JPS61101088A - Manufacture of semiconductor laser - Google Patents

Abstract

PURPOSE:To realize high-yield production of semiconductor lasers with their performance characteristics being stabilized by a method wherein P-N junctions are provided in first-fourth semiconductor layers deposited in lamination on a semiconductor substrate and the forbidden band is narrower in the second semiconductor layer than in the first and third layers. CONSTITUTION:On a semiconductor substrate 11, first-fourth semiconductor layers 12-15 are deposited in lamination, wherein P-N junctions are built. It is so set that the layer 13 is provided with a forbidden band narrower in width than the layers 12, 15. The layer 15, same as the layer 12 in the type of conductivity and provided with a forbidden band wider than that of the layer 13, is exposed to a non-selective etchant in a stripe-geometry mesa-etching process, whereafter an extremely thin film is retained of the layer 15. The extremely thin layer 15, just before being buried, is further etched, in a chemical or vapor phase etching process, until contact is made with the layer 14. After this, a fifth semiconductor layer 19 with its forbidden band similar to or wider than that of the layer 14 and a sixth semiconductor layer 20 with its forbidden band similar to or narrower than that the layer 13 are formed, for the formation of a buried layer.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a semiconductor laser that has a stable transverse mode, a high laser manufacturing yield, and excellent homogeneity of characteristics, and a method for manufacturing the same. . Especially MOCVD
This article relates to a laser based on the (organometallic thermal decomposition method) method and its manufacturing method.

[Background of the invention]

In a conventional semiconductor laser using the MOCVD method, a current confinement layer (n-type GaAs layer) for forming an optical waveguide is formed using a selective mesa etching method. In other words, etching is performed until the p-type Ga, -xAΩxAS layer located below the existing layer is exposed, and using the selectivity of the etchant, the p-type Ga, -xAΩxAS layer is etched.
The manufacturing process resulted in almost no etching of the a, -x AD, and xAs layers. Note that these examples are r
15th Conference on 5oli
d St,ateDevice and Materi
alsJ p, 297.1983.

However, such a highly selective etchant is GaAs
A natural oxide film (native oxide) is formed during etching.
During buried growth by MOCVD, an abnormally high resistance layer often grows at the interface, which adversely affects the electrical and optical characteristics of the laser.

[Purpose of the invention]

The present invention provides a stable laser manufacturing process that does not cause growth interface abnormalities during subsequent buried growth in a semiconductor laser and its manufacturing process using the MOCVD method, particularly in the selective etching process of a current confinement layer when forming a transverse mode control structure. The purpose is to stabilize the characteristics of the manufactured laser device and achieve high yield.

[Summary of the invention]

A drawback of the conventional method is that the use of a selective etching solution causes the formation of a native oxide film. In the present invention, this drawback of the conventional method is compensated for, and Ga, -x A Q YAs, which forms a natural oxide film just by being left in the air,
The present invention provides a manufacturing process that minimizes exposure time. In other words, the present invention provides at least a first . Second. A third and a fourth semiconductor layer are stacked, a PN junction is formed in these stacked layers, and the second semiconductor layer is connected to the first semiconductor layer.
and a fourth semiconductor layer having a forbidden band width set narrower than that of the third semiconductor layer, having the same conductivity type as the first semiconductor layer, and having a forbidden band width narrower than that of the second semiconductor layer. is removed by mesa etching in a stripe pattern using a non-selective etching solution, leaving only a very thin layer.Then, just before buried growth, the already thin layer is chemically etched or vapor phase etched to reach the third semiconductor layer. and then etching a fifth semiconductor layer having a forbidden band width equal to or wider than that of the third semiconductor layer and a sixth semiconductor layer having a forbidden band width equal to or narrower than that of the second semiconductor layer. The present invention provides a semiconductor laser using the MOCVD method, including a step of providing a buried layer buried with a semiconductor layer, and a method for manufacturing the same.

[Embodiments of the invention]

Next, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1(a) to 1(d) are process diagrams showing an embodiment of the manufacturing process of a semiconductor laser according to the present invention.

In FIG. 1(a'), an n-type Ga, -xAQxAs cladding layer 12 (x=0.45, thickness 1.5 to 2.0 μm) which is a first semiconductor layer is placed on an n-type GaAs substrate 11.
, undoped Ga'ly A which is the second semiconductor layer
Q y As active layer 13 (y=0.14, thickness 0.0
5-0.15 pm'), p-type Ga1-x A D' z As cladding layer 14 (x=
0.45, thickness 0.2 to 0.5 μm')', n-type GaAs current confinement layer 15 (thickness 0.3 to 0.5 μm'), which is the fourth semiconductor layer
1.0 μm) is sequentially grown using the MOCVD method. Next, in FIG. 1(b), approximately 2,000 Si02-P205 oxide films are deposited on the current confinement layer 15 by chemical vapor deposition, and then stripes with a width of 5 μm are formed on the oxide film by photolithography. Form. After this, H+1PO4 (phosphoric acid)
.

Existing GaAs was etched with H2O2 (hydrogen peroxide), (CH20H), (ethylene glycol) based etching solution
Etch away 17 leaving about 0.1 μm of the layer. Next, the deoxidized film is removed using an HF (fluoric acid) based etchant.

Next, in FIG. 1(C), immediately before crystal growth by MOCVD, the GaAs current confinement layer 15 is etched using an etching solution of phosphoric acid-hydrogen peroxide and diethylene gellicol.
and p-type Ga, -xA Q xAs cladding layer 14 is 0
．． After removing 18 to 0.15 μm of etch and thoroughly washing with deionized water, it was installed in the MOCVD apparatus and
), the fifth semiconductor layer, P-type cat-Z A
Q z As' 19 (z = 0.45 to 0.55
, thickness 0.8 to 1.2 μm), P which is the sixth semiconductor layer
+ type Ga,,,AflwAq 20 (w=o~o
, 15. A thickness of 0.5 to 2.0 μm) is sequentially grown using the MOCVD method. Further, in this embodiment, chemical etching was used for etching before buried growth, but it can be similarly carried out by a vapor phase etching method using HCI (hydrogen chloride) in an MOCVD apparatus. Next, the P side electrode 21 and n
After forming the side electrodes 22, cleavage was performed to form a semiconductor laser with a cavity diameter of 250 μm.

The above semiconductor laser oscillated in a stable transverse fundamental mode with an oscillation wavelength of 780 nm, a threshold current of 25 to 35 mA, and an optical output of 30 mW.

Although the above embodiment used an n-type substrate, it is also possible to implement the same method using an n-type substrate, and it is also possible to use other materials as the semiconductor material, such as InGaAsP or InGaA QP. It can be implemented. It goes without saying that the active layer may be of a multi-quantum well type, and that distributed feedback type feedback means may also be used.

〔Effect of the invention〕

As described above, the semiconductor laser according to the present invention has at least the first . Second. 3rd degree: A fourth semiconductor layer is stacked, a PN junction is formed in the stacked layers, and the second semiconductor layer is stacked with the first semiconductor layer. A fourth semiconductor layer has a forbidden band width set narrower than that of the third semiconductor layer, has a forbidden band width that is the same as or narrower than that of the second semiconductor layer, and has the same conductivity type as the first semiconductor layer. a step of etching away at least a portion of the fourth semiconductor layer through the stripe formed on the fourth semiconductor layer; and a step of etching away at least a portion of the fourth semiconductor layer through a stripe formed on the fourth semiconductor layer, and immediately before the buried growth using the MOCVD method, a chemical etching method or a step of removing the fourth semiconductor layer by a vapor phase etching method until at least the third semiconductor layer is reached; a fifth semiconductor layer having a forbidden band width that is the same as or wider than that of the third semiconductor layer; By including the step of providing a sixth semiconductor layer having a forbidden band width that is the same as or narrower than that of the second semiconductor layer, it is possible to achieve stable characteristics without a buried interface abnormal layer and at a low cost suitable for mass production. A semiconductor laser can be provided.

[Brief explanation of the drawing]

FIGS. 1(a) to 1(d) are cross-sectional views illustrating the manufacturing process of the semiconductor laser of the present invention. 11... Semiconductor substrate, 12... First semiconductor layer, 1
3... Second semiconductor layer, 14... Third semiconductor layer,
15... Fourth semiconductor layer, 16... Sj, 02
P20h oxide film, 17... etch groove (stripe),
18... Etch groove (stripe), 19... Fifth semiconductor layer, 20... Sixth semiconductor layer.

Claims (1)

[Claims] 1. At least a first, a second, and a third semiconductor substrate on a predetermined semiconductor substrate.
, a fourth semiconductor layer is stacked, a PN junction is formed in the stacked layers, the second semiconductor layer has a narrower forbidden band width than the first and third semiconductor layers, and the second semiconductor layer forming a fourth semiconductor layer having the same or narrower bandgap than that of the first semiconductor layer and having the same conductivity type as the first semiconductor layer; A step of etching away the fourth semiconductor layer leaving a part of it; a step of etching the fourth semiconductor layer until it reaches the third semiconductor layer just before the buried growth; third and fourth semiconductor layers having stripes etched away by a fifth semiconductor layer having a wider bandgap and a sixth semiconductor layer having a bandgap equal to or narrower than the second semiconductor layer; 1. A method of manufacturing a semiconductor laser, comprising the step of providing a buried layer with the upper surface buried. 2. The method of manufacturing a semiconductor laser as set forth in claim 1, wherein the etching immediately before the buried growth is chemical solution etching or vapor phase etching. 3. The above laminated layers and buried layers are formed by metal organic chemical vapor phase epitaxy (MO
A method for manufacturing a semiconductor laser according to claim 1 or 2, characterized in that the semiconductor laser is formed by a CVD method.