JPH03280482A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To enable a semiconductor laser to oscillate continuously at a high ambient temperature, be manufactured excellent in reproducibility, and stably output laser rays by a method wherein Zn is added to a P-type clad layer as an acceptor, Mg is added to a first layer provided onto an active layer, and a second layer is provided onto the first layer. CONSTITUTION:The following are provided: an N-type GaAs substrate 1; an N-type GaInP buffer layer 2 0.5mum in thickness; an N-type Al GaInP clad layer 3 doped with Se as a donor and 1.2mum in thickness; an undoped GaInP active layer 4 0.8mum in thickness; a P-type Al GaInO first clad layer 5 doped with Zn as a acceptor and 0.07mum in thickness; a P-type second clad layer 6 doped with Mg as an acceptor and 1.1mum in thickness; and a P-type GaInP contact layer 7. By this setup, an excellent interface of small defect can be formed between the active layer 4 and the P-type first clad layer 5.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to an AlGa1nP semiconductor laser that emits visible light.

(b) Prior Art AjGaInP has a wavelength in the 0.6 μm band and is used as a material for visible light semiconductor lasers.

FIG. 4 shows a conventional AjGaInP semiconductor laser, which is described in, for example, Japanese Patent Laid-Open No. 62-200786.

In the figure, (20) is a substrate made of n-type GaAs, (
21) is a buffer layer made of n-type GaInP, (22)
is an n-type cladding layer made of n-type AjGaInP, (23
) is an active layer made of undoped Ga1nP, (24)
is an n-type cladding layer made of p-type AjGalnP.

These layers are deposited on the substrate (20) using the well-known MOCVD method.
are sequentially epitaxially grown on the main surface of. Also, n
The mold cladding layer (24) has a width of 5 μm by etching.
A striped ridge (25) is formed.

(26) N-type cladding layer excluding the top of the beam (25) (
24) A block layer made of n-type GaAs epitaxially grown on top of the block layer, (27) an exposed n-type cladding layer (
24) is a cap layer made of p-type GaAs epitaxially grown on the top of the ridge (25) and the block layer (26), (28) is a p-side electrode formed on the cap layer (27), and (29) is the substrate. (20) is an nQll electrode formed on the other main surface.

Mg and Zn are used as p-type impurities in such A(GaInP-based semiconductor lasers).

However, in Zn, (A go, IcaO, s) o, s I no,
In sP, a carrier concentration of only about 3 to 4 x 10 "cm-" can be obtained, and a sufficient heterogeneous layer cannot be formed between the active layer and the p-type carrier. - In a semiconductor laser device using Zn as an impurity in the node layer, when the ambient temperature rises to 60 to 70°C, carriers cannot be confined in the active layer, and continuous oscillation cannot be performed.

On the other hand, in Mg (AL, 5Gao, s) o, s
Since a carrier concentration of 1X10'1 cm-'' or higher is obtained at I no, sP and a sufficient heterobarrier can be formed, continuous oscillation is possible up to an ambient temperature of about 90 to 100°C.

However, in the MOCVD method, since Mg does not have an effective organic metal, a solid must be used as a source. Therefore, it is difficult to accurately control the amount of Mg added, and reproducibility is poor. Further, the manufactured semiconductor laser had problems in that its optical output was unstable and it was easily deteriorated.

(c) Problems to be Solved by the Invention Therefore, the present invention provides a highly reliable AjGalnP system that is capable of continuous oscillation at high ambient temperatures, can be manufactured with good reproducibility, provides stable optical output, and has high reliability. The present invention provides semiconductor lasers.

(d) Means for Solving the Problems The present invention is a semiconductor laser comprising an oscillation layer in which an n-type cladding layer, an active layer, and a p-type cladding layer each made of an AjGaInP-based compound semiconductor are laminated, and which solves the above problems. In order to solve the problem, the above p-type LAD layer contains Zn as an acceptor.
It is characterized by having a first layer added with Mg as an acceptor and provided on the active layer, and a second layer added with Mg as an acceptor and provided on the first layer.

(E) Function According to the present invention, the p-type rad layer is doped with Zn as an acceptor and provided on the active layer, and Mg is added as an acceptor and provided on the first layer. By forming the active layer with the second layer, a favorable heterointerface with few defects is formed between the active layer and the p-type rad layer without impairing the confinement of carriers in the active layer.

(f) Example FIG. 1 shows an embodiment of the present invention.

In the figure, (1) is a substrate made of n-type GaAs; (2) is a substrate made of n-type GaAs;
) is a buffer layer made of n-type GaInP with a thickness of 0.5 μm, and (3) is a buffer layer with a thickness of 1.2 μm to which Se is added as a donor.
n-type cladding layer consisting of n-type AjGalnP of pm, (
4) is an active layer made of undoped GaInP with a thickness of 0.08 μm, (5) is a p-type single cladding layer made of p-type AjGalnP with a thickness of 0.07 μm to which Zn is added as an acceptor, and (6) is an acceptor. (7) is a 1.1-μm-thick p-type two-cladding layer doped with Mg, and (7) is a 0.1-μm-thick p-type GaInP contact layer. These layers are deposited on the substrate (
1) is sequentially epitaxially grown on the − main surface. Here, in this example, the n-type cladding layer (3), the p-type cladding layer 1
The carrier concentrations of the cladding layer (5) and the p-shaped 2nd cladding layer (6) are lXl0"Cm-" 4XIQ17(
m-"lXl0"cm-".

In addition, a p-type carved two cladding layer (6) and a contact layer (7
) is selectively etched from the surface of the contact layer (7) until the sum of the thicknesses of the p-type carved first cladding layer (5) and the p-type carved second cladding layer (6) becomes 0.2 μm. A striped ridge (8) with a radius of 5 μm is formed on the p-shaped two-layer cladding layer (6).

(9) is a p-shaped carved two cladding layer excluding the top of the ridge (8) (
6) A block layer made of n-type GaAs epitaxially grown on top, (10) is an exposed p-type 2-cladding layer (6) on top of the ridge (8) and an n-type epitaxially grown on the block layer (9). The cap layer is made of GaAs, and the thickness of each layer is 0.8 μm and 3 μm, respectively. (
11) is Au, Cr formed on the cap layer (10)
(12) is an n-side electrode made of an alloy of Au, Sn, and Cr formed on the other main surface of the substrate (1).

In the device of this example, stable continuous oscillation was obtained up to an ambient temperature of 100°C. In the conventional structure shown in Fig. 4, this is because M
The temperature is approximately the same as when g is used.

Next, a life test was conducted on the device of this embodiment by operating at a constant output of 4 mW at an ambient temperature of 40°C. The results are shown in FIG. 2 as a solid line. For comparison, in the conventional structure shown in FIG. 4, M was used as an impurity in the p-type cladding layer (24)
A comparative device was fabricated using the same conditions as the present example, and a similar life test was conducted. The results are shown in FIG. 2 by broken lines.

From the figure, it can be seen that while the comparison device showed significant deterioration after 500 hours of operation, the device of this embodiment did not experience any deterioration in characteristics over time and was able to obtain stable optical output.

This is because in the comparative example device, Mg is added unstablely at the initial stage of growth of the p-type cladding layer (24), so the active layer (23)
This is thought to be due to the fact that defects are likely to occur at the interface between the p-type cladding layer (24) and the p-type cladding layer (24).

On the other hand, in the device of this embodiment, a p-shaped single cladding layer (5) doped with Zn as an acceptor is provided on the active layer (4). Here, since Zn exists as a liquid organic metal that is stable at room temperature, it is easy to control the amount of Zn added. Therefore, in this example, Zn can be stably added to the p-type 1 cladding layer (5), and the active layer (4) and p-type 1 cladding layer (5) can be stably added.
This is thought to be due to the formation of a good interface with fewer defects between the cladding layer (5) and the cladding layer (5). Moreover, such an effect can be obtained if the thickness of the p-type carved first cladding layer (5) is 0.05 μm or more.

Figure 3 shows the p-type carved 1 cladding layer (5
) shows the maximum oscillation temperature (maximum ambient temperature at which continuous oscillation can be obtained) when the layer thickness is varied. As is clear from the figure, p
The maximum oscillation temperature can be increased if the layer thickness of the first cladding layer (5) is 0.25 μm or less, more preferably 0.2 μm or less.

From the above, the layer thickness of the p-type carved first cladding layer (5) in the present invention is preferably in the range of 0.05 to 0.25 μm, more preferably in the range of 0.05 to 0.2 μm.

(G) Effects of the Invention According to the device of the present invention, the p-type cladding layer is doped with Zn as an acceptor, the first layer provided on the active layer is doped with Mg as an acceptor, and the first layer is doped with Mg as an acceptor. By constructing the semiconductor laser with the second layer provided above, the maximum oscillation temperature can be kept high, and a highly reliable device with less deterioration of the semiconductor laser can be manufactured.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing one embodiment of the present invention, Fig. 2 is a life test characteristic diagram of the device of this embodiment and a comparative example, and Fig. 3 is a layer of one cladding layer with a p-shaped groove in the device of this embodiment. A characteristic diagram showing the maximum oscillation temperature when the thickness is changed, and FIG. 4 is a sectional view showing a conventional device. Figure 2 +000 000 operation time (hoIAy)

Claims (1)

[Claims] (1) In a semiconductor laser including an oscillation layer in which an n-type cladding layer, an active layer, and a p-type cladding layer are laminated, each of which is made of an AlGaInP-based compound semiconductor, the p-type cladding layer is doped with Zn as an acceptor, and the active layer a first layer provided thereon and Mg added as an acceptor;
A semiconductor laser comprising a second layer provided on the first layer.