JPH0194690A - Manufacture of buried type semiconductor laser device - Google Patents

Abstract

PURPOSE:To obtain a narrow activated layer width with good reproducibility and a laser element having good burying layer by reforming a mesa profile into an almost vertical mesa profile by means of dry etching. CONSTITUTION:When preparing a buried semiconductor laser element by providing a mesa profile to a double heterojunction including an activated layer 13, the double heterojunction being buried by a burying layer of semiconductor whose refractive index is smaller than that of the activated layer 13, said mesa profile is reformed into an almost vertical mesa profile by means of dry etching. For example, an n-type InP clad layer 12, a GaInAsP activated layer 13, and a p-type InP clad layer 14 are grown on an n-type InP substrate 11, and the part thus grown is etched by a reactive ion beam etching as far as to the n-type InP clad layer 12. Then a p-type InP current blocking layer 16 and an n-type InP current blocking layer are grown by separating a resist 18, and a p-type InP clad layer 14 or the like are grown by separating an SiO2 layer 15.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a buried semiconductor laser device.

[Conventional technology]

Methods for growing double heterojunction crystals necessary for buried semiconductor laser devices include liquid phase epitaxy (LPE), vapor phase epitaxy (VPE), and molecular beam epitaxy (MBE). Among these methods, metal organic chemical vapor deposition (MOCV)
Method D) is a crystal growth method that is attracting attention because it has excellent mass productivity and excellent controllability of film thickness and composition. This M.O.
In the manufacturing process of a buried semiconductor laser device using the CVD method, for example, as shown in FIGS. 2(a) to (C), an n-type 1nP cladding layer (2) is formed on an n-type ■nP substrate (1). A non-doped GarnAsP active layer (3) is formed on the cladding layer, and a P-type InP cladding layer (4) is formed on the active layer. After forming (5), mesa etching is performed using a wet etching method to remove areas other than the stripe area, and a P-type 1nP current blocking layer (6) is added to that area again. An nP current blocking layer (7) is formed, and finally a p-type Ga
A 1nAsP contact layer (8) is formed. In this structure, the active layer (3) has a smaller refractive index than the active layer.
Because it is embedded by P' layers (6) and (7),
Transverse mode control is possible, and current confinement is InP
This is achieved by utilizing the reverse bias characteristics of the pn junctions of layers (6) and (7), making it possible to achieve a low threshold current.

[Problems with the Prior Art] However, since mesa etching is performed using a wet etching method, there are the following problems. Specifically, it is difficult to control the width of the active layer with good reproducibility, and when selective etching is performed, etching progresses to specific crystal planes, which causes unevenness on the mesa side surface and deteriorates the crystallinity near the active layer. In addition, if the adhesion between the SiO2 film and the semiconductor layer is poor, side etching may occur, resulting in problems such as the formation of voids when growing the buried layer. The purpose of this invention is to provide a method for manufacturing a buried semiconductor laser device that realizes a narrow active layer with good reproducibility and has a good buried layer.

[Means for Solving the Problems and Their Effects] In order to achieve the above object, according to the present invention, the double heterojunction including the active layer is formed into a mesa shape, and the double heterojunction is made larger than the active layer. There is provided a method of manufacturing a buried semiconductor laser device in which the semiconductor laser device is buried with a buried layer of a semiconductor having a small refractive index, wherein the mesa shape is formed substantially vertically by dry etching.

Dry etching allows precise control of the width of the active layer. In wet etching, if the etching is isotropic, side etching occurs in which etching progresses below the resist film by the same dimension as the depth, and the selectivity of materials and crystal planes by chemicals is also high. However, when dry etching is used, selectivity is lost and
Uniform etching is possible for InP and Ga1nAsP, and vertical sidewalls without steps can be obtained at the hetero interface.

〔Example〕

The present invention will be described below based on embodiments shown in the drawings.

FIGS. 1(a) to 1(e) are diagrams illustrating cross-sections of essential parts of an embedded semiconductor laser device manufactured by the manufacturing method according to the present invention in the order of steps.

Next, this manufacturing method will be explained step by step according to the drawings. (1) On the n-type 1nP substrate (11), the MOCV of FIG.
By crystal growth using the D method, an n-type 1nP cladding layer Q2 is formed.
1. GajnA with a composition corresponding to light emission with a wavelength of 1.3 layers m
On the sP active layer side, a P-type 1nP cladding layer (+41) is continuously grown (Fig. 1 (a)). 2 layers of resist (photoresist side, StO□ film 0!0
) form a pattern. (Figure 1(b)) (3) CI
! ,! Reactive ion beam etching (R
IBE), using the two-layer resist as a mask, the n-type 1
Etch up to nP cladding I'IQ21. At this time, the angle between the perpendicular to the wafer and the ion beam is 21
By installing the wafer at an angle such that the wafer is tilted and etching the wafer while rotating it, a substantially vertical etching surface can be obtained. (FIG. 1(C)) (4) By ashing the etched wafer, the uppermost layer of the photoresist mask is removed.

(5) After cleaning the wafer, use the low-pressure MOCVD method (76 Torr) using Sin mask 09 as a mask for selective growth.
r), a p-type InP current blocking layer (16) and an n-type InP current blocking layer 0η are grown. At this time, StO
No crystal growth occurs on the mesa stripe of □ (Fig. 1(d)). (6) After peeling off the SiOz film, the third crystal growth causes p-type 1nP clad N04, p-type GaIn
Grow an AsP contact layer 09). After the third crystal growth, the wafer surface becomes almost flat. (FIG. 1(e)) (7) After forming the electrodes, cut into chips.

Note that the method for manufacturing an embedded semiconductor laser device according to the present invention is not limited to the above embodiments, but mesa etching may be performed by the RIEI method instead of the RIBE method, and C2 gas is used instead of C27 gas as the etching gas.
: A gas added with a gas such as Ar may be used,
Furthermore, instead of the photoresist/SiO□ combination, a combination of TiO, /SiO may be used as an etching mask.The emission wavelength of the active layer is not limited to 1.3-, but is 1.1 to 1.6 The desired “emission wavelength” can be selected.

〔Effect of the invention〕

As explained above, according to the present invention, since the mesa shape is formed by dry etching, it is possible to precisely control the inside of the active layer, and side etching can be avoided, resulting in good embedding. It's an excellent effect of being able to obtain layers.

[Brief explanation of the drawing]

FIGS. 1(a) to (e) are cross-sectional views showing the main parts of a buried semiconductor laser device according to the manufacturing method according to the present invention in the order of steps, and FIGS. 2(a) to (C) are respectively sectional views of the conventional FIG. 3 is a cross-sectional view showing the main parts of a buried semiconductor laser device according to the manufacturing method of FIG. 1.11・=n-type 1nP substrate, 2.12・n-type InP
cladding layer, 3.13...GaInAsP active layer, 4.14.P-type InP cladding layer, 5, 15
- SiO□ film, 6.16-p-type 1nP current blocking layer, 7゜17-n-type 1nP current blocking layer, 8.19・p
type GaInAsP contact layer, 18... photoresist.

Claims (1)

[Claims] A method for manufacturing a buried semiconductor laser device in which a double heterojunction including an active layer is formed into a mesa shape and the double heterojunction is buried with a buried layer of a semiconductor having a refractive index smaller than that of the active layer, wherein the mesa shape is dry etched. 1. A method of manufacturing a buried semiconductor laser device, characterized in that the semiconductor laser device is formed into a substantially vertical mesa.