JPH10261830A - Surface emitting type semiconductor laser and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a heat sink structure, wherein the surface emission of a laser is enabled, by a simple method not comprising a process, which deteriorates an element, and to make it possible to obtain the high output of the laser and the high reliability of the laser by a method wherein a buried metal film consisting of a metal of a melting point of a specified temperature or lower is buried in the periphery of a projection-shaped resonator. SOLUTION: An insulating film 109 consisting of an SiO2 film and an upper electrode 110, which consists of the two layers of a Ti film and an Au film, are formed on the periphery of a resonator projection part 108. A buried metal film 112 is formed on the periphery of the projection part 108 in such a way as to adhere closely to the surface of this electrode 110. The buried metal film 112 is a film consisting of of an AuSn alloy of a melting point of 190 deg.C and is formed in a thickness thicker than the height of the projection part 108. As the buried metal film, a film consisting of a metal of a melting point of 400 deg.C or lower, such as Sn, In, an SnIn, a PbSn and an AuSi, can be used in addition to the film consisting of the AuSn alloy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-emitting type semiconductor laser which emits a laser beam in a direction perpendicular to a substrate.

[0002]

2. Description of the Related Art A conventional surface emitting semiconductor laser is disclosed in IEE, Journal of Quantum Electronics, Vol. 27, No. 6, 1991.
Year) pages 1332 to 1346 [IEEE Jou
rnal of QuantumElectronic
s, vol. 27, no. 6 pp1332-1346
(1991)], Jack L. It is summarized in detail and systematically in a commentary article by Jewel et al.

[0003] In general, the main factor that limits the output of a semiconductor laser or impairs its reliability is a rise 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 heat radiation by directly contacting an element forming portion with a heat sink has become a common means.

However, in the case of the surface emitting type semiconductor laser of the surface emitting type, since the laser is 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, so that the heat radiation is difficult. I had it.

To solve this problem, for example, Japanese Patent Application Laid-Open No. 5-283796 has an electrode having a heat sink function. It is considered that the main heat source in the surface emitting semiconductor laser having such a protruding resonator structure is Joule heat due to the resistance of the p-type semiconductor multilayer reflective layer or the contact resistance between the p-type contact layer and the upper electrode. Can be These heat sources mainly exist on the resonator protrusions. Therefore, by closely covering the periphery of the resonator protrusion with a metal having excellent heat conduction, there is a possibility that the heat dissipation is increased and the element temperature can be significantly reduced.

In order to emit a laser beam from the surface, only the periphery of the cavity projection must be buried with metal, and the top surface of the cavity projection having the laser emission portion must be formed so as not to be covered with metal. In the above-described method, a metal is deposited only on an exposed metal portion by using a plating method, so that the laser emission port on the upper surface of the resonator protrusion is secured while embedding the metal around the resonator. Gold and the like are mentioned as the material.

[0007]

In order to deposit a metal only on an exposed metal portion by using a plating method as in the above-described method, an electrolytic plating method must be used. This puts the conductive plating object and the electrode in the electrolytic solution containing metal ions,
This is a method in which a metal is deposited on the anode by passing an electric current using the object to be plated as the anode. Since metal ions in the electrolytic solution are negative ions, they are attracted to the anode and come into contact therewith, lose electrons and become neutralized, and are deposited as a metal film on the surface of the anode to be plated. However, since the treatment in the electrolytic solution is necessary, there is a possibility that the semiconductor element may be contaminated with impurities. In addition, there is a problem in that a current flows through the element, thereby deteriorating the characteristics of the element.

An object of the present invention is to provide a surface emitting semiconductor laser having a high laser output and high reliability by realizing a heat sink structure capable of emitting light from the surface by a simple method not including a step of deteriorating the element. To provide.

[0009]

According to a first aspect of the present invention, there is provided a vertical cavity surface emitting semiconductor laser having at least a part of a projecting resonator, wherein a melting point is provided around the projecting resonator. Is that the buried metal of 400 ° C. or less is buried.

According to the second aspect of the present invention, it is defined that the embedded metal is a metal or an alloy that forms a solid solution with gold. By using a metal or alloy that forms a solid solution with gold, the wettability of the upper electrode and the buried metal is improved in the burying metal melting step, and the adhesion is increased.

According to a third aspect of the present invention, it is defined that an electrode pad made of gold is formed on a part of the surface of the buried metal. As a result, the metal wire connected for current supply can also function as a heat sink.

A fourth aspect of the present invention defines a method for manufacturing a surface emitting semiconductor laser according to the first aspect. In this method, a step of forming an upper electrode having an opening on the upper surface of the resonator projection, a step of forming an embedded metal having a melting point of 400 ° C. or less around the resonator projection, Performing a heat treatment to melt the embedded metal.

A feature of the invention according to claim 5 is that the step of performing a heat treatment at a temperature equal to or higher than the melting point of the embedded metal to melt the embedded metal is performed under a reduced pressure condition of 1000 Pa or less. As a result, it is possible to suppress the generation of voids at the time of embedding, and to enhance the adhesion between the cavity projection and the embedding metal.

A feature of the invention according to claim 6 is that, in the step of performing a heat treatment at a temperature equal to or higher than the melting point of the embedded metal and melting the embedded metal, the temperature is increased and the embedded metal is melted under a reduced pressure condition of 1000 Pa or less. That is, the temperature is reduced under the atmospheric pressure condition. As a result, the generation of voids at the time of embedding can be further suppressed, and the adhesion between the cavity projection and the embedding metal can be further increased.

[0015] The feature of the invention of claim 7 is the following.
6. The method according to claim 6, further comprising a step of performing a plasma cleaning process prior to the step of performing a heat treatment to a temperature equal to or higher than the melting point of the embedded metal to melt the embedded metal. Thus, poor adhesion can be suppressed by increasing the wettability between the upper electrode and the embedded metal.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 Hereinafter, an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a sectional view schematically showing a surface emitting semiconductor laser according to the present invention. This surface-emitting type semiconductor laser has an n-type semiconductor multilayer reflective layer 102 on an n-type GaAs substrate 101.
, An n-type cladding layer 103, an active layer 104, a p-type cladding layer 105, a p-type semiconductor multilayer reflective layer 106, and a p-type contact layer 107 are sequentially laminated.

The cavity projection 108 is etched through the p-type contact layer 107 and the p-type semiconductor multilayer reflective layer 106 to a part of the p-type cladding layer 105 so as to project.
Are formed. By forming the resonator projection, the injected current can be spatially confined, and efficient laser oscillation can be achieved.

Around the resonator projection 108, an insulating film 109 made of a SiO2 film and an upper electrode 110 made of two layers of a Ti film and an Au film are formed. The insulating film 109 is formed so as to cover at least the surface of the p-type cladding layer 105, and the upper electrode 110 is formed of the insulating film 109 and the resonator protrusion 10.
Eight side surfaces and the surface of the p-type contact layer 107 are continuously formed. Further, the upper electrode 110 has a laser emission port 111 on the upper surface of the resonator projection 108. The laser emission port is an opening on the upper surface of the resonator projection 108 of the upper electrode 110, from which laser light is emitted toward the surface of the substrate.

The buried metal 11 is formed around the resonator projection 108 so as to be in close contact with the surface of the upper electrode 110.
2 is formed, and Au is not blocked from the laser emission port 111.
Electrode pad 113 is formed. n-type GaAs
On the back surface of the substrate 101, a lower electrode 114 made of AuGe, Ni, or Au is formed.

Here, the n-type semiconductor multilayer reflective layer 102
30 pairs of lAs and Al _0.15 Ga _0.85 As are alternately stacked and have a reflectivity of 99.9% or more with respect to the laser oscillation wavelength.

The p-type semiconductor multilayer reflective layer 106 is made of AlAs
And Al _0.15 Ga _0.85 As are alternately laminated in 25 pairs and have a reflectance of 99.6% or more with respect to the laser oscillation wavelength.

The active layer 104 is a multiple quantum well active layer composed of three GaAs well layers and an Al _0.3 Ga _0.7 As barrier layer sandwiched therebetween.

The p-type contact layer 107 is made of a GaAs layer having a carrier concentration of 1 × 10 ¹⁹ cm ⁻³ or more.

The upper electrode 110 is formed of a Ti thin film and an Au thin film.
The Au thin film faces the side in contact with the buried metal 112.

The buried metal 112 has a melting point of 190.degree.
It is a uSn alloy and is formed to a thickness exceeding the height of the resonator projection 108. AuSn as embedded metal
In addition, a metal having a melting point of 400 ° C. or less such as Sn, In, SnIn, PbSn, and AuSi can be used. In the present invention, a heat treatment step at a temperature equal to or higher than the melting point is required in order to bury the resonator protrusions with good adhesion by melting the buried metal. If the temperature is 400 ° C. or higher, there is a possibility that unexpected diffusion of the dopant or the like may occur. This temperature is preferably as low as possible, and more preferably a metal having a melting point of 300 ° C. or less is used.

The main heat source in the surface emitting semiconductor laser having the projecting resonator structure as in the present embodiment is the resistance of the p-type semiconductor multilayer reflective layer 106 or the p-type contact layer 107.
It is considered that Joule heat due to the contact resistance of the upper electrode 110 and the upper electrode 110, and these heat sources mainly exist in the resonator protrusion 108. According to the present invention, the buried metal 112 having excellent heat conduction is formed around the resonator protrusion 108.
By covering in close contact, the heat dissipation was enhanced and the element temperature could be reduced. As a result, a significant increase in laser output and improvement in reliability were realized.

In the present invention, the Au electrode pad 113 is used.
Is formed on the surface of the buried metal 112 so that a metal wire connected to the electrode pad 113 for current supply can also function as a heat sink.
Heat dissipation can be further improved.

Next, the manufacturing method will be described with reference to FIGS. First, as shown in FIG.
1 and an n-type semiconductor multilayer reflective layer 102 and an n-type clad layer 1
03, an active layer 104, a p-type cladding layer 105, a p-type semiconductor multilayer reflective layer 106, and a p-type contact layer 107 are sequentially epitaxially grown by metal organic chemical vapor deposition. Selenium was used as an n-type dopant, and zinc was used as a p-type dopant. Then, a photoresist is applied to the surface, and a resist mask is formed in the shape of the resonator by a photolithographic method. Here, an arbitrary shape such as a circle, a rectangle, and a stripe can be selected as the shape of the resist mask.

Next, as shown in FIG. 3, using the resist mask as a mask, the resonator protrusion 108 is formed by reactive ion beam etching using a gas such as chlorine to a part of the p-type cladding layer 105. Then, after removing the resist mask, an SiO2 film, for example, is formed as an insulating film 109 on the surface by a thermal CVD method using monosilane as a raw material. Here, the etching is performed to a depth of about 5 μm halfway through the p-type cladding layer 105, but the etching may be performed to any depth.

Next, as shown in FIG. 4, a resist is applied to the surface. The applied resist tries to be as flat as possible due to surface tension. Therefore, the resonator projections 108
The thickness of the upper resist is smaller than elsewhere.

Next, as shown in FIG. 5, the resist is selectively removed by an ashing method, and is partially exposed to the cavity projection 108 covered with the insulating film 109, and then a reactive gas such as CF4 is used. By reactive ion etching,
The exposed insulating film 109 is removed. Ashing method
This is a method of selectively removing resist using a gas having a high oxidizing power such as oxygen radicals in ozone. Since damage to a semiconductor such as sputtering is small, it is widely used for removing a resist mask or the like. Since the ashing proceeds isotropically with respect to the resist, the thin resist of the resonator projection 108 disappears first. Here, at least the upper surface of the resonator projection 108, more preferably the resonator projection 108
Expose all of the sides. Since the purpose of this step is to remove only the insulating film of the resonator projection 108,
It is not preferable that the surface other than the resonator projection 108 is exposed.

Next, as shown in FIG. 6, ashing is performed again to completely remove the remaining resist.
8 Form a photoresist mask of desired shape on the upper surface,
After the upper electrode 110 is deposited by a vacuum deposition method, ultrasonic vibration is applied in an organic solvent such as acetone to remove the upper electrode film deposited on the surface of the resist mask together with the resist mask. This method is generally called a lift-off method.
Thus, the upper electrode 110 has the laser emission port 111 on the upper surface of the resonator, and the periphery of the resonator projection 108 and the insulating layer 10.
9 is formed continuously along the surface of the substrate. Here, as the upper electrode 110, titanium is 0.1 μm and gold is 0.1 μm.
Each was laminated. The titanium layer is a material that can make ohmic contact with a resonator made of a compound semiconductor. In addition, an AuGe alloy can be used for an n-type semiconductor, and an AuZn alloy can be used for a p-type semiconductor. it can. Gold was selected as a material having excellent wettability with an embedded metal described later. If an oxide film is formed on the surface of the upper electrode 110, the wet buried metal is repelled and the wettability is deteriorated. Gold is the most excellent material for forming an oxide film.

Next, as shown in FIG. 7, a resist mask is formed so as to completely cover at least the laser emission port 111 and at least 1 μm from the end of the laser emission port 111 or within 5 μm from the side surface of the cavity projection 108, and the buried metal 112 is formed. Then, an AuSn alloy is deposited to a thickness of 6 μm by a vacuum evaporation method. As the buried metal, in addition to the AuSn alloy, Sn, I
Metals having a melting point of 400 ° C. or less such as n, SnIn alloy, PbSn alloy, and AuSi alloy can be used. Here, the vacuum evaporation method is used, but it goes without saying that a sputtering method or the like can be used in addition to this. The thickness of the buried metal 112 is preferably equal to or greater than the height of the resonator projection 108.

Next, as shown in FIG. 8, ultrasonic vibrations are applied in an organic solvent such as acetone to dissolve the resist mask and to remove the buried metal deposited on the resist mask. In this manner, a buried metal 112 having a thickness of 6 μm is deposited and formed around the resonator projection 108. At this time, depending on how the resist mask pattern is selected, a gap of at most 5 μm may exist between the resonator projection 108 and the buried metal 112, but this does not pose a problem for the reason described later. However, the gap is desirably 5 μm or less. Also, burrs and the like may be generated at the edge of the buried metal 112. However, if the edge of the buried metal 112 is separated from the end of the laser emission port 111 by 1 μm or more, there is no problem for the reason described later.

Then, in order to clean the exposed surface of the upper electrode 110, the substrate surface is subjected to argon plasma cleaning. As a result, dirt such as organic substances on the exposed surface of the upper electrode 110 can be more completely removed, and the wettability to the embedded metal can be further increased. Here, argon plasma is used in order to minimize damage to the laser emission port 111 on the upper surface of the resonator projection 108, but oxygen plasma, reactive gas plasma, or the like may be used.
In that case, it is necessary to pay attention to the plasma density and the processing time so as to reduce the damage.

Next, as shown in FIG. 9, a heat treatment is applied to melt the buried metal 112, and bury the periphery of the resonator projection 108 in close contact with the upper electrode 110. As a heat treatment method, first, the substrate is placed in a reduced pressure of 1000 Pa or less, and the temperature is raised to 200 ° C., which is slightly higher than 190 ° C. of the melting point of the embedded metal AuSn alloy. When the temperature is stabilized, argon gas is slowly supplied to normal pressure, and then the temperature is reduced while maintaining the normal pressure state of the argon atmosphere to complete the heat treatment. Even if there is a gap of at most 5 μm between the cavity projection 108 and the embedded metal 112 before the embedded metal is melted, the wettability to the upper electrode 110 is good when the embedded metal 112 is melted and liquefied. The periphery of the resonator projection 108 is completely adhered and buried so as to fill the gap. However, if the gap between the cavity projection 108 and the embedded metal 112 before the embedded metal melting exceeds 5 μm, the air gap may remain after the melting. Therefore, the gap between the cavity projection 108 and the embedded metal 112 before the embedded metal is melted is desirably 5 μm or less.

The adhesion between the upper electrode 110 and the buried metal 112 is caused by surface tension and good mutual wettability, while the wettability of the buried metal 112 to the p-type contact layer 107 exposed at the laser emission port 111 is small. Therefore, the laser emission port 111 on the upper surface of the resonator projection 108 without electrodes is secured without being covered by the embedded metal 112. Also, burrs generated at the edge of the embedded metal 112 are melted and disappear. However, when the edge of the laser emission port 111 and the edge of the buried metal 112 are 1 μm or less, the buried metal sometimes adheres to the laser emission port 111 very rarely. Therefore, the laser emission port 1
1 μm between the edge of the buried metal 112 and the edge of the buried metal 112
It is desirable to separate them by more than this.

By reducing the pressure of the embedded metal to 1000 Pa or less when the embedded metal is melted, it is possible to prevent bubbles from being mixed into the embedded metal 112 and to suppress the generation of voids around the resonator projection 108. Such an effect is not recognized at a pressure exceeding 1000 Pa, and the frequency of generation of voids increases. More preferably, it is 100 Pa or less. Further, the pressure is returned to normal pressure during the melting and the temperature is lowered, whereby the generation of voids can be completely suppressed. Here, an argon gas is used as the atmosphere gas, but an inert gas or a reducing gas may be used. The inert gas referred to here is a rare gas such as helium, neon, argon, krypton, or xenon, or a gas having low reactivity such as nitrogen. Examples of the reducing gas include hydrogen. In this way, it is possible to form the buried metal 112 which has a sufficient thickness, closely adheres to the periphery of the resonator projection 108 without any gap, and has excellent heat dissipation. If the height of the resonator projections 108 and the deposition thickness are made equal, planarization can be achieved. Since the heat treatment temperature is a relatively low temperature of 400 ° C. or less, atomic diffusion hardly occurs, and there is no fear of element deterioration. In our experiment, 4
When the heat treatment was performed at a temperature exceeding 00 ° C., unexpected diffusion of dopants and metal atoms of the upper electrode occurred, and the laser oscillation performance was significantly reduced.

Then, as shown in FIG.
A gold electrode pad 113 is formed on the surface of the buried metal 112 so as not to be caught on the substrate 11. Finally, AuGe,
By depositing the lower electrode 114 on which Ni and Au are stacked, a surface emitting semiconductor laser is completed.

As described above, according to the method for manufacturing a surface emitting semiconductor laser of the present invention, the buried metal is heated and melted at a temperature equal to or higher than the melting point, so that the periphery of the cavity protrusion can be buried in good contact. A self-aligned embedding by the wettability and surface tension of the buried metal and the upper electrode makes it very easy to create a surface-emitting type semiconductor laser with the buried metal without high alignment accuracy when patterning and depositing the buried metal did it. Also,
By selecting a metal having a melting point of 400 ° C. or less as an embedding metal and suppressing the heat treatment temperature in the melting step to 400 ° C. or less, no unexpected deterioration in laser characteristics due to unexpected thermal diffusion of a dopant or the like did not occur.

The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the present invention. The active layer 104 is made of InGaAs, GaAs, or AlGaAs according to the oscillation wavelength of the surface emitting semiconductor laser.
s, GaInP, AlGaInP, InGaAsP, Z
nSe, ZnS, GaN, AlGaN, InN, InG
A single layer or a quantum well layer made of any one of aN can be used, and the present invention can be implemented even if the p-type and the n-type of the conductivity type of the semiconductor are switched.

(Embodiment 2) Next, a second embodiment of the present invention will be described.

FIG. 10 is a sectional view schematically showing a surface emitting semiconductor laser according to a second embodiment of the present invention. This surface emitting semiconductor laser uses an Al oxide layer utilizing natural oxidation of an AlAs layer as a current confinement structure.
Is different from the embodiment.

Hereinafter, this will be described in detail with reference to FIG. This surface-emitting type semiconductor laser comprises an n-type GaAs substrate 201, an n-type semiconductor multilayer reflective layer 202 and an n-type clad layer 20.
3, an active layer 204, a p-type cladding layer 205, a current confinement layer 215, a p-type semiconductor multilayer reflective layer 206, and a p-type contact layer 207 are sequentially stacked.

The resonator projection 208 is formed by etching the p-type cladding layer 205 halfway through the p-type contact layer 207, the p-type semiconductor multilayer reflective layer 206, and the current confinement layer 215.

An insulating film 209 made of a SiO 2 film and an upper electrode 210 made of two layers of a Ti film and an Au film are formed around the resonator projection 208. The insulating film 209 is formed so as to cover at least the surface of the p-type cladding layer 205, and the upper electrode 210 is formed of the insulating film 209 and the resonator protrusion 20.
Eight side surfaces and the surface of the p-type contact layer 207 are formed continuously. Further, the upper electrode 210 has a laser emission port 211 on the upper surface of the resonator projection 208. The laser emission port is an opening on the upper surface of the resonator projection 208 of the upper electrode 210, from which laser light is emitted toward the surface of the substrate.

A buried metal 212 is formed around the resonator projection 208 so as to be in close contact with the surface of the upper electrode 210, and an Au electrode pad 213 is formed so as not to block the laser emission port 211. A lower electrode 214 made of AuGe, Ni, and Au is formed on the back surface of the n-type semiconductor substrate.

Here, the n-type semiconductor multilayer reflective layer 202 is made of A
30 pairs of lAs and Al _0.15 Ga _0.85 As are alternately stacked and have a reflectivity of 99.9% or more with respect to the laser oscillation wavelength.

The p-type semiconductor multilayer reflective layer 206 is made of Al _0.9 G
30 pairs of a _0.1 As and Al _0.15 Ga _0.85 As are alternately stacked and have a reflectance of 99.5% or more with respect to the laser oscillation wavelength.

The active layer 204 is a multiple quantum well active layer comprising three GaAs well layers and an Al _0.3 Ga _0.7 As barrier layer sandwiched therebetween.

The p-type contact layer 207 has a carrier concentration of 1
It is composed of a GaAs layer of × 10 ¹⁹ cm ⁻³ or more.

The current confinement layer 215 is composed of an AlAs layer 216 and an Al oxide layer 217 formed so as to surround the periphery thereof. The Al oxide layer 217 is formed of an AlAs layer 216.
Is naturally oxidized from the side face of the resonator projection 208. As a method thereof, for example, a resonator projection is formed so that at least the AlAs layer is included in the resonator projection,
A method of performing a heat treatment at about 400 ° C. in a steam atmosphere is well known. The AlAs layer 216 has the resonator protrusion 2
Oxidation reaction is caused from the side face 08 toward the inside, and is gradually replaced by the Al oxide layer 217. As a result, AlAs
The layer 216 is continuously surrounded by an Al oxide layer 217 as an insulator.

The upper electrode 210 is made of a Ti thin film and an Au thin film.
Au is in contact with the buried metal 212.

The buried metal 212 is an AuSn alloy having a melting point of 190 ° C., and is formed to have a thickness exceeding the height of the resonator projection 208. AuS as embedded metal
In addition to n, metals having a melting point of 400 ° C. or less, such as Sn, In, SnIn, PbSn, and AuSi, can be used.

This laser differs from the first embodiment in that an Al oxide layer utilizing the natural oxidation of the AlAs layer is used as a current confinement structure.

The current injected from the upper electrode is
Since the layer 217 is an insulator, it is blocked, and
8 flows through the AlAs layer 216 which is a conductor located at the center of the cavity 8 so as to concentrate on the center of the resonator projection 208.
Thus, the current confinement layer 215 functions as a horizontal current confinement structure. Since the injected current is concentrated at the center of the resonator projection 208, the reactive current is greatly suppressed as compared with the simple projection resonator structure, and a reduction in threshold current and an improvement in laser output are expected. it can.

However, the current confinement structure using the Al oxide layer also has a large problem in terms of heat radiation. Al oxide layer is A
Since the thermal resistance is about five times as large as that of the lAs layer, the heat dissipation of the resonator projections is poor and the temperature during driving is increased. The main heat sources in the surface-emitting type semiconductor laser having the protruding resonator structure are the resistance of the p-type semiconductor multilayer reflective layer,
Alternatively, the heat source is considered to be Joule heat due to the contact resistance between the p-type contact layer and the upper electrode, and these heat sources mainly exist in the resonator protrusion. The current confinement layer is
It must be formed on the resonator projection due to the manufacturing method,
Since the current confinement layer loses its current confinement effect when it is separated from the active layer, it must be formed near the root of the resonator projection. 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. It leads to a rise. As a result, a laser output may not be obtained as expected. In particular, there was a major problem in reliability that is easily affected by heat.

However, when the present invention is applied, the buried metal 212 having good thermal conductivity can be formed in close contact with the periphery of the resonator projection 208, so that the heat generated in the resonator projection 208 can be released to the buried metal 212. As a result, the heat dissipation was dramatically improved, and the device temperature during driving was lowered. As a result, a remarkable increase in laser output and improvement in reliability were obtained.

Therefore, when the present invention is applied to the projecting resonator structure using the Al oxide layer as the current confinement layer, it is possible to achieve both current confinement and heat radiation, which could not be achieved conventionally, and it is extremely effective.

[0060]

As described above, according to the present invention, a metal having a low melting point is used as an embedding material, and it is possible to embed the cavity projection by melting and thereby to embed the material in a very simple manner with good adhesion. As a result, the heat radiation is dramatically improved, the rise in the element temperature during driving can be suppressed, the laser output can be improved, and the reliability can be further improved. It is particularly effective when applied to a surface emitting semiconductor laser having a current confinement layer using an Al oxide layer.

Further, according to the manufacturing method of the present invention, since the buried metal is automatically buried in the cavity projections by melting, the patterning for depositing the buried metal does not require high alignment precision, and is extremely simple. Embedding with high adhesion can be realized. There is no gap between the periphery of the resonator protrusion and the embedded metal. The burrs and the like at the edge portions, which are likely to be generated during patterning, are eliminated by melting, and burying with high flatness can be realized. By using a metal having a relatively low melting point of 400 ° C. or less, there is no need to worry about diffusion of atoms into a semiconductor device, and the device can be manufactured without including a step of deteriorating the device.

[Brief description of the drawings]

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

FIG. 2 is a sectional view illustrating a manufacturing process of the surface emitting semiconductor laser according to the first embodiment of the present invention.

FIG. 3 is a sectional view showing a manufacturing process of the surface emitting semiconductor laser according to the first embodiment of the present invention.

FIG. 4 is a sectional view showing a manufacturing process of the surface emitting semiconductor laser according to the first embodiment of the present invention.

FIG. 5 is a sectional view showing a manufacturing process of the surface emitting semiconductor laser according to the first embodiment of the present invention.

FIG. 6 is a sectional view showing a manufacturing process of the surface emitting semiconductor laser according to the first embodiment of the present invention.

FIG. 7 is a sectional view showing a manufacturing process of the surface emitting semiconductor laser according to the first embodiment of the present invention.

FIG. 8 is a cross-sectional view showing a step of manufacturing the surface-emitting type semiconductor laser according to the first embodiment of the present invention.

FIG. 9 is a sectional view illustrating a manufacturing process of the surface emitting semiconductor laser according to the first embodiment of the present invention.

FIG. 10 is a sectional view showing a surface emitting semiconductor laser according to a second embodiment of the present invention.

[Explanation of symbols]

 101, 201 n-type GaAs substrate 102, 202 n-type semiconductor multilayer reflection layer 103, 203 n-type cladding layer 104, 204 active layer 105, 205 p-type cladding layer 106, 206 p-type semiconductor multilayer reflection layer 107, 207 p-type contact Layers 108, 208 Resonator projections 109, 209 Insulating film 110, 210 Upper electrode 111, 211 Laser emission port 112, 212 Embedded metal 113, 213 Electrode pad 114, 214 Lower electrode 215 Current confinement layer 216 AlAs layer 217 Al oxide layer

Claims (7)

[Claims] 1. A vertical cavity surface emitting semiconductor laser having at least a part of a projecting resonator, wherein an embedding metal having a melting point of 400 ° C. or less is embedded around the projecting resonator. A surface-emitting type semiconductor laser characterized by the above-mentioned. 2. A surface emitting semiconductor laser according to claim 1, wherein said buried metal is an alloy forming a solid solution with gold. 3. A surface emitting semiconductor laser according to claim 1, wherein an electrode pad made of gold is formed on a part of the surface of said buried metal. 4. A method of manufacturing a vertical cavity surface emitting semiconductor laser having a resonator having at least a part of a projection, wherein a step of forming an upper electrode having an opening on an upper surface of the resonator has a melting point. A method for manufacturing a surface-emitting type semiconductor laser, comprising: forming a buried metal of 400 ° C. or less around a resonator projection; and performing a heat treatment at a temperature equal to or higher than the melting point of the buried metal to melt the buried metal. 5. The method of manufacturing a surface emitting semiconductor laser according to claim 4, wherein the step of performing a heat treatment at a temperature equal to or higher than the melting point of the buried metal to melt the buried metal is performed.
A method for manufacturing a surface-emitting type semiconductor laser, which is performed under reduced pressure conditions of 0 Pa or less. 6. The method of manufacturing a surface emitting semiconductor laser according to claim 4, wherein the step of performing a heat treatment at a temperature equal to or higher than the melting point of the buried metal to melt the buried metal is performed.
A method for manufacturing a surface-emitting type semiconductor laser, comprising raising the temperature and melting an embedded metal under a reduced pressure condition of 0 Pa or less, and lowering the temperature under a normal pressure condition in an inert gas atmosphere. 7. A method for manufacturing a surface-emitting type semiconductor laser according to claim 4, wherein the step of heat-treating the buried metal to a temperature equal to or higher than the melting point of the buried metal is performed. A method of manufacturing a surface-emitting type semiconductor laser, comprising: