JPS62296584A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To decrease the energy gap of an active layer in a region in a laser, to remove light absorption at an end surface section and to enable laser oscillation having long life by selectively increasing an impurity in a layer separated from the active layer only by one layer and partially doping the impurity to the active layer during crystal growth. CONSTITUTION:An N GaAs layer 2 is grown on a P-type GaAs substrate 1 through liquid phase epitaxial growth, a region within 30mum from sections as resonator end-surfaces is coated with an Si3N4 film 9, Zn is implanted through ion implantation, a groove 8 is formed through etching, and the nose of the groove is intruded into the substrate 1. A P-GaAlAs layer 3, a GaAlAs layer 4, an N-GaAlAs layer 5 and an N-GaAs layer 6 are grown in succession through liquid growth again. Zn implanted to the layer 2 enters the layers 3, 4 by a diffusion at that time. An AuGeNi electrode 11 is evaporated and alloyed on the layer 6 side and an AuZn electrode 10 on the substrate side.

Description

DETAILED DESCRIPTION OF THE INVENTION 3. Detailed Description of the Invention Field of Industrial Application The present invention relates to a semiconductor laser device used in optical information processing equipment and the like that utilizes laser beams.

BACKGROUND OF THE INVENTION Because semiconductor devices are small and lightweight, they are very important as components of optical disc pickups, and the demand for them has been increasing in recent years.

By the way, since optical disks have a higher recording density than magnetic disks, they are being used as large-capacity digital memories in computer storage devices. In this case, since information is recorded on the optical disk using heat generated when the semiconductor laser beam is focused, the demand for high-speed recording inevitably requires an increase in the optical output of the semiconductor laser beam.

Problems to be Solved by the Invention Although the optical output of semiconductor lasers has been achieved in the 4o to somW class by optimizing the device structure, there is a problem in practical use that the lifetime is short in continuous operation. A factor that shortens the life of a semiconductor laser is damage to the resonator end face due to excessive optical output. Since the laser light density is high in the crystal near the resonator end face, the temperature rises due to the absorption of light at the end face, causing oxidation and melting of the crystal.

In a three-page semiconductor laser, in order to prevent the end facets from being damaged by light, it is preferable to prevent the laser light from being absorbed within the crystal near the end facets. That is, it is better to increase the energy gap of the semiconductor crystal near the end face, or conversely to decrease the energy gap in the internal region. In this way, absorption of the laser beam at the end face portion can be eliminated.

Means for solving the problem In the Ga A QA s semiconductor laser, the active layer that causes laser oscillation is made of a Ga A (2A s mixed crystal), and its energy gap is determined by the Ae mixed crystal ratio. .

Therefore, it is only necessary to change the Al mixed crystal ratio near the end face and inside. However, it is generally difficult to fabricate such a structure.

Another way to change the energy gear knob is by doping with impurities. That is, doping with impurities at a high concentration reduces the energy gear knob. Therefore, it is preferable to introduce impurities at a high concentration only in the region inside the laser. Although this is generally difficult, it is possible by using diffusion of p-type impurities.

In the present invention, impurities are selectively added to a layer one space apart from the active layer, and the active layer is partially doped by diffusion of impurities during crystal growth of the active layer.
The energy gap of the active layer inside the laser is reduced to eliminate light absorption at the end facets.

The optical density is high at the end face of the laser resonator, but since the energy gear knob is large relative to the laser beam at the oscillation wavelength, absorption of the laser light does not occur at the end face, and therefore heat generation is suppressed. There is no deterioration (oxidation or melting) of the laser, and long-life laser oscillation is possible.

Embodiment FIG. 1 shows a structural diagram of a semiconductor device in an embodiment of the present invention. Fig. 1a shows the structure of the end face, and Fig. 1b shows the internal structure. That is, in FIG. 1C, BB'
FIG. FIG. 1C on page 5 is a structural diagram of FIG. 1A divided along A=A' so that the inside can be seen. The features of this semiconductor laser are that the soil part of the n-GaAs layer 2 in the laser and the p-
The GaAlAs layer 3 and the GaAlAs layer 4 have a highly Zn-doped region 7. Laser oscillation is caused by the groove 8.
This occurs in the upper layer 4, but in the vicinity of the resonator end face 30
Since the Zn concentration is low and the energy gap is large in the μm region, laser light is not absorbed. In this way, ion implantation and thermal diffusion are used to partially increase the Zn concentration inside the laser.

The manufacturing process will be explained step by step with reference to FIG.

(a) An n GaAs layer 2 is grown on a p-type Ga AB substrate 1 by liquid phase epitaxial growth. The film thickness is 1.3 μm.

(b) A region within 30 μm from the part that will become the cavity end face is covered with a Si3N4 film, and Zn is added to it by ion implantation.
×10 (7) Inject. The implantation depth is 0.31 tm.

(c) Create groove 8 by etching. The depth of the groove is 1.5
The thickness is 6 μm, and the tip is made to penetrate into the substrate 1.

(d) Grow each layer from 3 to 6 at 860° C. again by liquid phase growth. At this time, the Zn implanted into layer 2 diffuses into layers 3 and 4.

(e) AuGeNi electrode 11 is deposited on the layer 6 side, and AuZn electrode 1o is deposited on the substrate side to complete the process.

FIG. 3 shows the current-light output characteristics of the laser of the present invention. For comparison, a device with the same structure but without Zn implantation is also shown. The level of destruction of the element was significantly improved, and it can be seen that the effect of eliminating absorption at the end face is significant. Figure 4 shows the results of the high temperature current test. It can be seen that the lifespan is greatly extended and the reliability is significantly improved compared to the one without injection.

Effects of the Invention According to the present invention, the reliability of a high-output semiconductor laser can be raised to a practical level by 1, which has a great effect in applications such as optical disks.

[Brief explanation of the drawing]

Fig. 1 is a structural diagram of the semiconductor laser of the present invention, Fig. 27 is a perspective view showing the manufacturing process, Fig. 3 is a characteristic diagram showing current-light output characteristics, and Fig. 4 is the result of a high-temperature current life test. FIG. 1----p-GaAs substrate, 2-=-n-GaA
s layer, 3...-p-GaAlAs layer, 4--- Ga
AlAs layer, 5 .---n-GaAlAs layer, 6...
... n-GaAs layer, 7... Highly Zn doped region, 8... Groove, 9... Ion implantation region, 1o
...AuZn electrode, 11...AuGeNi
electrode. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure f-P-GaAaha2--n-G
a, As q-11ifu)

Claims (1)

[Claims] There is a GaAs layer of a conductivity type opposite to the one conductivity type on a GaAs substrate of one conductivity type, a groove reaching the substrate is provided in the GaAs layer of the opposite conductivity type, and a double hetero p-
It has an n-junction and is 5 μm from the cavity end face of the element.
In a region within 50 μm from
The impurity of the one conductivity type is contained in the upper part of the layer, the GaAlAs layer of the one conductivity type, and the GaAlAs active layer above the layer, than the end face of the resonator in the same layer. Semiconductor laser equipment.