JPH0837335A - Semiconductor laser and its manufacture - Google Patents

Abstract

PURPOSE:To provide a semiconductor laser which allows less light output saturation by high-bias driving. CONSTITUTION:On an n-InP substrate 101, an n-InP layer 102, an n-InGaAsP layer 115, an active layer 116, a p-InGaAsP layer 117 and a p-InP layer 104 are successively deposited. A mesa strip is formed from the semiconductor multi-layer structure. On the both sides of the stripe, a p-InP layer 105 and an n-InP current block layer 106 are formed, and a buried type heterostructure is formed. An insulating layer 118 is formed on the semiconductor surfaces on the both sides of an electrode 110 by ion implantation by using the electrode 110 as a mask. Then, an SiO2 layer 110 is etched and a metal multi-layer film 112 is deposited on the whole plane. The structure allows heat generated in a laser element to dissipate not only in the contact layer direction, but also in the horizontal direction from the current block layer, when the structure is bonded to a heat sink. Therefore, a semiconductor laser which allows less light output saturation even by high-bias drive is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser having a mesa structure and performing stable transverse mode control, and a manufacturing method.

[0002]

2. Description of the Related Art As a semiconductor laser structure, a buried type hetero structure in which an active layer is covered with a semiconductor material having a large energy gap and a small refractive index is widely used. This embedded heterostructure semiconductor laser is used as a light source for optical fiber communication and optical information processing because it has excellent characteristics such as a low oscillation threshold current value and stable oscillation transverse mode. There is.

A first example of a conventional structure is shown in FIG. This structure consists of n-InP substrate 101, n-InP buffer layer 102, and InGaAs.
After forming a mesa stripe including the P active layer 103 and the p-InP clad layer 104 by etching, the p-InP current blocking layer 105 and n-In are formed by a liquid phase or vapor phase epitaxial growth method.
The P current blocking layer 106 is grown on the side surface of the mesa stripe, and then the p-InP buried layer 107 and the p-InGaAsP contact layer 108 are grown to form a buried hetero structure.

Next, the parasitic capacitance in the current block layer is reduced.
In order to improve the frequency response characteristics, double channel
Dug the entire surface with SiO₂Cover with 109. Next, on the top of the active layer
Mi SiO ₂After removing 109 and forming a p-type electrode 110, a metal multilayer
The film 111 is vapor-deposited on the entire surface. Finally, on the n-InP substrate 101,
Form pole 112. Laser device manufactured by the above process
To improve the heat dissipation characteristics, as shown in Fig. 4,
Soldered to Tosink 113 with junction down
I was there.

A second example of the conventional structure is shown in FIG. This structure consists of n-GaAs substrate 201, n-GaAs buffer layer 202, and n-Al.
GaInP clad layer 203, GaInP active layer 204, first p-AlGaIn
P clad layer 205, second p-AlGaInP clad layer 206, p-Ga
An insulating film mask is formed on the wafer on which the As surface protective layer 207 is laminated, etching is performed up to the second p-AlGaInP clad layer 206 to form a stripe-shaped ridge, and vapor phase epitaxial growth is performed using the mask as a selective mask. Then, an n-GaAs current blocking layer 208 is grown on the side surface of the ridge by the method, and after the insulating film is removed, a p-GaAs buried layer 209 is grown to form a buried structure. Next, the p-GaAs buried layer
A p-type electrode 210 is formed on top of 209, and finally an n-GaAs substrate 201
Then, the n-type electrode 211 is formed. After that, as in the first conventional example, after soldering to the heat sink 113 by junction down, a current was applied to operate.

[0006]

However, in the above structure, an insulating film (SiO ₂ : about 0.08 W / cm · K) having a lower thermal conductivity than InP (thermal conductivity: about 0.6 W / cm · K) is used. Due to the presence of the InGaAsP contact layer (about 0.05 W / cmK), the heat generated between the electrode and the active layer cannot be efficiently dissipated to the heat sink. In addition, the direction of heat radiation is only one direction from the clad layer to the buried layer to the contact layer, so that the efficiency is poor. When the semiconductor laser device has a low heat dissipation characteristic, the saturation of the optical output during high bias driving becomes remarkable.

An object of the present invention is to improve the heat dissipation characteristics of a semiconductor laser device and reduce the optical output saturation during high bias driving.

[0008]

In order to solve the above problems, the present invention provides a current block on both sides of a mesa stripe having a clad layer of a first conductivity type, an active layer, and a clad layer of a second conductivity type. A layer, and a buried layer of a second conductivity type on the mesa stripe and the current blocking layer,
In a buried semiconductor laser structure provided with a second conductivity type contact layer and an electrode metal, regions on both sides of the electrode metal are etched up to the first conductivity type clad layer, and a surface of the region is etched. A semiconductor laser in which insulation is performed and a metal thin film is further formed on the electrode metal and the insulating layer, and a method for manufacturing the same.

Further, it has a first conductivity type clad layer, an active layer, a second conductivity type first clad layer, and a second conductivity type second clad layer having stripe ridges.
In a buried type semiconductor laser structure in which a current blocking layer is provided on both sides of the ridge, and a second conductivity type buried layer and an electrode metal are further provided on the ridge and the current blocking layer, regions on both sides of the electrode metal are provided. Is a semiconductor laser in which the current blocking layer is etched, the surface of the region is insulated, and a metal thin film is formed on the electrode metal and the insulating layer, and a method for manufacturing the same.

[0010]

By the above means, a structure without an insulating film having a low thermal conductivity is provided between the laser element and the heat sink, so that the heat dissipation characteristic can be improved.

Further, since the heat is dissipated laterally from the current blocking layer, the heat dissipation characteristics can be further improved.
Therefore, by the above means, it is possible to obtain good characteristics with little optical output saturation until high bias driving.

[0012]

EXAMPLES Specific examples of the present invention will be described in detail below.

(Embodiment 1) First, a first embodiment will be described.

As shown in FIG. 1A, an n-InP buffer layer 102 having a thickness of 5 μm and an n-InGaA layer having a thickness of 500 nm are formed on an n-InP substrate 101.
sP optical waveguide layer 115, 5 nm thick InGaAsP well layer and 10 nm thick
Multiple quantum well active layer 116 consisting of 5 pairs of InGaAsP barrier layers, p-InGaAsP optical waveguide layer 117 having a thickness of 500 nm, and a thickness of 0.5
From the semiconductor multilayer structure in which the μm p-InP cladding layer 104 was sequentially epitaxially grown, a mesa stripe with a width of about 2 μm was formed by photolithography and etching, and then the p-InP current was applied to the regions on both sides of the mesa stripe by the liquid phase epitaxial growth method. Block layer 105, n-InP current block layer 106
And a p-InP buried layer 107 and a p-InGaAsP contact layer 108 are sequentially grown to form a buried hetero structure.

In FIG. 1B, a SiO ₂ mask 118 having a width of about 20 μm is formed on the p-InGaAsP contact layer 108, and then the n-InP buffer layer 102 is etched with a hydrochloric acid-based etching solution.

In FIG. 1 (c), after removing the SiO ₂ mask 118, a SiO ₂ film 119 having a thickness of 0.15 μm is deposited again, and a groove for electrode formation is opened using a resist mask, and is made of gold, zinc or gold. After sequentially depositing a metal multilayer film, lift off and 350 ° C.
Annealing is performed to form the p-type electrode 110.

The thickness of the SiO ₂ 119 film is 0.15 because it is good enough to allow ions to pass therethrough by ion implantation.
Although the thickness is set to μm, the thickness setting may change depending on the ion and implantation conditions. Further, since the p-type electrode 110 serves as a mask during ion implantation, the p-type electrode 110 needs to have a thickness that does not allow ions to pass therethrough.

In FIG. 1 (d), ion implantation using boron is carried out using the above electrode as a mask so that both sides of the electrode are
After forming an insulating layer 120 on the surface of the semiconductor under SiO ₂ 119, FIG.
The SiO ₂ 119 is etched as shown in (e).

In FIG. 1F, a metal multi-layer film 111 composed of titanium, platinum and gold is vapor-deposited on the entire surface. The reason why titanium is used here is that it has good adhesion to the semiconductor, but there is no problem even if other metals, such as chromium, which have good adhesion, are used. In addition, the reason why platinum is used is to prevent the metal of the solder material from entering the inside of the semiconductor when it is bonded to the heat sink. If this purpose can be satisfied, the type and thickness of the metal can be changed. Is no substitute for getting the same effect. Finally n-InP
N-type electrode 1 made of gold, tin, chromium, platinum, gold on the substrate 101
Forming twelve.

FIG. 2 shows the structure of the laser element manufactured through the above steps after bonding to a heat sink. In the structure of the present invention, unlike the conventional structure, the heat generated in the laser element has high thermal conductivity not only in the direction of the contact layer.
Since heat is also radiated laterally from the InP current blocking layer, it is possible to achieve characteristics with less optical output saturation even at high bias drive.

Although liquid phase epitaxial growth is used for forming the current blocking layer in this embodiment, the same effect can be obtained by using vapor phase epitaxial growth. Although the p-InP current blocking layer and the n-InP current blocking layer were used as the current blocking layer, the current blocking layer is not limited to the InP layer, and the InGaAsP layer has a larger energy gap than the active layer, or semi-insulation. Although boron was used as the material, the same effect can be obtained as long as the ions maintain the insulating property even at the annealing temperature (350 ° C.) during electrode formation. There is no problem even if a transparent InP layer is used.

(Embodiment 2) Next, a second embodiment will be described.

As shown in FIG. 5A, an n-GaAs buffer layer 202 having a thickness of 1 μm and an n-AlGaInP cladding layer 203 having a thickness of 1 μm are formed on an n-GaAs substrate 201 by using a metal organic chemical vapor deposition method. , Thickness 1
Multiple quantum well active layer 212 consisting of 0 nm GaInP layer and 4 nm thick AlGaInP layer, 0.25 μm thick p-AlGaInP cladding layer 205,
6nm thick p-GaInP etching stop layer 213, 0.9μ thick
A p-AlGaInP clad layer 206 of m and a p-GaAs surface protective layer 207 were sequentially epitaxially grown to form a semiconductor multilayer structure, and a SiO ₂ mask having a stripe width of about 4 μm was formed by photolithography and etching, and a sulfuric acid-based etching solution was used. P-
A ridge is formed by etching the AlGaInP cladding layer 206.

At this time, p- for the sulfuric acid type etching solution is used.
The etching rate of the GaInP etching stop layer 213 is
The fact that the p-AlGaInP cladding layer 206 is as slow as one tenth is used. After that, the n-GaAs current blocking layer 208 is stacked by selective growth by metalorganic vapor phase epitaxy using a SiO ₂ mask.
The iO ₂ mask is removed and a p-GaAs burying layer 209 is laminated to form a burying structure.

In FIG. 5B, after SiO ₂ is deposited, a groove for electrode formation is opened using a resist mask, and a metal multilayer film made of chromium and gold is vapor-deposited on the p-GaAs burying layer 209. Then, lift-off is performed to form the p-type electrode 210. Using this electrode as a mask, the n-GaAs current blocking layer 208 is etched with a sulfuric acid-based etching solution. At this time, the side metal is floated in the p-GaAs burying layer 209 under the electrode to float the electrode metal, which causes a short circuit at the time of assembly.
Only the floating electrode portion can be removed by ultrasonic cleaning.

In FIG. 5C, the p-type electrode is used as a resist.
After covering with 214, the semiconductor substrate is attached to the anode, and an electric current is applied in a mixed solution of a tartaric acid aqueous solution and propylene glycol to form an insulating layer 215 made of an oxide of In on both sides of the p-type electrode.

In FIG. 5D, after removing the resist,
A metal multilayer film 216 made of chromium, gold, platinum, and gold is formed on the entire surface. Finally, on the n-GaAs substrate 201, gold, germanium,
After depositing a metal multi-layer film made of nickel, it is annealed at 350 ° C. to form an n-type electrode 211.

The laser device manufactured by the above process is
When the device is operated by bonding it to the heat sink with the junction down as in the case of the above embodiment, it is possible to radiate heat in the direction of the current block layer (lateral direction), so that the optical output saturation can be suppressed even at the time of high bias driving.

In the present invention, the ion implantation or the anodic oxidation method is used for forming the insulating layer, but the same effect can be obtained by using the step of forming the insulating layer on the semiconductor surface in hydrogen peroxide solution.

[0030]

As described in detail above, according to the present invention, the following effects can be obtained.

Since it is possible to dissipate heat to the current block layer without forming an insulating film such as SiO ₂ having a low thermal conductivity in the vicinity of the active layer, the heat generated in the semiconductor can be efficiently generated even during high bias driving. Good characteristics with less light output saturation can be realized.

[Brief description of drawings]

FIG. 1 is a sectional view of a manufacturing process of a semiconductor laser of the present invention.

FIG. 2 is a cross-sectional view after assembling the semiconductor laser of the present invention into a heat sink.

FIG. 3 is a structural sectional view of a conventional semiconductor laser.

FIG. 4 is a cross-sectional view after assembling a semiconductor laser having a conventional structure to a heat sink.

FIG. 5 is a sectional view of a manufacturing process of a semiconductor laser of the present invention.

FIG. 6 is a sectional view showing the structure of a conventional semiconductor laser.

[Explanation of symbols]

101 n-InP substrate 102 n-InP buffer layer 103 InGaAsP active layer 104 p-InP clad layer 105 p-InP current blocking layer 106 n-InP current blocking layer 107 p-InP buried layer 108 p-InGaAsP contact layer 109 SiO ₂ 110 p-type electrode 111 metal multilayer film 112 n-type electrode 113 heat sink 114 solder material 115 n-InGaAsP optical waveguide layer 116 multiple quantum well active layer 117 p-InGaAsP optical waveguide layer 118 SiO ₂ 119 SiO ₂ 120 insulating layer 201 n-GaAs Substrate 202 n-GaAs buffer layer 203 n-AlGaInP clad layer 204 GaInP active layer 205 p-AlGaInP clad layer 206 p-AlGaInP clad layer 207 p-GaAs surface protection layer 208 n-GaAs current blocking layer 209 p-GaAs buried layer 210 p-type electrode 211 n-type electrode 212 multiple quantum well active layer 213 p-GaInP etching stop layer 214 resist 215 insulating layer 216 metal multilayer film

Claims (11)

[Claims] 1. A clad layer of the first conductivity type, an active layer, and a second layer.
A mesa stripe having a conductivity type cladding layer, a current blocking layer provided on both sides of the mesa stripe, and a groove reaching the first conductivity type cladding layer on both sides of the mesa stripe. And a metal thin film provided on the insulating layer and an insulating layer provided on the groove surface. 2. A clad layer of the first conductivity type, an active layer, and a second layer.
A mesa stripe having a conductive type cladding layer, a current blocking layer provided on both sides of the mesa stripe, a second conductive type buried layer and a second conductive type buried layer on the mesa stripe and the current block layer. In a buried semiconductor laser provided with a contact layer and an electrode metal, regions on both sides of the electrode metal are etched up to the first conductivity type clad layer, and a surface of the region is insulated. Furthermore, a semiconductor laser characterized in that a metal thin film is formed on the electrode metal and the insulating layer. 3. A first conductivity type clad layer, an active layer,
A first clad layer of a second conductivity type having a stripe ridge of a second conductivity type; a current blocking layer provided on both sides of the ridge of the first clad layer; and a side of the current blocking layer. A semiconductor laser comprising an insulating layer provided on the surface and a metal thin film provided on the insulating layer. 4. A first conductivity type clad layer, an active layer, a second layer.
And a second clad layer of a second conductive type having a stripe-shaped ridge,
The current block layers are provided on both sides of the ridge of the cladding layer of
Further, in the embedded semiconductor laser structure in which a second conductive type buried layer and an electrode metal are provided on the ridge and the current block layer, regions on both sides of the electrode metal are etched to the current block layer, The surface of the region is insulated, and a metal thin film is formed on the electrode metal and the insulating layer. 5. An etching stop layer is provided between the first cladding layer of the second conductivity type and the second cladding layer of the second conductivity type having a striped ridge. Item 3. A semiconductor laser according to item 3 or 4. 6. A step of forming a first mesa stripe having a first conductivity type clad layer, an active layer, and a second conductivity type clad layer on a first conductivity type substrate, Forming a current blocking layer on both sides of the first mesa stripe; forming a second mesa stripe including the first mesa stripe and having a width wider than the first mesa stripe; A step of forming an electrode metal on the mesa stripe, a step of insulating the surfaces on both sides of the second mesa stripe, and a step of forming a metal thin film on the insulated layer. Manufacturing method of semiconductor laser. 7. A step of forming a first mesa stripe having a first conductive type clad layer, an active layer, and a second conductive type clad layer on a first conductive type substrate, A current blocking layer is formed on both sides of the first mesa stripe, and then a second conductivity type buried layer and a second conductivity type contact layer are sequentially stacked on the first mesa stripe and the current block layer. A step of forming a second mesa stripe including the first mesa stripe and having a width wider than that of the first mesa stripe, and a step of forming an electrode metal on the second mesa stripe, A method of manufacturing a semiconductor laser comprising: a step of insulating the surfaces of regions on both sides of the electrode metal; and a step of forming a metal thin film on the electrode metal and the insulating layer. 8. A first conductivity type clad layer, an active layer, a second conductivity type first clad layer, and a second conductivity type second clad layer on a first conductivity type substrate. Forming a semiconductor multi-layered structure having: and forming a mask on the structure, then etching the second clad layer of the second conductivity type to form a stripe-shaped ridge, Providing a current blocking layer on both sides, further stacking the ridge and a buried layer of a second conductivity type on the current blocking layer, and forming a mesa stripe including the ridge and wider than the ridge. A method of manufacturing a semiconductor laser, comprising: insulating the surfaces of regions on both sides of the mesa stripe having a wide electrode width; and forming a metal thin film on the insulated layer. 9. A first conductivity type clad layer, an active layer, a second conductivity type first clad layer, and a second conductivity type second clad layer on a first conductivity type substrate. Forming a semiconductor multi-layered structure having: and forming a mask on the structure, then etching the second clad layer of the second conductivity type to form a stripe-shaped ridge, Providing a current blocking layer on both sides, further stacking the ridge and a buried layer of a second conductivity type on the current blocking layer, and forming a mesa stripe including the ridge and wider than the ridge. A step of forming an electrode metal on the mesa stripe, a step of insulating the surfaces of regions on both sides of the electrode metal, and a step of forming a metal thin film on the electrode metal and the insulating layer. Characterizing Method for producing a conductor laser. 10. The method of manufacturing a semiconductor laser according to claim 6, wherein the surface of the semiconductor layer is insulated by using ion implantation. 11. The method of manufacturing a semiconductor laser according to claim 6, wherein the surface of the semiconductor layer is insulated by an anodic oxidation method.