JPS61296786A - Semiconductor light-emitting element - Google Patents

Abstract

PURPOSE:To contrive the increase in output power by a method wherein the first layer is formed in sufficient thickness and the second layer is thinly formed in the process in which semiconductor layers are laminated in succession on the substrate having a stepping using a liquid-phase epitaxial method. CONSTITUTION:The mesa part 2, having four steppings on its slunting side, is formed on the surface 100 of an N-type arsenic GaAs substrate 1, and the surface 111 appears on the slunting side of the mesa part 2. An N-type gallium- aluminum-arsenide GaAlAs clad layer 4a is grown on the substrate 1 using the well known liquid-phase epitaxial growing method. At this time, the growing speed differs with the plane direction, and as the growing speed on the surface 11 is higher than that of the surface 100, the grown layer 4c in this pat is formed into the shape parallel with a staircase-like stepping 3, thereby enabling to have s large inclination. Accordingly, when the second growing layer is grown on said crystal, a V-group element is made insufficient on the upper part, because the V-group element, for example, is pulled nearer to the shoulder part, thereby enabling to reduce the growing speed at this part and to thin off the grown layer on the upper part.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the structure of a semiconductor light emitting device, and more particularly to a semiconductor light emitting device that can accommodate higher output.

[Prior art and its problems] For example, one of the methods for increasing the output power of a semiconductor laser is a current excitation region, and by reducing the thickness of the active layer involved in laser light emission, the active layer 14 A structure is conceivable in which the light density within the active layer is reduced by allowing the light emitted by the active layer to seep into a cladding layer provided to sandwich the active layer. As a means for realizing this structure, as shown in FIG. 2, a step portion 12 (mesa portion) is provided on the substrate ll, and a lower cladding layer 13 and an active layer 14 are laminated on this mesa shoulder. There is a known method that takes advantage of the phenomenon in which group III elements are carried away to the shoulders of the mesa, slowing down the growth rate at the top of the mesa. 15 is an upper cladding layer, 16 is a cap layer, and I7 is a Zn diffusion layer. However, in this structure, the effect of attracting group V elements occurs during the growth of the mouth-shaped gallium-aluminum-arsenic (GaA (!As)) cladding layer 13, and the layer becomes thinner at the top of the step of the cladding layer 13. When the aluminum-arsenic (GaACAs) active layer 14 is grown, the slope of the shoulder portion becomes gentle, and there is a drawback that the effect of thinning the layer at the top of the step cannot be expected.

[Object of the Invention] The present invention has been made in order to eliminate the above-mentioned problems, and an object of the present invention is to provide a semiconductor light emitting device that has excellent reliability and can handle high output.

[Structure of the Invention] A semiconductor light emitting device of the present invention is a semiconductor light emitting device formed by sequentially stacking growth layers on a semiconductor substrate having steps by a liquid phase epitaxial growth method, wherein the semiconductor substrate has two or more consecutive steps. It is characterized by having a step.

[Principle of the Invention] In order to achieve the above object, the present invention is configured such that the step (mesa portion) formed on the substrate has a continuous step-like shape of two or more steps. When a semiconductor layer is laminated by epitaxial growth on such a substrate crystal, the first growth layer grows along the step because the growth rate differs depending on the plane orientation. For this reason, when the growth of the first layer is completed, the shape of the upper part of the grown layer clearly retains the shape of the step formed on the substrate, and the slope of the shoulder portion is steep. Therefore, when a second growth layer is grown on this crystal, group V elements, for example, are attracted to the shoulder portion, resulting in a shortage of group V elements in the upper portion, and the growth rate slows down in this portion. Therefore, the characteristic of the mesa structure that the growth layer becomes thinner in the upper part can be fully realized. It is possible to control the layer thicknesses of the first growth layer and the second growth layer by controlling the number of steps formed on the substrate.

[Example] Embodiment I of the present invention will be described below based on the drawings.

FIGS. 1(a) to 1(e) show the manufacturing process of a double heterostructure semiconductor laser to which the present invention is applied. n
A mesa portion 2 having four steps on the oblique side is formed on the (100) plane of the type gallium arsenide (GaAs) substrate I, and the (111) plane appears on the oblique side (see Fig. 1). a
)). Using a well-known liquid phase epitaxial growth method on such a substrate l, n-type gallium aluminum arsenic (G
aAQAs) Grow the cladding layer 4a. At this time, the growth rate differs depending on the plane orientation, and the growth rate on the (111) plane is higher than that on the (100) plane, so the growth layer 4C in this part has a shape that follows the stepped portion 3. This results in a large slope (Fig. 1(b)). Next, a non-doped gallium-aluminum-arsenic (GaA12As) active layer 5a of aluminum (with a small mixed crystal ratio of A) is grown from this cladding layer. 5c, the concentration of arsenic (As) becomes dilute in the mesa upper part 5b.As a result, the growth rate slows down in the mesa upper part 5b and a thin active layer is formed (Fig. 1 (C)). n-type gallium-aluminum-arsenic (GaAσAs) cladding layer 6 (Fig. 1(d));
As) Cap layer 7 is grown sequentially. The p-type gallium, aluminum, arsenic (GaA12
As) A Zn diffusion region 8 is formed so as to reach the cladding layer 6 (FIG. 1(e)). The semiconductor laser manufactured in this manner has a cladding layer 4b having a necessary layer thickness and an active layer 5b which is sufficiently thinned, so that it has a structure suitable for high output. It is clear that such a stepped portion can be formed not only by ordinary chemical etching but also by a well-known method such as RIBE (reactive ion beam etching).

In this embodiment, there were four steps, but it is clear that the thicknesses of the lower cladding layer and the active layer can be controlled to a predetermined value by changing the number of steps.

In addition, gallium, aluminum, arsenic (GaA
Although a &As) type semiconductor laser has been described, it goes without saying that the present invention can be widely applied to semiconductor devices having a stacked structure on a substrate, regardless of the constituent materials thereof.

[Effects of the Invention] As described above, according to the present invention, in the step of sequentially stacking semiconductor layers by liquid phase epitaxial growth on a substrate having steps, the first layer thickness can be maintained sufficiently and the second layer thickness can be increased. Since it is formed to be thin, the reproducibility and reliability of the semiconductor device are greatly improved, and a semiconductor light emitting device with high output can be manufactured.

[Brief explanation of drawings]

FIGS. 1(a) to 1(e) are cross-sectional views showing the manufacturing process of a semiconductor laser to which the present invention is applied, and FIG. 2 is a cross-sectional view of a semiconductor laser having a conventional structure. 1...Substrate, 2...Mesa portion, 3...Step-like stepped portion, 4, Lower cladding layer, 5...Active layer 6...
Upper cladding layer, 7... Cap layer, 8... Z
n diffusion layer. Patent Applicant: Sharp Co., Ltd. Representative Patent Attorney: Mr. Aoki and two others 1G2

Claims (1)

[Claims] (1) A semiconductor light emitting device formed by sequentially stacking growth layers by liquid phase epitaxial growth on a semiconductor substrate having steps, characterized in that the semiconductor substrate has two or more continuous steps. Semiconductor light emitting device.