JPS6062174A - Manufacture of semiconductor laser - Google Patents

Abstract

PURPOSE:To make it easier to produce a laser with refractive index waveguide construction by a method wherein, when an InGaAsP/InP semiconductor laser is produced by liquid epitaxial growth, a groove with (111)A face as side is opened from (100) face of a substrate while a current strangulating layer and a beam guide layer are formed by one time growth making use of the difference in the growth characteristics of both surfaces. CONSTITUTION:A P type InP substrate 11 with a surface 11a containing a surface (100) is provided and a mask of an SiO2 film 12 with a stripe window 13 extending in the direction of <0, 1, anti 1> is provided on the surface 11a while a groove 14 with its side 14a to be (111)A surface and its bottom 14b swelled a little bit is formed by etching process using Br2-CH3OH solution. Later the film 12 is removed and firstly an N type InP current strangulating layer 15 is grown on the substrate 11 making use of the dependability of the growth of the substrate 11 and the groove 14 upon surface and secondly a P type InGaAsP beam guide layer 16, an InGaAsP active layer 17 and an N type InP clad layer 18 may be laminated to be grown all over the surface while burying the groove 14.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a method for manufacturing an InGaAsP/InP semiconductor laser using a liquid phase epitaxial growth method.

(Description of Prior Art) First, before entering into the description of the present invention, a conventional method for manufacturing a 1nGaAsP/1nP semiconductor laser using a liquid phase epitaxial growth method will be described with reference to FIG.

Conventionally, as shown in FIG.
An n -1nP substrate 1 having a 00) plane is prepared, this substrate 1 is placed in a liquid phase epitaxial growth furnace, and an n -InP layer 2 which is a first cladding layer is formed on the upper surface la of this substrate 1.
, a 1nGaAsP layer 3 as an active layer, a p-Ir+P layer 4 as a second crat layer, and an n-In as a cap layer.
The four GaAsP layers 5 are sequentially grown by liquid phase epitaxial growth. Next, on the surface 5a of this camp layer 5, for example, a fertilized film (5i02) 6 is deposited, and a window 7 on the stripe is opened in this fertilized film 6 by a normal photorin method. Using this, a Zn diffusion layer 8 for current confinement and transverse mode stabilization is formed up to the second ground layer 4. Thereafter, 10 and - ohmic electrodes 9 and 10 are formed on the diffusion layer 8 and the liquefied film 6, on the lower surface 1b of the substrate 1, and on the second crat layer 4, respectively.

This element is a gain factor waveguide structure.

According to this conventional manufacturing method, as mentioned above, Zn diffusion is used for current confinement and structural mode stabilization.
Because it is difficult to control the diffusion depth, there are many variations in the diffusion depth between manufactured devices.Also, since this device has a gain factor waveguide structure, the transverse mode stability is sufficient. I couldn't get it.

In addition, in this conventional method, the Zn diffusion layer for current confinement and transverse mode stabilization is formed in a separate diffusion process other than the liquid phase epitaxial growth process, making the manufacturing process complicated and time consuming.
However, it also had the disadvantage of poor manufacturing yield.

(Object of the Invention) In order to eliminate such conventional drawbacks, the object of the present invention is to create a refractive material having a current confinement layer and an optical guide layer for transverse mode stabilization by continuous liquid phase epitaxial growth. The present invention provides a method for manufacturing a semiconductor laser having an index waveguide structure.

(Structure of the Invention) In order to achieve this object, according to the present invention, 1, nG
During the process of sequentially and continuously growing each layer of an aAsP/InP semiconductor laser using a single liquid phase epitaxial growth method, a current confinement layer is formed and the crystal is I for the surface
A feature of this method is that the light guide layer is formed by utilizing the difference in the crystal growth rate of nGaAsP.

(Description of an Example) Hereinafter, an example of the method for manufacturing a semiconductor laser of the present invention will be described with reference to FIGS. 2(a) to 3) and FIG.

Fig. 2 is a manufacturing process diagram showing the state of the semiconductor laser at the manufacturing stage as a cross-section taken at the inter-fold plane of the laser or a plane parallel to the inter-fold plane, and Fig. 3 is a diagram of the substrate used in this laser. FIG. 3 is a perspective view illustrating a state in the middle of manufacturing.

In these figures, the dimensions, shapes, etc. of each component are merely shown schematically to the extent that the structure of the present invention can be understood. In addition, hatching representing a cross section is omitted from the drawing.

First, as shown in FIG. 2(a), a p -1nP substrate 1 is
Prepare 1. The upper front surface 11a of this substrate 11 is (10
0) side. Next, as shown in FIG. 2(b), an etching mask layer is provided on the substrate surface 11a.
For example, a film 12 such as Si02 is formed, and then an etching mask layer 12 is formed as shown in FIG. 2(C).
Approximately 2 gr in width using normal photolithography method.
A stripe window 13 of about n length is opened extending in the <011> direction, and the exposed surface 11a of the substrate 11 is exposed to bromine methanol (Br2-CH30) 1 through this window 13.
) to etch. By this etching, a concave groove 14 is formed as shown in FIG. 2(d). next,
As shown in FIG. 2(e), this etching mask layer 1
Remove 2.

Incidentally, the state of the groove 14 in this state is shown in a perspective view in FIG. The side surface 14a of this groove is a (111) A surface, and the cross-sectional shape of this groove 14 is approximately the bottom surface as shown in the figure)4.
1) may be in a slightly raised state, or may be further etched to form a groove with a substantially V-shaped cross section that does not substantially have the bottom surface 14b, or may have other shapes. It may be. In any case, this bottom surface 1
The width of 4b needs to be kept to a width that does not allow InP to grow.

Next, the substrate 11 on which the grooves 14 have been formed is placed in a liquid phase epitaxial growth furnace, and each laser layer is successively formed using the liquid phase epitaxial growth method - times as shown in FIGS. 2(f) to (i). to grow. That is, n-InP M15 (second
Figure (f)), P-InGaAsP as the optical guide layer
layer 16 (FIG. 2 16)), an active layer of InGaA;
sP layer 17 (FIG. 2 17)) and cladding layer 17)
The -1nP layer 18 (FIG. 2(1)) is successively grown by -times of liquid phase epitaxial growth.

During this continuous epitaxial growth, the n -1nP layer 15
is the surface 1 of the substrate 11 due to the plane orientation dependence of the crystal growth rate.
Grows only on 1a. In other words, it is the surface of the substrate 11 (
Although n-1nP crystal grows on the 400) plane, groove 1
4 is sufficiently narrower than the surface 11a of the substrate 11, and the growth rate inside the groove 14, that is, on the side surface 14a which is the (111)A plane, is extremely slow. By selecting a growth time commensurate with the degree of supersaturation at night, the surface 11 of the substrate 11 can be substantially grown as shown in FIG. 2(f).
It is possible to selectively grow n -1nP so that it grows only on the surface a and does not grow inside the trench 14 at all. Subsequently, p-InG is deposited on this n-1nP layer 15 and groove 14.
Grow an aAsP light guide layer 16. In this case, In
Due to the 1m orientation dependence of the crystal growth rate of GaAsP, r
The nGaAsP crystal grows quickly on the (111) A plane, which is the side surface 14a of i+1!14.
Since growth is slow on the −1nP layer 15, the second
As shown in Figure (g), this p-InGaAsP is 1. '7 <Grow-i+
If 1>14, this p-InGaAsP layer is buried and grows thickly.

In this way, each liquid phase epitaxial growth layer is deposited on the substrate 1.
For example, the substrate with these layers is taken out of the growth furnace and the layers are formed on the layer 21 (as shown in D).
l')'! surface 18a'' of 218 and substrate 1]
ohmink electrodes 19 and 2 on the lower surface im+1b, respectively.
0 is deposited and formed.

When an appropriate voltage is applied between the electrodes 19 and 20 of the semiconductor laser thus obtained and an injection current flows, n
-'InP M2S acts as a current confinement layer, so the current flows concentrated only in the groove portion, and transverse mode confinement is also possible, and the laser light is confined inside the groove by the optical power layer 18. The horizontal transverse mode is stabilized. Also, in this structure, the substrate acts as one of the crat layers.

(Effects of the Invention) According to the method for manufacturing a conductor laser of the present invention described above, once a substrate is placed in a growth furnace, this substrate is placed on top of the substrate until all of the required laser layers are epitaxially grown. In the second liquid phase epitaxial growth process, which is not taken out of the growth furnace, a current confinement layer is formed using selective epitaxial growth of InP, and Ga1nAsP is
The difference in crystal growth rate is utilized to form a light guide layer for stabilizing the transverse moat. Therefore, in the method of the present invention,
It has a current confinement layer and an optical guide layer for stabilizing the transverse moat, and oscillates at a low threshold current and is stable, without requiring a Zn diffusion process other than the liquid phase epitaxial growth process as in the past. A semiconductor laser having a refractive index waveguide structure capable of transverse mode oscillation can be manufactured. Furthermore, this method has the advantage that manufacturing is simple, takes little time, and has a high manufacturing yield.

In the above embodiment, a p-1nP substrate was used as the substrate, but it goes without saying that an n-InP substrate may also be used, in which case the conductivity type of each evixial layer is reversed accordingly. It can be manufactured by the method described above by simply following the steps described above.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view for explaining a conventional method for manufacturing a semiconductor laser with a gain waveguide structure having a current confinement layer and a Zn diffusion layer for transverse mode stabilization, and Figures 2 (a) to (''). 1 is a preliminary manufacturing process diagram for explaining an embodiment of a method for manufacturing a semiconductor laser according to the present invention. FIG. 3 is a schematic perspective view for explaining the state of a substrate used in a semiconductor laser to be manufactured according to the present invention during its manufacture. 1, ]...Substrate, 1a, lla... Upper surface of substrate lb, llb... Lower surface of substrate 2... First cladding layer 3, I7... Active layer, 4... Second crack, membrane layer 5...
・Cap layer, 5a...Surface of cap layer 6...Fused film layer, 7...Sliver shaped window 8...Zn diffusion layer, 9,10.1!3.20... - Ohmic electrode 12... Etching mask layer 13... Stripe window, 14... Groove +4a... Side surface of groove, 14b... Bottom surface of groove] 5... Electron JIt constriction layer, ] 6 ... Optical power layer 18 ... Cla, film layer, 1
8a...Kuratu [・Surface of layer. Figure 1 Figure 2 Figure 2 Figure 2

Claims (1)

[Claims] In manufacturing an InGaAsP/InP semiconductor laser using the liquid phase epitaxial growth method, there are two steps: forming a groove whose side faces are from the (100) plane of the InP substrate to the (111) A plane, and the step of forming a groove from the (100) plane of the InP substrate to the (111) A plane. and (111)
Formation of a current confinement layer using the selective growth property of InP with respect to the A-plane and formation of a light guide layer using the difference in the crystal growth rate of InGaAsP between the (100) plane and the (111) A-plane are performed in one step. 1. A method of manufacturing a semiconductor laser, comprising a step of successively performing liquid phase epitaxial growth.