JPH0227829B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing an internal stripe type semiconductor laser device.

As a prior art, an internal stripe type semiconductor laser device having a structure as shown in FIG. 1 and a method for manufacturing the same have been proposed. In this internal stripe type semiconductor laser device, a confinement layer 6 made of n-GaAs is formed on the p-GaAs substrate 5;
p-Ga _1-y Al _y
A clad layer 1 made of As, an active layer 2 made of n-Ga _1-x Al _x As, a clad layer 3 made of n-Ga _1-y Al _y As, and a cap layer 4 made of n-GaAs are arranged in this order. It is formed. However, 0<x<y<1
It is. Further, a p-type electrode 9 is formed on the lower surface of the substrate 5, and an n-type electrode 8 is formed on the upper surface of the cap layer 4.

However, in a semiconductor laser device having such a structure, the entire device emits light, and it is not possible to realize laser light emission only from the stripe grooves 7.
The reason for this will be explained with reference to FIG. Here, FIG. 2a shows the energy band inside the stripe groove 7, and FIG. 2b shows the energy band outside the stripe groove 7. The cladding layer 1 and the substrate 5 in the stripe groove 7 are both p
type, and almost no voltage is applied. Therefore, no voltage is applied to the cladding layer 1, the confinement layer 6, and the substrate 5 outside the stripe groove 7.
It remains in equilibrium.

As shown by the wavy arrow, it occurs in the active layer 2, and hν
(where h: Planck's constant, ν: frequency) After passing through the cladding layer 1, which has an energy gap Eg1 larger than hν, the light has a stripe with an energy gap Eg2 smaller than hν. It is absorbed in the confinement layer 6 near the groove 7, thereby generating electron-hole pairs. still,
Electrons are shown as black circles, and holes are shown as white circles. As a result, electrons are accumulated in the confinement layer 6, and holes are accumulated in the cladding layer 1, which turns on and becomes conductive. When the vicinity of the stripe groove 7 becomes conductive and the active layer 2 begins to emit light, the light causes the conductive region to expand. Such a process is repeated until the entire element becomes conductive, so that laser oscillation is not realized only within the striped grooves 7.

That is, in the prior art shown in FIGS. 1 and 2, before the light having energy hν is incident,
Although the current path width is the width W3 of the striped groove 7, when the light having the energy hν enters the confinement layer 6, the reverse bias polarity junction interface between the cladding layer 1 and the confinement layer 6 is turned on, i.e. The conduction and current path width is the width W3 of the stripe groove 7 and the turned-on width △W4, △W5
(i.e. W3 + △W4 + △W5) and becomes wider. Therefore, the current confinement effect disappears.
Therefore, the current density decreases and oscillation stops.

In order to solve the above-mentioned problems,
As shown in Japanese Patent No. 125690, there is a CSP type laser having a light guide layer, but this structure cannot completely solve the problem. Therefore, for this CSP laser,
52-90280, a reverse conductivity type layer is provided on the substrate side for current confinement, and JP-A-51-58879
Although it is relatively easy to think of providing a reverse conductivity type layer in the cladding layer for current confinement, an effective manufacturing method for this purpose has not yet been found.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned technical problems and provide a method for manufacturing an internal stripe type semiconductor laser device in which a current is reliably confined within the stripe groove and laser oscillation occurs.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is a cross-sectional view of an internal stripe type semiconductor device manufactured according to an embodiment of the present invention.

First, ^{a Te}
A confinement layer 37 made of n-GaAs doped with, for example, about 1×10 ¹⁸ /cm ³ is uniformly grown to a thickness of about 1 μm. Width W1 for this wafer
Striped grooves having a diameter of 6 μm and a depth of 1.2 μm are formed at a pitch of, for example, 300 μm by a well-known photoetching technique. Then, by a liquid phase epitaxial method using a sliding boat, Si was doped onto the wafer at a concentration of 1×10 ¹⁷ /cm ³ .
- Cladding layer 31 made of Ga _0.5 Al _0.5 As and p-Ga _0.7 doped with Ge at a concentration of 3×10 ¹⁷ /cm ³
A light guide layer 32 made of Al _0.3 As and 1× Si
n-Ga _0.83 Al _0.17 doped at a concentration of 10 ¹⁷ /cm ³
An active layer 33 made of As, a cladding layer 34 made of n-Ga _0.5 Al _0.5 As doped with Te at a concentration of 1× ¹⁰ 18 /cm ³ , and a cladding layer 34 doped with Te at a concentration of 5×10 ¹⁸ /cm ³ . Cap layer 3 made of n-GaAs
5 and are grown successively in this order. Thereafter, the substrate is kept at a temperature of about 790°C for about 40 minutes in the same growth furnace to diffuse Zn in the substrate 36 and form the cladding layer 3.
By converting the n-Ga _0.5 Al _0.5 As in No. 1 to p-type, a current path is formed in the stripe groove 38. Then, Au-Ge-Ni is deposited on the surface of the growth layer, and Au-Zn is deposited on the surface of the substrate 37 to form an alloy, thereby forming an n-type electrode 39 and a p-type electrode 40.

By cleaving the wafer thus formed at right angles to the stripe grooves 38,
Form a 250μm resonator.

The semiconductor laser device formed through these processes had a threshold value of 40 mA and an oscillation wavelength of 760 μm. Moreover, the laser did not break down even at a laser output of 50 mW.

This internal stripe type semiconductor laser element is
Substrate 36 made of p-GaAs doped with Zn
On top, a confinement layer 37 made of n-GaAs, n-
Clad layer 31 consisting of Ga _1-y Al _y As, p-Ga _1-z
Optical guide layer 32 made of Al _z As, n-Ga _1-x Al _x
An active layer 33 made of As, a cladding layer 34 made of n-Ga _1-y Al _y As, and a cap layer 35 made of n-GaAs are formed in this order, and 0<x<z
<y<1 is satisfied.

The stripe grooves 38 are formed by heat-treating the crystal to diffuse Zn atoms in the substrate 36 and forming the n-type cladding layer 31.
It is formed by converting a part of Zn to p-type, but the diffusion rate of Zn atoms in GaAlAs system is
The smaller the Al ratio, the slower the Zn atoms diffuse into the cladding layer 31.
The light guide layer 32, which has a small ratio, substantially stops that diffusion. Furthermore, since the diffusion rate of Zn atoms in the confinement layer 37 is extremely slow, the diffusion of Zn into the confinement layer 37 can be ignored. That is,
The confinement layer 37 has a function of preventing Zn atoms from diffusing into the cladding layer 31 in areas other than the stripe grooves 38.

The operation of the internal stripe type semiconductor laser device constructed by such a manufacturing method will be explained with reference to FIG. In addition, Fig. 4a shows the stripe groove 3.
8, and FIG. 4b is an energy band diagram in a region outside the stripe groove 38. FIG. Light generated in the active layer 33 in the portion corresponding to the stripe groove 38 and having an energy of hν has an energy gap larger than hν.
After passing through the optical guide layer 32 and cladding layer 31 having Eg3 and Eg4, the light is absorbed by the confinement layer 37 near the stripe groove 38, which has an energy gap Eg5 smaller than hv. Electron-hole pairs are thereby generated.

Here, as is clear from FIG. 4b, the holes generated in the confinement layer 37 cannot cross the high barrier of the cladding layer 31, and therefore cannot be turned on. Therefore, the current is width
Since it is allowed to flow only within the stripe groove 38 having W1, an internal stripe type semiconductor laser device with a low threshold value is realized. Furthermore, since the optical guide layer 32 is provided, a high-output semiconductor laser device can be realized at the same time.

FIG. 5 shows the structure of another semiconductor laser device manufactured by the manufacturing method of the present invention, and parts corresponding to the embodiment of FIG. 3 are given the same reference numerals. In this embodiment, the cladding layer 51 made of n-Ga _1-y Al _y As is curved within the stripe groove 58 and has a p-
It is closest to the substrate 36 made of GaAs. Therefore, the area in which Zn is diffused only needs to be small, and therefore the current injection width W2 can be narrowed.
Furthermore, if the optical guide layer 52 and the active layer 53 are curved as shown in the figure, the laser beam can be confined within the stripe groove 58 due to the difference in effective refractive index, resulting in a single mode and a low threshold. can be realized.

According to the results of experiments conducted using a semiconductor laser device as shown in FIG. 5, it was possible to achieve an oscillation threshold of 20 mA at an oscillation wavelength of 760 nm. Furthermore, both the transverse mode and the longitudinal mode were single, and there was no damage up to a laser output of 50mW.

According to the invention, the cladding layer 3 has an energy gap Eg4 larger than the energy hν.
1 and 51 are interposed between the confinement layer 37 and the reverse bias polarity junction interface to form the optical confinement layer 37.
This prevents it from turning on when the light is incident on it. The reverse bias polarity junction interface here refers to the cladding layers 31 and 51 and the optical guide layer 3.
Refers to the pn junction surface with 2,52.

The present invention is not limited to the double heterostructure as in the embodiments described above, but can be implemented in connection with a single heterostructure or multi-heterostructure semiconductor laser device.

As described above, according to the present invention, the cladding layer is of p-type conductivity within the stripe grooves formed in the element, and is of n-type conductivity outside the stripe grooves.
The clad layer of type conductivity type and the light guide layer of p type conductivity form a p-n junction, and the energy gap Eg4 between the clad layers 31 and 51 is
is made larger than the energy hν of the generated laser light, so the current flows through the stripe grooves 38, 58.
Therefore, even if the laser light enters the confinement layer 37, it is prevented from being turned on.

Furthermore, after forming the n-type GaAs confinement layer, a striped groove reaching the p-type substrate is formed, and then the n-type GaAs confinement layer is formed.
By sequentially epitaxially growing a GaAlAs cladding layer, a p-type optical guide layer, etc., and forming a current path by diffusion from the substrate to the optical guiding layer, it is possible to eliminate the step of exposing the GaAlAs layer.
It becomes possible to form an internal stripe type semiconductor laser device with a GaAlAs cladding layer.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an internal stripe type semiconductor laser device of the prior art, FIGS. 2a and b are energy band diagrams of the internal stripe type semiconductor laser device of FIG. 4a and 4b are energy band diagrams of the internal stripe type semiconductor laser device of FIG. 3, and FIG. 5 is a sectional view of the internal stripe type semiconductor laser device according to the present invention. . 31, 51... Cladding layer, 32, 52... Light guide layer, 36... Substrate, 38, 58... Internal stripe groove.

Claims (1)

[Claims] 1. An n-type GaAs confinement layer 37 is superimposed on a p-type GaAs substrate 36, and striped grooves 38, 58 are formed to penetrate through the confinement layer 37 and reach the substrate 36.
and forming n-type GaAlAs cladding layers 31, 51, p-type optical guide layers 32, 52, and laser oscillation active layers 33, 53 on the grooves 38, 58 and the confinement layer 37. a step of stacking a laser oscillation operating section sandwiched at a heterojunction interface; and a cladding layer region located between the grooves 38, 58 and the laser oscillation operating section directly above the grooves 38, 58. 31, 51, p-type impurities are diffused from the substrate 36 to form optical guide layers 32, 52.
A method of manufacturing a semiconductor laser device, comprising the steps of: forming a p-type conversion region reaching 100 nm, and a current path is opened by the p-type conversion region of the striped grooves 38 and 58.