit 506, and the fixing unit 507 are disposed around the photosensitive drum 501.

  The optical scanning device 502 includes the optical scanning device 400 shown in FIG. 25, and forms a latent image on the photosensitive drum 501 using a plurality of laser beams by the method described above. The cleaning unit 503 removes toner remaining on the photosensitive drum 501.

  The charging unit 504 charges the surface of the photosensitive drum 501. The developing unit 505 guides toner to the surface of the photosensitive drum 501 and performs toner development on the latent image formed by the optical scanning device 502.

  The transfer unit 506 transfers the toner image. The fixing unit 507 fixes the transferred toner image.

  When a series of operations is started in the laser printer 500, the charging unit 504 charges the surface of the photosensitive drum 501 and the optical scanning device 502 forms a latent image on the photosensitive drum 501 by a plurality of laser beams. To do. The developing unit 505 performs toner development on the latent image formed by the optical scanning device 502, the transfer unit 506 transfers the toner image, and the fixing unit 507 fixes the transferred toner image. As a result, the toner image is transferred onto the recording paper 508, and then the toner image is heat-fixed by the fixing unit 507 to complete the formation of the electrophotographic image.

  On the other hand, the static elimination unit (not shown) erases the latent image on the photosensitive drum 501, and the cleaning unit 503 removes the toner remaining on the photosensitive drum 501. Thereby, a series of operations are completed, and by repeating the above-described operations, it is possible to output electrophotographic images continuously and at high speed.

  The laser printer 500 constitutes an “image forming apparatus”.

  FIG. 27 is a schematic diagram of an image forming apparatus. Referring to FIG. 27, image forming apparatus 600 includes photoreceptors 1Y, 1M, 1C, and 1K, chargers 2Y, 2M, 2C, and 2K, developing devices 4Y, 4M, 4C, and 4K, and cleaning units 5Y and 5Y. 5M, 5C, 5K, transfer charging means 6Y, 6M, 6C, 6K, fixing means 610, writing unit 620, and transfer belt 630. Y represents yellow, M represents magenta, C represents cyan, and K represents black.

  The photoreceptors 1Y, 1M, 1C, and 1K rotate in the direction of the arrows, and in the order of rotation, the chargers 2Y, 2M, 2C, and 2K, the developing devices 4Y, 4M, 4C, and 4K, and the transfer charging units 6Y, 6M, and 6C. , 6K and cleaning means 5Y, 5M, 5C, 5K are arranged.

  The chargers 2Y, 2M, 2C, and 2K are charging members that constitute a charging device for uniformly charging the surfaces of the photoreceptors 1Y, 1M, 1C, and 1K. A writing unit 620 (= consisting of an optical scanning device 400) is provided on the surface of the photoreceptors 1Y, 1M, 1C, 1K between the chargers 2Y, 2M, 2C, 2K and the developing devices 4Y, 4M, 4C, 4K. Beams are irradiated, and electrostatic images are formed on the photoreceptors 1Y, 1M, 1C, and 1K. The developing units 4Y, 4M, 4C, and 4K form toner images on the surfaces of the photoreceptors 1Y, 1M, 1C, and 1K based on the electrostatic images. The transfer charging units 6Y, 6M, 6C, and 6K sequentially transfer the transfer toner images of the respective colors onto the recording paper 640, and the fixing unit 610 finally fixes the image onto the recording paper 640.

  Although color misregistration of each color may occur due to mechanical accuracy or the like, the image forming apparatus 600 is compatible with high density, and the order in which a plurality of surface emitting laser elements of the surface emitting laser array used in the writing unit 620 is lit is set. By changing it, it is possible to improve the accuracy of correcting the color misregistration of each color.

  FIG. 28 is a schematic diagram of an optical transmission module. Referring to FIG. 28, the optical transmission module 700 includes a surface emitting laser array 701 and an optical fiber 702. The surface emitting laser array 701 has a structure in which a plurality of surface emitting laser elements 1 to 40 and 151 to 182 are arranged one-dimensionally. The optical fiber 702 is composed of a plurality of plastic optical fibers (POF). The plurality of plastic optical fibers are arranged corresponding to the plurality of surface emitting laser elements 1 to 40 and 151 to 182 of the surface emitting laser array 701.

  In the optical transmission module 700, the laser light emitted from the surface emitting laser elements 1 to 40 and 151 to 182 is transmitted to the corresponding plastic optical fiber. An acrylic plastic optical fiber has a bottom of absorption loss at 650 nm and a surface-emitting laser element having a wavelength of 650 nm has been studied. However, the high-temperature characteristic is poor and has not been put into practical use.

  Although an LED (Light Emitting Diode) is used as a light source, high-speed modulation is difficult, and a semiconductor laser is required to realize high-speed transmission exceeding 1 Gbps.

  The oscillation wavelengths of the surface emitting laser elements 1 to 40 and 151 to 182 described above are 780 nm, but the heat dissipation characteristics are improved, the output is high, the temperature characteristics are excellent, and the absorption loss of the optical fiber increases. However, if it is a short distance, transmission is possible.

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

  In the optical transmission module 700, the surface emitting laser elements 1 to 40, 151 to 182 and the optical fiber are made to correspond one-to-one, but a plurality of surface emitting laser elements having different oscillation wavelengths are arrayed in one or two dimensions. It is possible to further increase the transmission rate by arranging in the wavelength division multiplexing and wavelength multiplexing transmission.

  Further, when an optical transmission module 700 in which surface emitting laser arrays using surface emitting laser elements 1 to 40 and 151 to 182 are combined with an inexpensive POF is used in an optical communication system, a low cost optical transmission module can be realized. In addition, a low-cost optical communication system using this can be realized. Since the cost is extremely low, it is effective for short-distance data communication for home use, office room use, and in an apparatus.

  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 array in which heat is not easily trapped in an active layer without using a dummy element. In addition, the present invention is applied to an optical scanning device including a surface emitting laser array that does not easily trap heat in an active layer without using a dummy element. Furthermore, the present invention is applied to an image forming apparatus provided with a surface emitting laser array in which heat is not easily trapped in an active layer without using a dummy element.

1 to 40, 151 to 182, 311 to 320 ... surface emitting laser elements, 51 to 90, 321 to 330 ... pads, 100, 100A, 200, 300, 701 ... surface emitting laser arrays, 101 ... substrate, 102, 106, 106A ... reflective layer, 103, 103A, 105, 105A ... resonator spacer layer, 104 ... active layer, 107 ... selective oxide layer, 107a ... non-oxidized region, 107b ... oxidized region, 108 ... contact layer, 109 ... SiO ₂ layer , 110 ... insulating resin, 111 ... p-side electrode, 112 ... n-side electrode, 120 ... resist pattern, 131 to 134 ... mesa structure, 141 to 145 ... skirting, 350 ... surface emitting laser array, 400, 502 ... Optical scanning device 401 ... Light source 402 ... Coupling lens 403 ... Aperture 404 ... Anamorphic lens 405 ... polygon mirror, 406 ... deflector side scanning lens, 407 ... image side scanning lens, 408 ... dust-proof glass, 409 ... image surface, 410 ... soundproof glass, 411 ... dummy lens, 500 ... laser printer, 501 ... photosensitive Body drum, 503... Cleaning unit, 504 .. charging unit, 505... Development unit, 506 .. transfer unit, 507 .. fixing unit, 600... Image forming apparatus, 1Y, 1M, 1C, 1K .. photoconductor, 2Y, 2M, 2C , 2K ... charger, 4Y, 4M, 4C, 4K ... developer, 5Y, 5M, 5C, 5K ... cleaning means, 6Y, 6M, 6C, 6K ... transfer charging means, 610 ... fixing means, 620 ... writing unit 630 ... transfer belt, 640 ... recording paper, 700 ... light transmission module, 702 ... optical fiber, 1021,106 ... low-refractive index layer, 1022,1062 ... high refractive index layer, 1023,1063 ... composition gradient layer, 1041 ... well layers, 1042 ... barrier layer, W1～W40 ... wire.

JP 2002-164621 A Japanese Patent Laid-Open No. 9-18093 JP 2000-114656 A

2004 IEICE Electronics Society Conference, CS-3-4 IEEE PHOTOTONICS TECHNOLOGY LETTERS, VOL. 11, no. 12, 1999, pp 1539-1541.

Claims (10)

An element arrangement portion on which a plurality of surface-emitting laser elements including a mesa structure formed by etching is provided; and an element arrangement portion provided on the substrate and in an in-plane direction of the substrate. A surface emitting laser array comprising a flat portion provided around,
Each of the plurality of surface emitting laser elements includes:
A first reflective layer comprising a semiconductor Bragg reflector, formed on the substrate;
A resonator formed of a plurality of layers each formed of an AlGaInPAs-based material containing at least In and formed on the first reflective layer;
A second reflective layer comprising the semiconductor Bragg reflector, formed on the resonator and including a selective oxidation layer having a current confinement structure;
The first reflective layer includes a low refractive index layer made of AlAs having an oxidation rate equal to or higher than that of the selective oxidation layer on at least the resonator side,
The second reflective layer includes a layer made of an AlGaAs-based material,
The etching rate of the resonator is slower than the etching rate of the layer made of the AlGaAs material in the second reflective layer,
The etching bottom surface of the gap portion of the plurality of surface emitting laser elements and the etching bottom surface of the flat portion in the element arrangement portion are both in a layer made of an AlGaInPAs-based material containing at least In of the resonator in the thickness direction. Located
The surface emitting laser array in which the bottom surface of the gap portion of the plurality of surface emitting laser elements in the element arrangement portion is located farther from the substrate than the bottom surface of the flat portion.   2. The difference between the etching depth in the gap and the etching depth in the flat portion is equal to or less than half of the oscillation wavelength of the surface-emitting laser element as an effective length in the medium. Surface emitting laser array.   The distance between two adjacent surface-emitting laser elements in the gap portion is the distance between the two mesa structures at the top surface position of the mesa structure and the distance between the two mesa structures at the bottom surface position of the mesa structure. The surface-emitting laser array according to claim 1, wherein the surface-emitting laser array has a narrower spacing of 20 μm or less.   4. The surface emitting laser array according to claim 1, wherein a side surface of the first reflective layer is covered with a protective film. 5. The surface emitting laser array according to claim 4, wherein the protective film is one of SiO ₂ , SiN, and SiON.   The aluminum composition of the low refractive index layer arrange | positioned at the said resonator side of the said 1st reflection layer is larger than the aluminum composition of the said selective oxidation layer, It is any one of Claims 1-5. Surface emitting laser array. The aluminum composition of the low refractive index layer disposed on the resonator side of the first reflective layer is the same as the aluminum composition of the selective oxidation layer,
The film thickness of the low-refractive-index layer arrange | positioned at the said resonator side of the said 1st reflection layer is thicker than the film thickness of the said selective oxidation layer of any one of Claims 1-5. Surface emitting laser array. The surface emitting laser array according to any one of claims 1 to 7,
Deflecting means for deflecting a plurality of beams emitted from the surface emitting laser array;
An optical scanning device comprising: a scanning optical element that guides a beam from the deflecting unit onto a surface to be scanned.   An image forming apparatus comprising the optical scanning device according to claim 8. An image forming apparatus comprising the surface emitting laser array according to any one of claims 1 to 7 as a writing light source.