JPH04142091A - Manufacture of semiconductor laser - Google Patents

Abstract

PURPOSE:To efficiently inject a current in an active layer and to obtain an excellent result in laser characteristics by partly diffusing the same conductivity type dopant as a first conductivity type in a direction of a waveguide near an active region. CONSTITUTION:A buried layer 4, a current blocking layer 4, and current blocking layer 5 are grown by an LPE until a mesa is flatly buried in a second epitaxial growth. Then, both sides of a stripe partly remain in a stripe state, the other is covered with an SiN film 11, etc., and partly diffused in a p-type by a vacuum sealing method. The layers 4, 5 are completely separated, the film 11, etc., is removed, and a first clad layer 6, a contact layer 7 are crystalline grown. Thus, the same conductivity type dopant as a first conductivity type is partly diffused in the direction of a waveguide near an active region to perform a high yield in the manufacture of a semiconductor laser to obtain the laser having a stable threshold value, an operating current.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a semiconductor laser, which improves the characteristics of the semiconductor laser and achieves a high yield.

[Conventional technology]

FIG. 4 shows, for example, ELECTRONICS LETTE
RS 21 May1987 Vol, 23.546-
DFB with conventional PPIBH structure shown in 547
1 is a cross-sectional view showing a semiconductor laser that oscillates in Fabry-Bello (FP) mode because no laser diffraction grating is formed; in this figure, 1 is a p-type (p −) I n
P substrate (hereinafter simply referred to as a substrate. The same applies to the others.) 2 is an InGaAsP active layer, 3 is a p-I
nP buried layer, 4 is n-I nP current blocking layer, 5
is p-I n P current blocking layer, 6 and 6' are n-I
nP first cladding layer, 7 is n-I nGaAsP:
+Ntak 1, layer, 8 is Sin, insulating film, 9 is n-side electrode,
10 is a p-side electrode.

Next, a method for manufacturing a semiconductor laser having this structure will be described.

First, the first crystal growth (in consideration of the uniformity of the active layer thickness, MO
(Growth by CVD method is preferable), a double \tero (hereinafter abbreviated as DH) structure is fabricated from the active layer 2 to the first cladding layer 6. At this time, a p-I n P buffer layer having the same conductivity type as the substrate 1 may be grown between the substrate 1 and the active layer 2 . Next, the active layer width is 1.0~
Stripes of mesa grooves (in the direction of the laser waveguide) are prepared to have a thickness of 2.0 μm. Next, in the second crystal growth, L
3. A buried layer having a p-n-p structure on both sides of the stripe using the PE method. After the current blocking layers 4 and 5 are buried and grown to the height of the first cladding layer 6 (about 1 μm thick) on the active layer 2, the first cladding layer 6 is continuously grown.
', contact) layer 7 is grown, and finally an insulating film 8 and an np p-side electrode 9,1° are formed.

The semiconductor laser manufactured as described above has an active layer 2
Since both sides of the active layer 2 have a p-n-'-p structure, the current is efficiently injected into the active layer 2. Further, since the DH structure including the active layer 2 is made into a flat crystal in the first growth, a DFB structure laser can also be easily produced by utilizing the advantage (uniformity) of the MOCVD method.

[Problems to be Solved by the Invention] However, in the conventional semiconductor laser manufactured as described above, the most important point is that the current blocking layer 4 and the first cladding layer 6 are appropriately separated. That becomes a problem. In other words, if they are connected, a current bus from the substrate 1 to the current blocking layer 4 to the first cladding layer 6 will be formed as shown in FIG. Characteristics (thresholds, efficiency.

(operating current). In the conventional manufacturing method, in order to solve this problem, in the second LPE growth step, nn was separated by solid phase diffusion (first doping) from the current blocking layer 5. However, autodoping during crystal growth lacks reproducibility and separation is sometimes impossible, and if the separation is too far, the current bus from the substrate 1 to the buried layer 3 → current blocking layer 5 → first cladding layer 6' increases. , the current injected into the active layer 2 is relatively reduced,
There were some problems, such as the fact that it could be considered to have a negative effect on the characteristics of the device.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a method for manufacturing a semiconductor laser in which current can be efficiently injected into a DH structure having an active layer.

[Means to solve the problem]

The method of manufacturing a semiconductor laser according to the present invention is to partially diffuse a dopant of the same conductivity type as the first conductivity type in the direction of the waveguide near the active region.

[Effect]

In the method of manufacturing a semiconductor laser according to the present invention,
Due to the p-type inversion near the stripe, the substrate -
It is possible to prevent the current bus path from the current blocking layer to the cladding layer, thereby efficiently injecting current into the active layer and reducing the L
・-Brings good results to the characteristics.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional structural diagram showing an embodiment of a semiconductor laser according to the present invention. In FIG. 1, the same reference numerals as in FIG. 4 indicate the same components, and 12 is a p-type diffusion region for nn isolation.

Next, the manufacturing method will be explained according to the manufacturing flow shown in FIGS. 2(a) to (C).

The DH shadow forming mesa stripe formation in the first epitaxial growth is the same as the conventional method. Next, in the second epitaxial growth, the buried layer 3, the current blocking layer 4, and the current blocking layer 5 are grown by LPE until the mesa part is buried flat (see FIG. 2(a). )). Next, leave a stripe shape partially on both sides of the stripe, and leave the rest in a stripe shape.
It is covered with an N film 11, etc., and partially diffused into p-type using a vacuum sealing method. As a result, the current blocking layer 4 and the first cladding layer 6
completely separate it (Fig. 2(b)). Next, SiN film 1
The following steps, such as removing the first cladding layer 6' and crystal growth of the contact layer 7, are carried out in the same manner as in the conventional example (FIG. 2(C)) to obtain the semiconductor laser shown in FIG.

If such a manufacturing method is used, the p-type diffusion region 12 can be formed by a reliable method of sealing diffusion using vacuum, without using the unstable process of O1-doping through crystal growth. It is impossible to create a semiconductor laser with a structure that connects the two. That is, it leads to high yield and stabilization of laser characteristics.

Although the above embodiments were applied to manufacturing F-type and P-type lasers, it goes without saying that the invention can also be applied to semiconductor lasers having a DFB structure.

FIG. 3 shows an example of this. In this figure, 13 is a single layer of n-I nP burr, and 14 is n-InGaAs.
The P guide layer 15 is a diffraction grating. Also in this example,
The p-type diffusion region 12 can be easily provided.

〔Effect of the invention〕

As explained above, the present invention partially diffuses a dopant of the same conductivity type as the first conductivity type in the direction of the waveguide near the active region, so that a high yield can be achieved in manufacturing a semiconductor laser. A semiconductor laser having a stable threshold value and operating current can be obtained.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional structural diagram showing one embodiment of the semiconductor laser of the present invention, FIG. 2 is a cross-sectional view showing the manufacturing process of the semiconductor laser of FIG. 1, and FIG. FIG. 4 is a cross-sectional view of the structure of a conventional semiconductor laser. In the figure, 1 is a p-I n P substrate, 2 is InG
aAs P active layer, 3 is p-I n P buried layer, 4 is n-I n P current blocking layer, 5 is p-1 n P current blocking layer, 6 and 6' are n-1 n P cladding layer, 7 8 is a SiO2 insulating film, 9 is an n-side electrode, 10 is a p-side electrode, and 12 is a p-type diffusion region. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent Masuo Oiwa (2 others) Fig.

Claims (1)

[Claims] In a method for manufacturing a semiconductor laser in which a double heterojunction is provided on a semiconductor substrate having a first conductivity type, an active region is provided in the waveguide direction, and current blocking layers are embedded on both sides of the semiconductor laser, A method for manufacturing a semiconductor laser, comprising the step of partially diffusing a dopant of the same conductivity type as the first conductivity type in a waveguide direction.