JPS6244440B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a buried heterostructure semiconductor laser in which the periphery of an I _o G _{a S} P active layer is buried with an I _o P layer.

Buried heterostructure semiconductor laser (BH−
LD (abbreviated as LD) has excellent characteristics such as low oscillation threshold current, stabilized oscillation transverse mode, and ability to operate at high temperatures, so it is attracting attention as a light source for optical fiber communications. The applicant filed a patent application in 1983.
As shown in the specification of No. 123261, _IoGaAsP BH _- LD can reliably form a current blocking layer in areas other than the mesa stripe including the active layer, and therefore has excellent temperature characteristics and improved manufacturing _yield . invented. However, in BH-LDs with this structure, the mesa stripes formed by etching form small protrusions on the entire wafer, which can cause mechanical damage during substrate processing after mesa etching or during the subsequent buried growth process. This led to a decrease in yield.

The purpose of the present invention is to eliminate the _above -mentioned drawbacks by preventing mesa stripes containing an _IoGaAsP active layer that undergoes _radiative recombination from mechanical damage, and to provide a high-performance BH
- It is an object of the present invention to provide a manufacturing method for manufacturing LDs with high yield.

According to the present invention, a semiconductor wafer in which at least an _IoGaAsP active layer and a second _{conductivity type IoP} layer are laminated on a first conductivity type IoP _substrate , a second
A step of removing the conductive type I _o P layer and the I _{o Ga As} P active layer by a selective etching method to form two parallel grooves, and etching the semiconductor wafer in which the grooves are formed with at least a second conductive type. I _o P current blocking layer,
A first conductivity type I _o P current blocking layer is laminated except for only the top surface of the mesa stripe sandwiched between two parallel grooves, and a second conductivity type I _o P buried layer is layered continuously over the entire surface. There is obtained a method for manufacturing a buried heterostructure semiconductor laser, which is characterized in that it includes an epitaxial growth step of stacking layers.

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

FIG. 1 is a sectional view of a BH-LD according to an embodiment of the present invention. To obtain such a BH-LD, first, an n-I _o P buffer layer 102 and a non-doped I _o Ga _{A s} P active layer 10 are formed on a (001) n-I _o P substrate 101.
3. p-I _o P cladding layer 104 (thickness 1 μm)
Two grooves parallel to the <110> direction are formed on a wafer in which the wafers are sequentially laminated using a conventional photoresist technique. These grooves may have a width of about 5 μm, and the interval between the two grooves is set to about 2 μm, and the mesa stripes sandwiched between these two _grooves are recombined by _light emission _. A P active layer 105 is included. In addition, when forming these grooves, a selective etching method was used to first prepare HCl:H ₂ O=4:1.
The p _- IoP cladding layer 104 was removed by etching for 2 minutes at 3° C. using a mixed etching solution of H ₂ SO ₄ :H ₂ O ₂ :H ₂ O=3:1:1. By etching for 1 minute _at 50° C. using a mixed etching solution to remove the _IoGaAsP active layer 103, a groove with a depth up to _{the IoGaAsP active layer} 103 is automatically formed. It will be possible. Filling growth is performed on the semiconductor wafer thus obtained, and the p-I _o P blocking layer 106 and the n-I _o P current blocking layer 107 are removed except for the upper surface of the mesa stripe 150 sandwiched between two grooves. Then p-I
Finally, a _p -I _o G _a A _s P electrode layer 109 is formed so that the P buried layer 108 is continuous over the entire surface.
are sequentially stacked.

In this BH-LD, only one mesa stripe is not formed like a protrusion as in the conventional example, and the substrate is less likely to be damaged by contact with the carbon boat during the buried growth stage, resulting in improved manufacturing yield. Significantly improved. obtained in this way
In BH-LD, the oscillation threshold current at room temperature is
A value of 10 to 20 mA and a differential quantum efficiency of about 50% was obtained with good reproducibility.

In the embodiments of the present invention, the manufacturing method leaves p- _IoP cladding layers on both sides of the mesa stripe including the active layer, so mechanical problems that occur during device fabrication, such as during substrate processing after mesa etching and during buried growth, are avoided. Damage can be prevented, thereby
The manufacturing yield of BH-LD has been significantly improved. The laser obtained in this way has good uniformity and reproducibility, and there is little variation between wafers, and BH-LD
The manufacturing yield has been significantly improved. In the present invention, by adopting a growth method newly developed by the inventors of the present application, n-I o P layers are stacked on both sides of the mesa stripe including the active layer, so that the n-I _o P layer is stacked through this part. No current flows,
Current flows concentrated only in the mesa stripe containing the active layer.

The feature of the present invention is that p- _IoP cladding layers are left on both sides of the mesa stripe containing the active layer in a conventional BH-LD, thereby preventing mechanical damage that occurs during substrate processing and buried growth after mesa etching. could be prevented. Furthermore, since a selective etching method was used for etching grooves when forming stripes, the reproducibility of mesa etching is also extremely good.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a BH-LD device manufactured by the manufacturing method of the present invention. In the figure, 101... n-I _o P substrate, 102...
n- _IoP buffer layer, 103... _{IoGaAsP active} layer, 104 _... p- _IoP cladding layer, 105
...I _o G _a A _s P active layer that emits light and recombines, 106
...p-I _o P current blocking layer, 107...n-
I _o P current blocking layer, 108... p-I _o P buried layer, 109... p-I _o Ga _{A s} P electrode layer, 1
10... p-type ohmic electrode, 111... n-type ohmic electrode.

Claims (1)

[Claims] 1 At least I _{o Ga} on the first conductivity type I _o P substrate
A semiconductor wafer in which an A _s P active layer and a second conductivity type I _o P layer thereon are laminated with the second conductivity type I
_o P layer and the I _{o Ga} A _s P active layer are removed by a selective etching method to form two parallel grooves, and the semiconductor wafer in which the grooves are formed has at least a second conductivity type I _o A P current blocking layer and a first conductivity type I _o P current blocking layer are laminated except for only the upper surface of the mesa stripe sandwiched between the two parallel grooves, and then a second conductivity type I _o P is buried. 1. A method for manufacturing a buried heterostructure semiconductor laser, comprising: an epitaxial growth step in which layers are continuously laminated over the entire surface.