JPH0740619B2 - Semiconductor laser device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface emitting semiconductor laser device which is easy to manufacture and has good characteristics.

2. Description of the Related Art Surface-emitting type semiconductor laser devices can be monolithically formed into a two-dimensional array or integrated by stacking, and new applications are expected in the fields of optical information processing and optical electronics.

Conventionally, a structure shown in FIG. 4 has been proposed as an example of this type of semiconductor laser device (Proceedings of the 32nd Joint Lecture on Applied Physics 31a-ZB-2). In FIG. 4, 1 is an electrode, 2 is an N-type InP substrate, 3 is an N-type InGaAsP layer, and 4 is an N-type InP substrate.
P layer, 5 is P type InP layer, 6 is P type InGaAsP layer, 7 is an electrode,
Reference numeral 8 is a non-doped InGaAsP active layer, 9 is a SiO ₂ insulating film, 10 and 11 are thin metal reflective films, 12 is a polyimide resin, and 13 and 13 'are laser emission lights. When a current is applied between the electrodes 7 and 8, holes are injected from the p-type InP layer 5 and electrons are injected into the InGaAsP active layer 6 from the N-type InP layer 4 layer to emit light. This light is reflected between the reflection films 10 and 11 to cause laser oscillation.

Problems to be Solved by the Invention In the structure of the conventional laser device described above, a current is effectively injected into a part of the InGaAsP active layer 8 after being processed into a mesa shape, and then embedded with an insulating polyimide resin to form a surface. Since it is flattened, it is difficult to increase the yield of the device by requiring a complicated process in manufacturing. Further, since the InGaAsP active layer 8 is exposed to the outside by etching, there is a problem that non-radiative recombination centers are formed on the surface. Further, if the light emitting region is made small, there is a problem that the electrode contact area of the mesa portion becomes small and the contact resistance becomes high. Further, since the polyimide resin has a low thermal conductivity, the heat dissipation effect of the device is hindered, and continuous oscillation operation is difficult.

The present invention has been made in view of the above points, and provides a semiconductor laser device which is easy to manufacture and has good characteristics.

Means for Solving the Problems The present invention relates to a first conductive type multi-quantum well active region and a second conductive type clad, which are made of an ultrathin film having a carrier de Broglie wavelength or less on a compound semiconductor substrate. Layers,
A second conductive type impurity is diffused in high concentration from the surface side of the clad layer to the peripheral part except the laser emitting part to disorder the multi-quantum well structure in the lower part, so that a current flows in the active region in the planar structure. The above-mentioned problems are solved by injecting effectively.

Further, by alternately laminating two crystal layers having different compositions in the compound semiconductor substrate, each having a thickness of about 1/2 times or 1 times the wavelength of the laser light in the layer, the reflection portion on the back surface of the substrate is unnecessary and the wavelength is reduced. It has selectivity.

Action The present invention has the above-described structure, and by utilizing the effect that the multiple quantum well structure is disordered by high-concentration impurity diffusion and the equivalent absorption edge shifts to the short wavelength side, it is possible to inject carriers into only a predetermined active region in the planar structure. I have to. Further, by completely laminating two types of crystal layers having different compositions to form a refractive index modulation type diffraction grating to form a distributed reflector, a complete planar structure can be obtained.

Embodiment FIG. 1 is a sectional structural view of an embodiment of the present invention. In the following drawings, the same parts in FIG. In FIG. 1, 101 is an active layer having a multi-quantum well (MQW) structure, 102 is a high-concentration P-type impurity diffusion region, and 103 is a disordered MQW layer. An enlarged view of the multiple quantum well structure active layer 101 is shown in FIG. In FIG. 2, 104 is an N-type InP barrier layer and 105 is an N-type InGaAsP well layer, and two types of layers are alternately and periodically laminated to form a multiple quantum well structure.

The element manufacturing procedure is as follows. First, the liquid crystal epitaxial method (LPE method), which is a conventional crystal growth technique, is used to form the N-type InGaAsP layer 3 (up to 0.5 μm thick) and the N-type InP layer 4 (up to 0.5 μm) on the N-type InP substrate 2. 5
μm thick), a non-doped N-type InP barrier layer (up to 300 Å thickness) and a non-doped N-type InGaAsP well layer (up to 150 Å thickness), each of which has a periodic structure of 10 layers, and the multiple quantum well structure active layer 101, P-type I
nP layer 5 (up to 2 μm thick), P-type InGaAsP layer 6 (up to 0.5 μm)
(Thickness) is continued to grow crystals. Next, on the P-type InGaAsP layer 6, a silicon nitride film (~
0.1 μm thick) and silicon oxide film by CVD method (up to 0.2 μm)
Thickness).

Next, the peripheral silicon nitride film and silicon oxide film except for the circular laser emitting part with a radius of 10 μm are removed by ordinary photolithography and etching techniques, and then ZnP ₂ and ZnAs ₂ are used as diffusion sources. High-concentration P-type impurity diffusion region 10 for thermal diffusion of Zn (600 ℃, 30min) by phase
Form 2. At this time, impurities were diffused. The MQW layer 101 becomes a disordered MQW layer 103, and the band gap is sufficiently larger than the lowest quantum level energy of the MQW layer 101 due to the effect of homogenizing the composition. It becomes transparent. Next, a P-type ohmic electrode (An / Zn) is vapor-deposited on the region where Zn is thermally diffused. Next, an N-type ohmic electrode (Au / Sn) is vapor-deposited on the back surface side of the N-type InP substrate, followed by sintering treatment (400 ° C., 10 min). Patterning is performed on the back surface of the laser emitting portion, and holes are opened with a hydrochloric acid-based etching solution. Since the etching rate of hydrochloric acid-based etchant is high for InP, but slow for InGaAsP layer 3,
Only nP can be easily etched. Next, a thin film of An (up to 400 Å) is vapor-deposited on the front and back surfaces to form the reflective films 10 and 11.

The operating principle of the device is that a current is passed from the electrode 7 to the electrode 1 so that the p-InP layer 5 and the high-concentration P-type impurity diffusion region 1 are formed.
Holes from 02 and electrons from the N-InP layer 4 are MQW, respectively.
It is injected into the layer 101 and recombines to emit light. This light is reflected film 1
It resonates between 0 and 11 and oscillates to generate laser oscillation light 13 and 13 'to the outside.

In this structure, since it is not necessary to perform complicated etching on the surface side of the substrate, the yield is improved, and surface recombination can be reduced because the active layer is not exposed. Further, the contact area of the P-type electrode is set to the high-concentration P-type impurity diffusion region 102.
The contact resistance can be reduced because it can be widely formed. Further, since the heat dissipation characteristic is better than that of the embodiment, continuous operation laser oscillation at room temperature can be obtained.

Next, a second embodiment of the present invention will be described using the sectional structure shown in FIG. In FIG. 2, reference numeral 106 denotes a distributed reflection region having a periodic structure of the InP low refractive index layer 107 and the InGaAsP high refractive index layer 108. InP low refractive index layer 107 and InGaAsP high refractive index layer 108
Since they have different refractive indexes, they act as a refractive index modulation type diffraction grating. The thickness d of each layer is the wavelength λ of the laser light.
And the refractive index n for this wavelength can be expressed as follows.

The larger the number of periodic structures, the better, but it can be selected appropriately and an effect can be obtained even with about 20 periods.

In this structure, the light emission of the MQW layer is the same as that in the previous embodiment, and the laser oscillation occurs when light is reflected between the reflective film 10 and the distributed Bragg reflector region 106. At this time, the wavelength of light oscillates at only a single wavelength due to the influence of the wavelength dependence of the reflectance of the distributed Bragg reflector region. Since this structure is completely planarized, it is possible to increase the yield and obtain a semiconductor laser that operates at a low threshold current and has uniform characteristics.

Note that the compound semiconductor substrate as one component in the present invention refers to a portion below the multiple quantum well structure active layer and is different from the substrate before crystal growth.

In the above two embodiments, the element having the oscillation wavelength in the infrared using the InP and InGaAsP crystals has been described, but the present invention can be applied not only to the GaAs and GaAlAs type crystals but also to other compound semiconductor crystal materials. The same effect can be obtained with respect to. In the element structure, the reflection films 10 and 11 are
However, the thickness can be selected without the reflective film. In the embodiment of the present invention, N
Although the example using the type substrate is shown, it goes without saying that the same effect can be obtained by using the P type or semi-insulating substrate.

EFFECTS OF THE INVENTION According to the present invention, it is possible to obtain good characteristics such as a semiconductor laser device with a high yield and low threshold current and high efficiency, which is of great significance in industry. Further, this semiconductor laser device can be easily formed into a monolithic two-dimensional array, which greatly contributes to new applications in the fields of optical information processing and optical electronics.

[Brief description of drawings]

1 is a sectional view of a surface emitting semiconductor laser device according to an embodiment of the present invention, FIG. 2 is an enlarged sectional view of a main part of the device, and FIG. 3 is a surface emitting device of another embodiment of the present invention. Type semiconductor laser device, and FIG. 4 is a sectional view of a conventional surface-emitting type semiconductor laser device. 101 ... Multiple quantum well structure active layer (MQW layer), 102 ... High-concentration P-type impurity diffusion region, 103 ... Disordered multiple quantum well structure active layer, 104 ... Barrier layer, 105 ... Well layer, 106 ... Distributed reflection region, 107 ... Low refractive index layer, 108 ...
… High refractive index layer.

Claims (1)

[Claims] 1. A crystal semiconductor layer having a thickness equal to or less than a de Broglie wavelength of a carrier is formed on a substantially flat substrate of a compound semiconductor, and each of the crystal layers has a thickness about 1/2 or 1 times the laser wavelength in the layer. A multi-quantum well structure of the first conductivity type and a cladding layer of the second conductivity type, which are alternately laminated each other, are provided, and the second conductivity type is provided in the peripheral portion except the laser emitting portion from the flat surface side of the clad layer. Surface-emitting type semiconductor laser device in which the multi-quantum well structure below is disordered by diffusing high-concentration impurities of high type.