JPH05160501A - Surface emitting laser element - Google Patents

Abstract

PURPOSE:To inject carriers into an active layer with low resistance, by forming an electrode on a clad layer formed on an active layer, or forming a conducting layer on the reflector side and a surface. CONSTITUTION:On an N-type reflector composed of N-AlAs 102 and N-GaAs 103, the followings are constituted; an active layer composed of GaAs 116 and an InGaAs quantum well layer 106, an N-clad layer composed of N-AlGaAs 104 and AlGaAs 105, and a P-clad layer composed of AlGaAs 107 and a P<+>- AlGaAs 108. An interface layer 111 having conductivity and an oxide film 112 are formed on the side surface of a P-type reflector composed of P-AlAs 109 and a P-GaAs 110. The whole part of an element is covered with polyimide 113, 114 is an anode and 115 is a cathode. Electrons are injected in the active layer 106 through a substrate 101 and the N-type reflector. Positive holes are injected into the active layer 106 through the P-type reflector and the interface layer 111. Light generated in a quantum well layer 106 is reflected by the p-type reflector and the N-type reflector, and laser oscillation is induced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of a surface emitting laser device.

[0002]

2. Description of the Related Art Up to now, surface emitting laser devices having several types of structures have been proposed. For example, Optronics (19
90), No. 4 pp. 157-175 and Applied Physics Letters vol. 57, No. 16, 1990, pp. 1605-1607 (Appl. Phys.
Lett. 57 (16) 1990). In these structures, the reflector uses a dielectric multilayer film or a semiconductor multilayer film. When the dielectric multilayer film is used for the reflector, a pair such as SiO ₂ 503 and TiO ₂ 504 is used. The active layer is filled with crystals stacked on the substrate. This is shown in FIG. Since the carriers cannot pass through the reflector, there is a problem with the efficiency of injection into the active layer. When using a semiconductor multilayer film for the reflector,
A p-type or n-type impurity is added to the upper and lower reflectors that sandwich the active layer, and carriers are injected into the active layer through these reflectors. The structure may be a mesa shape or an embedded structure.

[0003]

However, the above conventional structure has the following problems. That is, when the dielectric multilayer film is used as a reflector, carriers cannot be directly injected into the active layer through the reflector, so the injection efficiency is lowered and the oscillation threshold is several kA / cm ² , which is the limit for lowering the threshold. There is. Further, when a dielectric multilayer film is formed by a sputtering device or the like, it is difficult to strictly control the film thickness, the thickness deviates from a quarter of the oscillation wavelength, and the reflectance as the theoretical value cannot be obtained. The value becomes high. Further, when the semiconductor multilayer film is used for the reflector, the film thickness can be strictly controlled, but an impurity is added into the reflector and carriers are injected through the reflector. Impurity doping is difficult, and notches or spikes are generated at the interface of the multilayer film, the resistance of the reflector becomes high, and the heat generated after oscillation increases and the element is destroyed. If the amount of impurities added is increased in order to reduce the resistance, there is a problem that the superlattice structure of the multilayer film forming the reflector is destroyed.

Therefore, according to the present invention, carriers are injected into the active layer with a low resistance by forming an electrode on the cladding layer provided on the active layer or forming a conductive layer on the side and surface of the reflector. With the goal.

[0005]

In order to solve this problem, the present invention is a Bragg reflector composed of a semiconductor substrate and a semiconductor multi-layer film deposited on the semiconductor substrate, and has an n-type conductivity. A reflector and n deposited on the n-type reflector
A clad layer, an active layer deposited on the n-clad layer, a p-clad layer deposited on the active layer,
A Bragg reflector composed of a compound semiconductor multilayer film deposited on a clad layer, a p-type reflector having p-type conductivity, and a compound forming the p-type reflector formed on a side surface of the p-type reflector. A semiconductor stoichiometry-shifted layer comprises an oxidized leak layer and an anode deposited on the p-type reflector, or a semiconductor substrate and a semiconductor multilayer deposited on the semiconductor substrate. A Bragg reflector formed of a film, having an n-type conductivity, an n-clad layer deposited on the n-type reflector, an active layer deposited on the n-clad layer, A p-clad layer deposited on the active layer, an upper reflector that is formed of a multilayer film deposited on a partial region of the p-clad layer and causes Bragg reflection, and an upper reflector on the p-clad. Anno deposited on uncoated area And a high-resistivity layer formed immediately below the p-clad layer in the uncoated region of the upper reflector so as to efficiently inject carriers into the active layer with low resistance. ..

[0006]

First, the case where a conductive layer is formed on the side surface of the reflector by an oxidation method using an oxidizing agent will be described. When the reflector is formed by dry etching, lattice defects occur in the crystal on the side surface of the reflector due to collision of charged particles accelerated in a high electric field, and the stoichiometry of the crystal is deviated. Therefore, the oxidation reaction does not proceed according to the theory, the interface between the oxide film and the reflector is not clearly defined, and a leak layer in which the oxide layer and the semiconductor layer are mixed is generated. This leak layer has conductivity because various levels exist in the band. Therefore, holes are injected into the active layer with low resistance.

Next, the case where the electrode is formed on the p-clad will be described. Since the electrode is formed on the p-clad, holes are injected into the active layer with low resistance. There is no resistance problem with electron injection. Further, since the active layer is surrounded by the high resistance layer, carriers are confined inside the active layer.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a sectional view of a surface emitting laser device according to an embodiment of the present invention. A semiconductor multilayer film is epitaxially grown on the n-GaAs substrate 101 by the MBE method or the MOVPE method. n-AlAs102
With a thickness of a quarter of the oscillation wavelength and n-GaAs 103 with a thickness of a quarter of the oscillation wavelength.
Bragg reflection of the lower side is caused by the repeated part,
An n-type reflector composed of n-AlAs 102 and n-GaAs 103 is configured. On top of that, n-AlGaAs1
04 to 100Å ~ 1000Å, AlGaAs105 to 1
00Å ~ 1000Å, GaAs116 100 ~ 200
Å, InGaAs quantum well layer 106 50 Å ~ 100
Å, GaAs116 100-200 Å, AlGaAs
107 to 100Å to 1000Å, p ⁺ -AlGaAs1
08 is grown in this order from 100Å to 1000Å. Thus, the GaAs 116 and the InGaAs quantum well layer 106
Active layer composed of n-AlGaAs104, AlGaA
n-clad layer made of s105, AlGaAs 107,
A p-clad layer made of p ⁺ -AlGaAs 108 is formed. Further, the p-AlAs 109 has a thickness of a quarter of the oscillation wavelength, and the p-GaAs 110 also has a thickness of a quarter of the oscillation wavelength.
The p-type reflector that causes the Bragg reflection on the upper side is formed by repeating the alternating growth with the thickness of 15 times.
An interface layer 111 having conductivity and an oxide film 112 are provided on the side surface of the p-type reflector, and the entire element is covered with polyimide 113. 114 is an anode and 115 is a cathode.

Electrons pass through the substrate 101 and the n-type reflector, and holes pass through the p-type reflector and the interface layer 111, and the active layer 106.
Is injected into. The light generated in the quantum well layer 106 is reflected by the p-type reflector and the n-type reflector to cause laser oscillation. If the anode 114 is processed into a ring shape, laser light is emitted from the surface of the substrate. In the present invention, p
The interface layer 111 having conductivity is provided on the surface of the type reflector, and holes are injected into the active region with low resistance through this layer. The reason why the conductive interface layer 111 is formed is as follows. When performing dry etching,
The collision of charged particles accelerated by the electric field causes lattice defects in the crystal forming the p-type reflector, and the stoichiometry shifts. When oxidized in this state, AlAsO _x , A
_{l 2 O 3, As 2 O} 3, GaAsO x, Ga 2 O 3 and these Al oxides, As, compound composition ratio deviates little Ga and O resulting crystals and oxide film of p-type reflector Various levels are present in the band at the interface with and, and they become conductive.

Therefore, p-AlAs109 and p-GaA
This interface layer 11 without passing through the p-type reflector made of s110
1, carriers are injected into the active region through the p ⁺ -AlGaAs 108. As shown in FIG. 1, a high resistance layer 116 is added to the layers 106, 107 so that the carriers do not diffuse throughout the active layer 106 but are confined within the diameter of the p-type reflector formed above it. It is formed in 116.

FIG. 2 is a process sectional view showing a method of manufacturing the surface-emitting type laser device described above. An anode is formed on a substrate coated with a semiconductor multilayer film (a). Next, dry etching is performed with a mixed gas of chlorine and argon to form a p-type reflector. The condition of dry etching is r
f output is 150W or more, chlorine / argon flow ratio is 1 /
10 to 1/2, internal pressure during reaction is 0.3 to 20 mT
orr. After that, hydrogen is ion-implanted using the resist as a mask. By this ion implantation, the high resistance layer 213 is formed in the n-clad layer (b). The active region and n-type reflector are then formed and the cathode is deposited (c). Next, the active region, the n-type reflector and the substrate are covered with a resist and then boiled in hydrogen peroxide water to form an oxide film on the p-type reflector (d). Finally, after covering the entire device with polyimide, the anode and cathode are exposed (e).

(Embodiment 2) FIG. 3 is a sectional view of a surface emitting laser device according to an embodiment of the present invention. A semiconductor multilayer film is epitaxially grown on the n-GaAs substrate 301 by the MBE method or the MOVPE method. n-AlAs302
With a thickness of 1/4 of the oscillation wavelength and n-GaAs 303 with a thickness of 1/4 of the oscillation wavelength.
N that causes lower Bragg reflection due to repeated parts
A type reflector is constructed. On top of that n-AlGaAs
304 to 100Å to 1000Å, AlGaAs 305 to 100Å to 1000Å, GaAs 307 to 100 to 20
0 Å, InGaAs quantum well layer 306 50 Å ~ 100
Å, GaAs307 to 100-200Å, AlGaAs
308 is 100Å to 1000Å, p ⁺ -AlGaAs3
09 is grown in this order from 100Å to 1000Å. Thus, the GaAs 307 and the InGaAs quantum well layer 306
Active layer composed of n-AlGaAs304, AlGaA
n-clad layer made of s305, AlGaAs 308,
A p-clad layer made of p ⁺ -AlGaAs 309 is formed. Further, p-AlAs 310 has a thickness of a quarter of the oscillation wavelength, and p-GaAs 311 also has a thickness of a quarter of the oscillation wavelength.
The p-type reflector that causes the Bragg reflection on the upper side is formed by repeating the alternating growth with the thickness of 15 times.
Reference numeral 312 is an anode and 313 is a cathode. 314
Is a high resistance layer formed by H ion implantation, and is n-AlG
The aAs 304, AlGaAs 305, InGaAs quantum well layer 306, GaAs 307, and AlGaAs 308 are formed in a ring shape.

Since the anode 312 is formed on the p-clad of the light emitting layer, holes are injected into the active layer with low resistance. Since the high resistance layer is formed from the active layer to the n-clad, the carriers are confined inside this.
Electrons are injected from the cathode 313 through the n-AlGaAs 304 and the n-type reflector into the active layer.

FIG. 4 is a process sectional view showing a method of manufacturing the surface-emitting type laser device described above. The substrate coated with the semiconductor multilayer film is dry-etched with a mixed gas of chlorine and argon to form a p-type reflector 404 and at the same time expose the p ⁺ -AlGaAs layer 403. Subsequently, hydrogen ions are implanted to surround the p-type reflector 404 in the light emitting layer,
The high resistance layer 405 is formed in a ring shape (a). p ⁺ -A
An anode 406 is deposited on the 1GaAs 403 (b), dry etching is again performed with a mixed gas of chlorine and argon to form a light emitting layer, and n-AlGa under the light emitting layer is formed.
Exposing As407. The condition of dry etching is r
f output is 150W or more, chlorine / argon flow ratio is 1 /
10 to 1/2, internal pressure during reaction is 0.3 to 20 mT
orr. Cathode 4 on n-AlGaAs 407
09 is deposited and the process ends (c).

Although hydrogen peroxide solution was used as the oxidizing agent in the first embodiment, it may be a solution prepared by adding metal ions as a catalyst to hydrogen peroxide solution or potassium permanganate. Further, anodic oxidation may be performed using the above solution. At the time of anodic oxidation, a mixed solution of tartaric acid and alcohol or a mixed solution of potassium permanganate and acetone may be used.

Further, in the second embodiment, the semiconductor multilayer film is used for the reflector formed on the light emitting layer, but a dielectric multilayer film may be used.

[0018]

As described above, according to the present invention, a Bragg reflector having a stoichiometrically deviated surface is wet-oxidized to form a conductive layer at the interface between the oxide film and the reflector, or While forming a high resistance layer around the n-clad and the active layer, an electrode is formed on the p ⁺ clad other than the p ⁺ clad and the high resistance layer deposited on the active layer, and the hole is formed from the p ⁺ clad. The electrons are injected from the n-type conductive reflector. As a result, in a surface-emitting laser device that employs a Bragg reflector that uses a semiconductor multilayer film, carriers can be injected into the active layer with low resistance, which reduces the oscillation threshold and the amount of heat generated by reducing the operating voltage. The effect is obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a surface-emission type laser device configured by using an oxide film.

2A to 2C are cross-sectional views of a process of manufacturing a surface-emission type laser device configured by using an oxide film.

FIG. 3 is a cross-sectional view of a surface emitting laser device in which electrodes are deposited on the p ⁺ clad and the n clad, and a high resistance layer is provided.

FIG. 4 is a process cross-sectional view of a process for manufacturing a surface emitting laser device in which electrodes are deposited on the p ⁺ clad and the n clad, and a high resistance layer is provided.

FIG. 5 is a sectional view of a process of a surface emitting laser device.

[Explanation of symbols]

101 n-GaAs substrate 102 n-AlAs 103 n-GaAs 104 n-AlGaAs 105 AlGaAs 106 InGaAs 107 AlGaAs 108 p ⁺ -AlGaAs 109 p-AlAs 110 p-GaAs 111 Interface layer 112 Oxide film 113 Polyimide 114 Anode 115 Cathode 116 GaAs 201 n-GaAs substrate 202 Semiconductor multilayer film 203 Anode 204 Resist 205 p Mirror 206 Light emitting layer and n mirror 207 Resist 208 Cathode 209 Resist 210 Interface layer 211 Oxide film 212 Polyimide 301 n-GaAs substrate 302 n-AlAs 303 n-GaAs 304 n-AlGaAs 305 AlGaAs 306 InGaAs 307 GaAs 308 AlGaAs 309 p ⁺ -AlGaAs 310 p-AlAs 311 p-GaAs 312 anode 313 cathode 314 high resistance layer 401 n-GaAs substrate 402 semiconductor multilayer film 403 p ⁺ -AlGaAs 404 p mirror 405 high resistance layer 406 anode 407 n-AlGaAs 408 n mirror 409 Cathode

Claims (2)

[Claims] 1. A Bragg reflector composed of a semiconductor substrate, a semiconductor multilayer film deposited on the semiconductor substrate, an n-type reflector having n-type conductivity, and a Bragg reflector deposited on the n-type reflector. n
A clad layer, an active layer deposited on the n-clad layer, a p-clad layer deposited on the active layer,
A Bragg reflector composed of a compound semiconductor multilayer film deposited on a clad layer, a p-type reflector having p-type conductivity, and a compound forming the p-type reflector formed on a side surface of the p-type reflector. A surface emitting laser device comprising: a leak layer in which a stoichiometric layer of semiconductor is oxidized; and an anode deposited on the p-type reflector. 2. A Bragg reflector composed of a semiconductor substrate, a semiconductor multilayer film deposited on the semiconductor substrate, an n-type reflector having n-type conductivity, and a n-type reflector deposited on the n-type reflector. n
A clad layer, an active layer deposited on the n-clad layer, a p-clad layer deposited on the active layer,
An upper reflector formed of a multi-layered film deposited on a partial region of the clad layer to cause Bragg reflection; an anode deposited on an uncoated region of the upper reflector on the p-clad; A surface emitting laser device comprising: a high resistance layer formed immediately below the p-clad layer in a region where the upper reflector is not adhered.