JP2002198613A - Semiconductor device having salient structure, and method of manufacturing the semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the heat characteristics of a semiconductor device having a salient structure. SOLUTION: The semiconductor device has the salient structure 108 that has been machined saliently. An irregular structure 109 for cooling is formed at one or the entire portion of the sidewall of the salient structure 108.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser such as a surface emitting laser and a semiconductor device such as an optical integrated device, and more particularly to a semiconductor device having a structure processed into a projection shape and a method of manufacturing the same.

[0002]

2. Description of the Related Art For the application of large-capacity parallel optical information processing, high-speed optical connection, thin display elements, optical recording devices, and the like, development of a two-dimensional array type surface solid-state light emitting element is desired. For these applications, low cost, low power consumption, high productivity,
High reliability is a necessary condition. Various materials have been researched and developed.Semiconductor single crystals are very suitable to ensure the reliability of devices.In particular, the development of surface light-emitting devices using compound semiconductors has been actively pursued. Have been done. In a compound semiconductor, light can be used in a wide wavelength range from ultraviolet to infrared by changing the substrate and the material, and is promising as a display element. Also, among the light-emitting elements, the laser diode (LD) having reflection mirrors at both end surfaces has extremely high luminous efficiency compared to natural light emission, and can reduce power consumption even when it is formed in a two-dimensional array. . From such a viewpoint, a vertical type semiconductor laser (Vertical Cavity Surface Emitting Laser: VC
SEL) has been actively developed in recent years.

[0003] Currently, VCSELs are also being developed from a blue wavelength of about 400 nm to a communication wavelength band of 1.55 μm, and AlGaN / InGaN on a sapphire substrate, and InGaAlP / I on a GaAs substrate.
nAlP, InGaAs / AlGaAs, InGaAs / InGaAsP on InP substrate
It is being studied in material systems such as systems.

By the way, in order to electrically insulate one active region in a semiconductor device, ions are implanted around the active region to make it insulated, or a mesa structure is formed around the active region to spatially isolate the active region. Separation is performed. For example, I
EEE, Journal of Quantum Electronics, Vol. 27, No. 6, pp. 1332-1346 (1991) (IEEE
Journal of Quantum Electronics, vol. 27, No.
6, pp. 1332-1346 (1991)).

FIG. 13 is a sectional view of this surface emitting laser.
This surface-emitting laser has an n-GaAs substrate 101, an n-type Bragg reflector 102, an active layer 104, a p-type Bragg reflector 106, an upper electrode
After the layers 110 are stacked in this order, the p-type Bragg reflector 106 and the active layer 104 are etched, and the resonator is processed into a protruding shape (the protruding resonator is also called an air post).
The laser light is emitted from the back surface of the substrate 101.

In a surface emitting semiconductor laser having a vertical cavity structure having such a structure, a mirror having an extremely high reflectivity is formed by using a multilayer reflective film so that the light confinement coefficient can be increased, and the cavity length can be increased. Can be equivalent to As a result, an extremely low threshold value and a reduction in light lifetime can be achieved. In addition, a multilayer reflector (hereinafter referred to as DBR reflector)
(Also called Distributed Bragg Reflection Mirror)
Is used, the light emission condition is limited to light that satisfies the Bragg reflection condition, oscillation light of a predetermined wavelength is obtained only in a direction perpendicular to the multilayer reflection film, and a single-mode semiconductor laser is used. It can also be configured.

In this type of vertical cavity surface emitting semiconductor laser, power is supplied through the DBR reflector, and light is led out through one of them. For this reason, the multilayer reflective film is formed by a
An R reflector is used, and this DBR reflector has a problem of an increase in series resistance particularly in a p-side DBR having low carrier mobility.

That is, since the mobility of the hole is 1/10 or less of that of the electron, the DBR reflecting mirror on the p side,
In the above example, the series resistance on the p-type Bragg reflector 106 side becomes a problem, and this results in an increase in thermal resistance.

This resistance can be reduced to some extent by high-concentration doping. In this case, light absorption by free carriers (plasmon absorption) is an obstacle to efficient oscillation. For this reason, impurity doping of usually 5 × 10 ¹⁸ cm ⁻³ or more is to be avoided, and therefore, it is not possible to sufficiently reduce the on-resistance on the p-side. Therefore, there has been a problem that thermal resistance increases at the time of high current injection, and it is difficult to increase the output.

As described above, the main factor that generally limits the output of a semiconductor laser or impairs its reliability is an increase in temperature due to heat generation during element driving. As one method of suppressing a temperature rise, a method of increasing heat dissipation is generally used. A semiconductor laser device is formed on a compound semiconductor substrate. However, heat dissipation to the substrate side cannot be expected much because the compound semiconductor has low thermal conductivity. Therefore, in the case of the edge-emitting type semiconductor laser, a method of increasing the heat radiation by directly contacting the element forming portion with the heat sink is a common means.

However, in the case of a surface emitting type semiconductor laser of the surface emitting type, since the laser may be emitted to the surface of the substrate on which the element is formed, a heat sink cannot be brought into direct contact with the element and heat radiation is difficult. There was a problem that there is.

To solve such a problem, the following solutions have been proposed. For example, a surface emitting laser having a structure in which an electrode having a heat sink effect is attached to a side surface of at least one multilayer film reflecting mirror is disclosed (Japanese Patent Application Laid-Open No. 05-283796). The structure is shown in FIG. In a surface emitting semiconductor laser having a vertical cavity structure having multilayer film reflecting mirrors (DBR reflecting mirrors) 102 and 106, at least one of the electrodes 118 is disposed on the corresponding side of the DBR reflecting mirror 106 with respect to the DBR reflecting mirror 106. By using an electrode having a heat sink function that comes into contact along the multilayer film laminated side surface, thermal resistance, which is a problem in the semiconductor multilayer film reflecting mirror, can be reduced, and a large output can be achieved.

The main heat sources in a surface emitting semiconductor laser having an air post structure are an active layer 104 and a p-type semiconductor multilayer reflective layer 105.
Or the Joule heat due to the contact resistance between the p-type contact layer and the upper electrode. These heat sources mainly exist in the resonator projection and its vicinity. For this reason, by embedding the periphery of the resonator protrusions in close contact with a metal having excellent heat conduction, the heat radiation can be increased and the element temperature can be greatly reduced.

Further, when a single active region is made highly efficient and miniaturized, it becomes difficult to electrically or optically separate elements, and at the same time, it is necessary to increase the heat radiation efficiency.
Although a method based on ion implantation has been proposed, this method causes a large damage to the crystal, and it is difficult to use the method particularly in a high-height element. For this reason, a mesa structure is formed and embedded with a material that can be electrically and optically narrowed. For this purpose, it is desirable to use a material having a large thermal difference between the active region and the buried region of the element, such as a difference in refractive index , and a high buried material.

Based on such an object, for example,
In 9-45985, a semiconductor laser using a layer mainly composed of AlN having excellent thermal conductivity as a buried layer is manufactured. However, AlN is harder than other semiconductors and has a different coefficient of thermal expansion from other semiconductors. Therefore, when this kind of material is used, dislocations and strains are likely to be introduced to other semiconductors forming the active region. In particular, when heated to a high temperature in the manufacturing process, an abnormal layer is generated at the buried interface, and there is a concern that a high quality active layer cannot be obtained. For this reason, a structure in which the periphery of the air post is embedded with AlGaN (JP-A-11-274645) is also disclosed.

[0016] For the same purpose, a resonator having at least a part in a protruding shape and an opening formed on the upper surface of the resonator are formed continuously along the surface of the resonator and an insulating film formed around the resonator. Also disclosed is a structure characterized by comprising a buried layer made of a metal having a melting point of 400 ° C. or less formed so as to be in close contact with the upper electrode and the upper electrode (JP-A-11-261153). .

By the way, the VCSEL is also required to have a lower threshold, but the following structure has been proposed as an approach. It is selective etching of AlAs layer near active layer (OSA, SEMICONDUCTOR, LASERS'95, Technica
l Digest, p. 106 (1995)) to form a current constriction structure. In addition, a structure has been proposed in which AlAs constituting a DBR mirror is selectively oxidized (ELECTRONICS LETTERS, 31, p.560 (1995)) to form a current confinement structure. In the example of such a current confinement structure, a threshold value of 100 μA or less has been achieved.

[0018]

However, as described above, the heat dissipation can be improved by embedding the protruding resonator formed by etching with AlN or AlGaN, which is one digit higher in thermal conductivity than a semiconductor. Although a structure for improving the heat radiation efficiency around the air post is disclosed, it is necessary to further improve the heat radiation efficiency in order to improve the laser characteristics and to provide an integrated semiconductor laser.

The current confinement structure using the Al oxide layer also has a large problem in terms of heat radiation. That is, the thermal resistance of the Al oxide layer is about 5 to 10 times larger than that of the AlAs layer, so that heat dissipation of the resonator projections to the substrate side is hindered, resulting in an increase in driving temperature. The main heat sources in the surface-emitting type semiconductor laser having the projecting resonator structure are considered to be as described above, and these heat sources mainly exist in the resonator protrusions. The current confinement layer must be formed on the resonator projection for convenience in the manufacturing method, and the current confinement layer is formed near the root of the resonator projection because the current confinement effect disappears when it is separated from the active layer. I can't help but. By arranging the current confinement layer having a high thermal resistance at the base of the resonator projection, the resonator projection is easily thermally isolated, and the driving temperature is higher than that of the projection resonator structure having no current confinement layer. Invite a rise. As a result, a desired laser output may not be obtained.
In addition, there was a major problem in that the reliability was particularly reduced due to the influence of heat.

An object of the present invention is to increase the thermal resistance at the time of high current injection due to the increase of the on-resistance in the vertical cavity surface emitting semiconductor laser particularly by the semiconductor multilayer film reflecting mirror, and to inhibit the increase in output as described above. Surface emitting lasers, edge emitting semiconductor lasers, light emitting diodes (LE
D) to solve the problem of thermal characteristics of semiconductor devices such as photodiodes.

[0021]

According to the present invention, there is provided a semiconductor device having a projecting structure processed into a projecting shape, wherein a part or all of a side wall of the projecting structure is provided. An uneven structure for heat radiation is formed. The concavo-convex structure may be any structure as long as it increases the surface area and exhibits a heat radiation effect, and may be any structure, whether periodic or random. Also,
It may have a porous structure or a spongy structure. However,
The structure must not be so rough as to impair the original function of the device.

Further, the type of the semiconductor element is not limited, and any type may be used as long as it has a protruding structure and is desired to improve the heat radiation effect by increasing the surface area of the side wall.

Hereinafter, more specific embodiments will be described. The semiconductor element is typically a semiconductor light emitting element having a projecting resonator structure processed into a projecting shape in which improvement in heat radiation effect is particularly desired, and part or all of the side walls of the projecting resonator structure. The uneven structure for heat dissipation is formed. Examples of the semiconductor light emitting device include the following.

This is a surface emitting laser described in an embodiment described later, which is a p-type distribution having a stacked structure in which an active layer and a pair of layers having different compositions provided so as to sandwich the active layer are repeatedly stacked. A black reflector and an n-type distributed black reflector are provided, and part or all of them have the air post-like projection structure. Layers forming a pair having different compositions may have a uniform composition in each layer (see FIG. 10),
The composition changes continuously in each layer (see FIG. 11). In this case, preferably, the concave-convex structure is formed as a concave-convex structure in which annular concave-convex portions formed by using the stacked structure are overlapped along the side wall of the distributed Bragg reflector in the convex structure.

The semiconductor light emitting device is of a Fabry-Perot type,
The DFB type or DBR type edge emitting semiconductor laser may be used. In this case, the projecting resonator structure is a mesa structure in a stripe shape (in this case, the stripe extending direction is the resonator direction).

The semiconductor element may be a semiconductor light receiving element having a protruding structure. As an example of this, there is a surface emitting laser structure having a structure in which at least one of the distributed black reflectors is removed, and performing light detection by applying a reverse voltage to the active layer.

The uneven structure is formed on the side wall of the protruding structure by anodizing treatment (forming an anodic oxide film which is a porous film in an appropriate electrolyte solution) with an appropriate portion of the element covered with an insulating film. It is formed by forming a rough surface, or is formed by mechanically rubbing the side wall of the protruding structure with an abrasive while the appropriate portion of the device is covered with a protective film, or the appropriate portion of the device is covered with a protective film. In this state, a rough surface may be formed on the side wall of the protruding structure by plasma etching. Since these methods do not form a concavo-convex structure using a laminated structure, they can be applied to semiconductor elements of any structure.

The protruding structure may be buried with a layer mainly composed of Al ₂ O _3, AlN or AlGaN. This can also be applied to a semiconductor element having any structure, thereby further improving the heat radiation effect.

In the surface emitting laser, an insulating film is provided so as to electrically insulate the p-type distributed Bragg reflector and the n-type distributed Bragg reflector provided so as to sandwich the active layer,
An electrode metal film may be provided on the insulating film so as to be in contact with at least a side wall of the air-post distributed Bragg reflector. Thereby, the injection current does not spread and the reactive current can be suppressed.

After the formation of an appropriate insulating layer, the protruding structure may be buried with a metal burying layer. This can also be applied to a semiconductor element having any structure, thereby further improving the heat radiation effect.

The semiconductor device may be configured as a semiconductor light emitting device having an active layer, and may further have a current confinement structure for narrowing a current path to the active layer. Thus, in combination with the improvement of the heat radiation efficiency due to the uneven structure of the side wall of the protruding structure, the threshold value of the element can be reduced, and the characteristics can be improved and stabilized.

In the case of the above-mentioned surface emitting laser, when it further has a current confinement structure for narrowing a current path to the active layer,
It is preferable that an optical path width limited by the current confinement structure is smaller than a distance between concave portions facing each other in an in-plane direction of the concavo-convex structure provided on a side wall of the distributed Bragg reflector.

Further, an optical recording apparatus of the present invention for achieving the above object is characterized in that recording is performed on an optical recording medium using the above-mentioned semiconductor light emitting element as a light source. Preferably, the light source comprises a plurality of surface emitting lasers as described above.

Furthermore, the method for manufacturing a surface emitting laser according to the present invention that achieves the above object has a laminated structure in which an active layer and a pair of layers having different compositions provided so as to sandwich the active layer are repeatedly laminated. A method of manufacturing a surface emitting laser comprising a p-type distributed black reflector and an n-type distributed black reflector, part or all of which has an air post-like projection structure, comprising at least an air post-like distributed Bragg reflector Forming a concave-convex structure for heat dissipation in which annular concave-convex portions are overlapped on the side wall of the substrate using the laminated structure. This makes it possible to easily and reliably form an effective heat-releasing concave / convex structure on the air post using the laminated structure of the surface emitting laser.

Typically, the air-post-like projection structure is formed by dry etching, and the concavo-convex structure is formed by wet etching.

If the Al concentration of the layers forming the pairs having different compositions is made different and the difference in Al concentration is used, an uneven structure can be easily and reliably formed on the side wall of the distributed Bragg reflector.

Further, the Al concentration of the paired layers having different compositions is made different, and an oxidized portion is formed on the side wall of the distributed Bragg reflector by utilizing the difference in Al concentration. The uneven structure can be easily and reliably formed by etching.

At this time, if the composition of each layer of the pair having different composition is uniform, the concavo-convex structure is formed as a concavo-convex structure having a substantially rectangular cross section. Further, if the composition of each of the layers forming the pair having a different composition changes continuously, the concavo-convex structure is formed as a concavo-convex structure whose cross section changes in a substantially sine curve shape. In any case, an effective heat dissipation uneven structure is obtained.

Further, if the heat dissipation is further improved by embedding the periphery of the air-post-shaped distributed Bragg reflector with an insulator or metal, further improvement and stabilization of the luminous efficiency can be achieved.

[0040]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a semiconductor light emitting device such as a surface emitting laser according to the present invention will be described below with reference to the drawings.

(First Embodiment) The first embodiment is a surface emitting laser having an annular concavo-convex structure on the side wall of an air post.
Figure 1 shows this structure.

This surface-emitting type semiconductor laser comprises an n-type semiconductor multilayer reflective layer (n-type distributed layer) on an n-type GaAs substrate 101.
Bragg Reflection Layer (n-DBR) 102, n-type spacer layer 103, active layer 104, p-type spacer layer 105, p-type semiconductor multilayer reflection layer (p-DBR) 106, and p-type contact layer 107. The layers are sequentially epitaxially stacked. Then, the resonator protrusions 108 are etched through the p-type contact layer 107 and the p-DBR 106 so as to project halfway through the p-type spacer layer 105.
(Air post) is formed. Further, on the side wall of the air post, there is formed an uneven structure 109 in which annular unevenness is repeated, and the surface area of the side wall of the resonator is increased in order to improve heat radiation.

An upper electrode 110 is formed on the air post 108, and a lower electrode 111 is connected to the n-GaAs substrate 101. The insulating film 112 on which the upper electrode 110 is formed is exposed p
It is formed on the mold spacer layer 105 and the p-DBR 106 to such an extent that the injection current slightly increases. By forming this air post 108,
The injected current does not spread, the reactive current can be suppressed, and efficient laser oscillation becomes possible. Air post 108
As for the unevenness of the side wall, when the surrounding area is air, a larger unevenness step provides a greater heat dissipation effect. However, in consideration of the actual process and the device characteristics, a step of 100 nm or less is desirable.

Next, a method of manufacturing the surface emitting laser of this embodiment will be described with reference to FIG. n-DBR10 on n-type GaAs substrate 101
2, n-type spacer layer 103, active layer 104, and p-type spacer layer 105
The p-DBR 106 and the p-type contact layer 107 are sequentially epitaxially grown by metal organic chemical vapor deposition or MBE (molecular beam epitaxy) (FIG. 2 (a)). Here, n-DBR102 is AlAs and Al
_0.15 Ga _O.85 As is alternately stacked in 30 pairs, p-DBR106 is AlAs
And Al _0.15 Ga _0.85 As are alternately stacked in 25 pairs. Active layer 104
Are three GaAs well layers and A
The active layer is a multiple quantum well active layer composed of a barrier layer of l _0.3 Ga _0.7 As. The p-type contact layer 107 has a carrier concentration of 1 × 10
^It consists of a GaAs layer of ¹⁹ cm ^-3 or more. Si or the like can be used as the n-type dopant, and C or the like can be used as the p-type dopant. A photoresist is applied to this surface, and a resist mask 113 is formed in the shape of the resonator by photolithography. Here, any shape such as a circle and a rectangle can be selected as the shape of the resist mask.

Using this resist mask 113 as a mask, p
Resonator protrusion (air post) etched by reactive ion beam etching etc. halfway through the mold spacer layer 105
108 is formed (FIG. 2 (b)). Here, the p-type spacer layer 105
, But may be etched to an arbitrary depth up to n-DBR102. A larger etching depth is better for heat dissipation, but it is better to stop above the active layer to protect the active layer 104. This may be determined according to the application. Here, the width (diameter) of the air post 108
Is about 8 μm.

Next, the air post portion _{108 (H 2 S0 4 + H} 2 0 2 + H
Wet-etch in ₂₀ ). In this wet etching, a layer having a higher Al composition has a higher etch rate.
Is etched preferentially, and unevenness 109
Is formed. DBR is Al _x Ga _1-x As if it is formed at a high layer of Al concentration is preferentially etched also annular unevenness is formed. In this case, since the surroundings of the air post are air, the concave portions are formed to have a depth of about 80 nm below the convex portions.

Further, for example, for x = 0.12, x = 0.96
When a DBR is composed of two Al compositions, the Al high concentration layer is selectively oxidized by wet oxidation such as steam oxidation at 300 to 400 ° C., and using this oxidized portion as a mask, (H ₂ S ₄ + H
The _{2 0 2 + H 2 0)} , can be formed irregularities by preferentially wet etched a layer of x = 0.12.

When the composition of each of the layers 123 and 124 of the DBR is uniform, the uneven structure formed by wet etching has a substantially rectangular uneven cross section as shown in FIG.

When the composition change of each layer is continuously changed,
Irregularities such as a sine curve that changes smoothly can also be formed. For example, Al _0.96 Ga _0.04 As125 and Al _0.12 Ga
_0.88 As127 is connected with graded-index (x: 0.96 → 0.12) Al concentration change layer 128, and Al _0.12 Ga _0.88 As127 and Al _0.96 Ga _0.04 As12
When DBR is formed by connecting 5 with a graded-index (for example, x: O.12 → 0.96) Al concentration change layer 126, smooth unevenness can be formed (FIG. 11).

When the air around the air post 108 is air,
The higher the heat dissipation effect is, the more the recessed portion is recessed as much as possible. However, when the surroundings of the air post are buried as described later, it is preferable to keep the unevenness step to about the thickness of the DBR1 layer in order to ensure contact with the buried layer (see FIG. 10).

Next, after removing the resist mask 113 (FIG. 2C), a part of the surface excluding most of the air post 108 is formed.
On the (bottom), for example, a SiO ₂ film is formed as the insulating film 112 by a plasma CVD method using monosilane as a raw material.
Then, the upper electrode 110 is continuously formed along the upper surface contact layer 107 of the air post 108, the air post side wall unevenness 109, and the surface of the insulating layer 112 (FIG. 2D). As a film forming method, a sputter evaporation method, an electron beam evaporation method, or the like can be used.

As the material of the upper electrode 110, Ti is preferable because it is a material that can make ohmic contact with the compound semiconductor. In addition, an AuGe alloy can be used for an n-type compound semiconductor, and an AuZn alloy can be used for a p-type compound semiconductor. Alternatively, Ti and Au may be sequentially stacked in this order by a sputter deposition method. When Au is formed on the outermost surface of the electrode, an oxide film is not formed, and when a buried layer is formed thereon, Au is preferable as a material having excellent wettability with this buried layer (a material having good adhesion). It is.

Finally, AuGe, Ni, and Au are laminated on the back side of the substrate 101 by vapor deposition to form the lower electrode 111. Then, annealing (400 ° C., 2 minutes, in an Ar atmosphere) is performed for electrode contact, and a surface-emitting type semiconductor laser is manufactured (FIG. 2D). The completed surface emitting laser had improved output and stable oscillation intensity.

(Second Embodiment) The structure of the second embodiment is a structure in which the periphery of an air post having a concavo-convex structure on the side wall is buried with an insulating film, and an upper electrode is formed thereon.

FIG. 3 shows this surface emitting laser structure. This structure is the same as the above-described structure except for the buried layer 114 and the upper electrode 116.
It has the same configuration as 1. Therefore, the same parts as those in FIG. 1 are denoted by the same reference numerals. Buried layer 114 is preferably a high thermal conductivity in the insulating film, Al ₂ 0 _3, AlN, it is material composed mainly of such AlGaN is preferred. If the unevenness 109 on the side wall of the air post 108 is too large, it is difficult to make contact with the buried layer.
It is preferable that the thickness be kept to about the film thickness per layer.

The structure of this embodiment is manufactured as follows. The fabrication method is shown in FIG. Steps until the unevenness is formed on the side wall of the air post 108 and the unevenness structure 109 is formed (FIG.
(c)) is the same as in the first embodiment. However, the step of the unevenness was 50 nm.

Next, the air post 108 is embedded with the insulating film 114 (FIG. 4D). The method of forming the insulating film 114 is a CVD method for improving the adhesion with the uneven structure 109 formed on the side wall of the air post.
Etc. are suitable. The material is Al ₂ O ₃ , A
A material mainly containing 1N, AlGaN, or the like is preferable. Then, performs patterning of the buried layer and the like Si0 ₂ mask 115, to form a laser emitting unit (Figure 5 (a)). Further, an upper electrode 116 is formed by stacking Ti and Au so as to be in contact with the upper contact layer 107. Finally, the substrate 101
AuGe, Ni, Au are deposited on the back side by vapor deposition to form the lower electrode 111, and annealed for electrode contact (400 ° C, 2 ° C).
(In an Ar atmosphere) to produce a surface emitting semiconductor laser (FIG. 5B).

The surface emitting laser completed in this way had an improved output and a stable oscillation intensity. According to the present embodiment, the air post 108 having the uneven structure 109 on the side wall is closely covered with the buried layer 114 having excellent heat conduction, so that the heat radiation property is further increased, and the element temperature during driving can be greatly reduced. did it. As a result, a significant increase in laser output and improvement in reliability were realized.

Third Embodiment A third embodiment is a surface-emitting laser in which the periphery of an air post having an uneven structure on the side wall is embedded with an insulator and a metal, and an upper electrode is formed thereon. .

FIG. 6 shows a surface emitting laser having this structure. The air post 108 is formed up to the n-type spacer layer 103. This structure is similar to the above-described structure except for the insulating layer 117, the upper electrode 118, the buried layer 119 made of metal, and the extraction electrode 120.
It has the same configuration as 3. 3 are denoted by the same reference numerals.

[0061] The insulating layer 117 for the buried layer 119 is higher material preferably thermal conductivity, as previously described Al ₂ 0 _3, AlN, Al
Material mainly composed of GaN or the like but is suitable, since the film thickness is thin compared to the buried layer 114 of the structure of the second embodiment described above, other insulating material (for example, Si0 _2, Ti0 _2, Ta ₍₂ 0 ₃ etc.)
May be. The metal film 119 of the buried layer may be made of any material as long as it is a metal. In addition to AuSn, Sn, In, SnIn, PbSn, AuSi
Specific examples include, but are not limited to, these.
Also in this case, it is desirable that the depression of the concave portion of the air post 118 with respect to the convex portion is kept within a range of about the film thickness per DBR layer. In this structure, the insulating film 117 prevents the element from being electrically short-circuited. Further, by using the metal film 119 as a buried layer for the air post 108, a higher heat radiation effect can be achieved.

The main heat source in the surface emitting semiconductor laser having the air post structure is, as described above, the active layer 104 and the p-DBR 10.
6 or Joule heat due to the contact resistance between the p-type contact layer 107 and the upper electrode.
These heat sources mainly exist in the air post 108.
Therefore, the uneven structure 109 is formed on the side wall of the air post 108 as described above.
Is provided to increase the surface area, or to increase the contact area between the air post and the buried layer acting as a heat sink around the air post, thereby promoting heat radiation of the air post. In this way, the temperature of the resonator was lowered, and as a result, a significant increase in laser output and improvement in reliability were realized.

FIGS. 7 and 8 show a manufacturing method of the third embodiment. The steps from the formation of the air post 108 to the formation of the concavo-convex structure 109 on the side wall thereof are the same as those in the method of manufacturing the structure of the first and second embodiments (FIGS. 7A to 7C). However, the etching is performed up to the n-spacer layer 103 here.

Next, on the surface excluding the upper part of the air post 108, for example, a SiO ₂ film is formed as an insulating layer 117 by a plasma CVD method using monosilane as a raw material (FIG. 7 (d)).
Then, an upper electrode 118 is formed continuously by CVD along the upper surface contact layer 107 of the air post 108, the air post side wall unevenness 109, and the surface of the insulating layer 117 (FIG. 8A). Here Au
Was formed. However, the upper electrode 118 is brought into contact with the end of the upper contact layer 107, and the upper electrode of the laser emission port at the center is removed by photolithography (FIG. 8).
(a)). Materials suitable for use are in accordance with the description of the manufacturing method in the above embodiment.

On this upper electrode 118, a buried layer 119 made of metal is deposited by a lift-off method. AuSn alloy was used as the material of the buried metal 119. Besides, metals such as Sn, In, SnIn alloy, PbSn alloy, and AuSi alloy can be used. The buried metal 119 is then melted and deformed by the heat treatment, thereby forming the upper electrode 11.
A buried layer having good adhesion to 8 (FIG. 8 (b).
A on the surface of the buried layer 119 so that it does not touch the laser emission port.
u electrode pad 120, and AuGe, Ni, A
A lower electrode 111 having a structure in which u were laminated was deposited and annealed (400 ° C., 2 minutes, in an Ar atmosphere) for electrode contact, thereby producing a surface-emitting type semiconductor laser (FIG. 8C).

According to this embodiment, the air post 108 having the uneven structure 109 on the side wall is closely covered with the buried metal layer 119 having excellent heat conductivity, so that the heat radiation property is enhanced and the element temperature during driving is increased. Could be lowered. As a result, a significant increase in laser output and improvement in reliability were realized.

(Fourth Embodiment) The fourth embodiment has a structure in which a current confinement layer is added to the structure of the third embodiment. A method for manufacturing the structure of the fourth embodiment will be described with reference to FIGS. 7, 8, and 9. FIG.

Here, the DBR is set to Al _0.15 Ga _O.85 As and Al _O.95 Ga
_A layer 105 made of Al _O.96 Ga _0.04 As / AlAs / Al _0.96 Ga _0.04 As is formed by alternately laminating _0.05 As, under the p-DBR 106.
Is provided. Then, up to the air post 108 is formed by the same manufacturing method as in the third embodiment (see FIGS. 7A and 7B).

Next, the device was placed in water vapor at 400 ° C. for 10 minutes to obtain Al _0.95 Ga _0.05 As and Al _O.96 Ga _O.04 As / A.
lAs / Al _0.96 Ga _0.04 As is selectively oxidized. By this oxidation treatment, a layer 10 of Al _0.96 Ga _0.04 As / AlAs / Al _0.96 Ga _0.04 As
In 5, the oxide layer 122 is formed with a width of about 2.5 μm from both sides of the side wall of the air post 108, and the current confinement part 121 is formed.
Furthermore, the Al _0.95 Ga _O.05 As layer of p-DBR106 is Al _O.15 Ga _0.95 As
Since it is more oxidized than the layer, when wet-etched with (H ₂ S 0 ₄ + H ₂ 0 ₂ + H ₂ 0), the Al _O.95 Ga _O.05 As layer is almost etched by being masked by the _oxide layer. Al _0.15 Ga
_{The O.95} As layer is etched. Thus, air post 10
An uneven structure 109 can be formed on the side wall of FIG. 8 (FIG. 7 (c)
reference).

After the formation of the insulating layer 117 on the surface excluding the upper part of the air post 108 (FIG. 7D), the formation of the electrode pad 120 on the surface of the buried layer 119 and the formation of the lower electrode on the back side of the substrate 101
The steps up to the formation of 111 (FIG. 8 (c)) are the same as in the third embodiment.

According to this embodiment, the buried layer 1 having excellent heat conduction is formed around the air post 108 having the uneven structure 109 on the side wall.
By covering closely with 19, the heat dissipation was enhanced, and the element temperature during driving could be greatly reduced. In addition, the injected current is concentrated in the center of the air post, significantly reducing reactive current compared to a simple protruding air post structure, reducing threshold current, significantly increasing laser output, and improving reliability. Was realized. Thus, the Al oxide layer 122
When the present invention is applied to a protruding resonator structure using as a current confinement layer, current confinement and heat radiation, which were not possible in the past, can be achieved at the same time, which is extremely effective.

The present invention can be variously modified within the scope of the present invention. The active layer is made of InGa according to the oscillation wavelength of a semiconductor light emitting device such as a surface emitting semiconductor laser.
As, GaAs, AlGaAs, GaInP, AlGaInP, InGaAsP, ZnSe, Z
It is possible to use a single layer or a quantum well layer made of any of nS, GaN, AlGaN, InN, and InGaN. further,
The present invention can be implemented even if the conductivity type of the semiconductor is changed from the p type to the n type. When the active layer is formed of InGaAs or GaAs, the oscillation wavelength can be set to about 980 nm, so that light can be emitted from the GaAs substrate side.

A structure in which a current confinement structure is added to each of the structures of the first to third embodiments is also possible. For example, a layer that is easier to oxidize than the other layers is inserted into the DBR (AlAs, Al _x Ga _1-x As, x = 0.96, etc.), and this is oxidized by wet oxidation to provide a current confinement structure Yes (see Figure 9). At this time, the structure is such that the interval between the current paths of the current constriction portion is smaller than the interval between the opposing concave portions on the side wall of the air post. By adopting such a structure,
The influence of the uneven structure provided on the side wall of the air post scattering light in the element can be avoided. As described above, when the present invention is applied to a surface emitting laser having a current confinement structure, the threshold value of the element can be reduced, and the characteristics can be improved and stabilized, in addition to the improvement of the heat radiation efficiency due to the uneven structure of the air post sidewall. It is on the street. Note that the current confinement structure is not limited to one location, and can be formed in any number and in any location.

(Fifth Embodiment) The semiconductor light emitting device such as the surface emitting laser described above can be applied to an optical recording apparatus using the semiconductor light emitting device as a light source. For example, a laser beam printer is an example.

In the fifth embodiment, the above-described surface emitting laser is applied to a laser beam printer. FIG. 12 shows the simple configuration. Here, the light source 130 may be a single surface emitting laser or a so-called multi-array in which a plurality of surface emitting lasers are arranged. In a laser beam printer in which a surface emitting laser according to the present invention is formed into a multi-array and provided as a light source, as shown in FIG. Printing is possible. The pitch on the drum 133 can be set to an arbitrary width by the lens system 134. For example, the light of the surface emitting laser array having a pitch of 125 μm can be easily set to a pitch of 20 μm on the drum surface 133. In terms of control, a one-dimensional integrated surface emitting laser with eight lasers is easy to use. Here, a laser wavelength of 0.77 μm was used. Reference numeral 132 denotes a light receiver for receiving a scanning beam in order to set the operation timing of the LD control circuit.

In order to increase the speed of the laser beam printer, there is a limit to the increase in the number of revolutions of the polygon mirror 131, and the use of the multi-array surface emitting laser according to the present invention can easily increase the speed. In addition, when the edge emitting lasers are arrayed, there is a slight problem of an increase in power consumption due to a large amount of injected current. However, if the surface emitting laser according to the present invention is used, power consumption can be reduced by one digit or more. Can be. This is because the driving current of the edge emitting laser is 50 mA, whereas the surface emitting laser can be driven at about 10 mA. However, when the present invention is applied to an edge emitting laser, the problem of heat dissipation is reduced. further,
If the number of arrays is increased to about 1200 pixels, a high-speed laser beam printer can be constructed simply by scanning a multi-array light source without a polygon mirror.

[0077]

As described above, according to the present invention,
By forming the concavo-convex structure on the side wall of the protruding portion such as the protruding resonator, the surface area can be increased and the heat radiation effect of the semiconductor light emitting element can be improved. In addition, by increasing the contact area with the high heat dissipation material embedded in the surrounding area, the heat dissipation is dramatically improved, the rise in the element temperature during driving is suppressed, and the light output is improved. Properties and stability can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a surface emitting laser according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a step of manufacturing the surface-emitting laser according to the first embodiment.

FIG. 3 is a sectional view showing a surface emitting laser according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view illustrating a step of manufacturing the surface-emitting laser according to the second embodiment.

FIG. 5 is a cross-sectional view illustrating a step of manufacturing the surface-emitting laser according to the second embodiment.

FIG. 6 is a sectional view showing a surface emitting laser according to a third embodiment of the present invention.

FIG. 7 is a sectional view illustrating a step of manufacturing the surface emitting laser according to the third embodiment.

FIG. 8 is a cross-sectional view illustrating a step of manufacturing the surface-emitting laser according to the third embodiment.

FIG. 9 is a cross-sectional view illustrating a surface emitting laser having a current confinement structure according to a fourth embodiment of the present invention.

FIG. 10 is a diagram illustrating an example of a concavo-convex structure of a protruding resonator side wall.

FIG. 11 is a diagram showing another example of the concavo-convex structure of the protruding resonator side wall.

FIG. 12 is a schematic diagram illustrating a laser beam printer using a semiconductor light emitting device according to the present invention as a light source.

FIG. 13 is a sectional view showing a conventional surface emitting laser.

FIG. 14 is a cross-sectional view showing another conventional surface emitting laser.

[Explanation of symbols]

101 n-GaAs substrate 102 n-DBR 103 n-spacer layer 104 active layer 105 p-spacer layer 106 p-DBR 107 p-contact layer 108 protruding resonator (air post) 109 concavo-convex structure on air post side wall 11O, 116,118 anode electrode (Upper electrode) 111 lower electrode 112,117 insulating film (insulating layer) 113 resist mask 114 buried layer 115 Si0 ₂ mask 119 metal buried layer 120 electrode pad 121 current confinement part 122 oxide layer 123 GaAs 124 AlAs 125 AlGaAs high concentration Al layer 126 Al concentration change layer of AlGaAs (small → many) 127 AlGaAs low concentration layer 128 AlGaAs Al concentration change layer (many → small) 130 Light source composed of semiconductor light emitting device according to the present invention 131 Polygon mirror 132 Light receiver 133 Photosensitive drum 134 Cylindrical lens

Claims (26)

[Claims] 1. A semiconductor device having a protrusion-like structure processed into a protrusion, wherein a part or all of a side wall of the protrusion-like structure is formed with an uneven structure for heat radiation. 2. A semiconductor light emitting device having a protruding resonator structure processed into a protruding shape, wherein the heat dissipation uneven structure is formed on a part or all of side walls of the protruding resonator structure. Item 2. The semiconductor element according to item 1. 3. An active layer, and a p-type distributed black reflector and an n-type distributed black reflector having a laminated structure in which a pair of layers having different compositions and provided so as to sandwich the active layer are repeatedly laminated. 3. The semiconductor device according to claim 2, wherein a part or all of the semiconductor element is configured as a surface emitting laser having the air post-shaped projection structure. 4. The semiconductor device according to claim 3, wherein the layers forming the pair having different compositions have a uniform composition in each layer. 5. The semiconductor device according to claim 3, wherein the composition of the layers forming the pair having different compositions changes continuously in each layer. 6. The uneven structure formed as an uneven structure in which annular unevenness formed using the laminated structure is overlapped along a side wall of the distributed Bragg reflector in the protruding structure. 6. The semiconductor device according to 3, 4, or 5. 7. A Fabry-Perot type, a DFB type, or a D type
3. The semiconductor device according to claim 2, wherein the semiconductor device is configured as a BR type edge emitting semiconductor laser, and the projecting resonator structure is a stripe-shaped mesa structure. 8. The semiconductor device according to claim 1, wherein the semiconductor device is configured as a semiconductor light receiving device having the protruding structure. 9. The semiconductor device according to claim 1, wherein said uneven structure is formed by forming a rough surface on a side wall of said protruding structure by anodizing treatment. 10. The semiconductor device according to claim 1, wherein said uneven structure is formed by mechanically rubbing a side wall of said projecting structure with an abrasive. 11. The semiconductor device according to claim 1, wherein said uneven structure is formed by forming a rough surface on a side wall of said protruding structure by plasma etching. 12. The method according to claim 1, wherein the protruding structure is buried in a layer mainly composed of Al ₂ O _3, AlN or AlGaN.
12. The semiconductor element according to any one of claims 11 to 11. 13. An air post-shaped distributed Bragg reflector having at least an air post-shaped distributed Bragg reflector, wherein an insulating film is provided so as to electrically insulate the p-type distributed Bragg reflector and the n-type distributed Bragg reflector provided so as to sandwich the active layer. 7. The semiconductor device according to claim 3, wherein an electrode metal film is provided on the insulating film so as to be in contact with the side wall. 14. The semiconductor device according to claim 1, wherein an appropriate insulating layer is formed, and said protruding structure is buried with a metal burying layer.
2. The semiconductor device according to claim 1. 15. The semiconductor device according to claim 1, wherein the semiconductor device is configured as a semiconductor light emitting device having an active layer, and further has a current confinement structure for narrowing a current path to the active layer. . 16. A concavo-convex structure provided on a side wall of the distributed Bragg reflector, further comprising a current confinement structure for narrowing a current path to the active layer, wherein an optical path width limited by the current confinement structure is provided on a side wall of the distributed Bragg reflector. 7. The semiconductor device according to claim 6, wherein the distance between the concave portions facing each other in the in-plane direction is smaller. 17. An optical recording apparatus which performs recording on an optical recording medium using the semiconductor light emitting device according to claim 1 as a light source. 18. An optical recording apparatus according to claim 17, wherein said light source comprises a plurality of surface emitting lasers. 19. A p-type distributed black reflector and an n-type distributed black reflector having an active layer, and a laminated structure in which a pair of layers having different compositions and provided so as to sandwich the active layer is repeatedly laminated. A method for manufacturing a surface emitting laser in which a part or all of the surface has a protruding structure in the form of an air post. Forming a concavo-convex structure. 20. The method of manufacturing a surface emitting laser according to claim 19, wherein said air post-shaped projection structure is formed by dry etching. 21. The method according to claim 19, wherein the uneven structure is formed by wet etching. 22. The surface emitting laser according to claim 21, wherein the paired layers having different compositions have different Al concentrations, and the unevenness is formed on the side wall of the distributed Bragg reflector using the difference in Al concentration. Manufacturing method. 23. A layer forming a pair having a different composition has a different Al concentration. An oxidized portion is formed on a side wall of the distributed Bragg reflector using the difference in the Al concentration, and then wet etching is performed using the oxidized portion as a mask. 3. An uneven structure is formed by using
2. The method for manufacturing a surface emitting laser according to item 1. 24. The surface emitting laser according to claim 22, wherein the layers forming the pairs having different compositions have a uniform composition in each layer, and the uneven structure is formed as an uneven structure having a substantially rectangular cross section. Manufacturing method. 25. The layer forming a pair having a different composition, wherein the composition of each layer changes continuously, and the uneven structure is formed as an uneven structure whose cross section changes substantially in a sine curve shape. 24. The method for manufacturing a surface emitting laser according to 23. 26. The method of manufacturing a surface emitting laser according to claim 19, further comprising a step of burying an insulator or a metal around the air-post distributed Bragg reflector.