JPS6132587A - Semiconductor laser and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a semiconductor laser having buried structure, which has the excellent flatness of the surface and is manufactured easily, by forming ridgy second regions in approximately the same height on both sides of a mesa striped first region with n and p clad layers and an active layer and burying p and n type semiconductor layers between the second regions. CONSTITUTION:Ridge regions 21 are formed on both sides of a mesa region 20 containing an active layer 3, and p type InP buried layers 11 and n type InP buried layers 12 are shaped among the regions 20 and 21. In the manufacture of a semiconductor laser, a striped SiO2 film 13 and SiO2 films 14 on both sides in the vicinity of the film 13 are shaped onto the surface of semiconductors in which an n type InP layer 2, an InGaAsP layer 3, a p type InP layer 4 and a p type InGaAsP contact layer 5 are grown onto an n type InP substrate 1 in an epitaxial manner. Inverted mesa etching is executed by a Br methanol solution, and the p type InP layers 11 and the n type InP layers 12 are buried among the mesa region 20 just under the SiO2 film 13 and the ridge regions 21 just under the SiO2 films 14 in the epitaxial manner through LPE growth.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to the structure of a semiconductor laser and its manufacturing method.

Conventional configurations and their problems Various structures have been devised in the past for semiconductor laser structures that are capable of low threshold current and single-mode oscillation, but among them, buried (BH) structure semiconductor lasers have been proposed. Are better.

Below, with reference to the drawings, conventional InGaAsP/I
An nP-based BH tank structure semiconductor laser will be explained.

FIG. 1 is a structural sectional view of a conventional BH tank structure semiconductor laser. In FIG. 1, 1 is an n-type InP substrate, 2 is an n-type InP substrate, and 2 is an n-type InP substrate.
type InP cladding layer, 3 is InGaAgP active layer, 4
5 is a p-type InP cladding layer, and 5 is a p-type InGaAsP contact layer.

The above four layers form the light emitting part of the semiconductor laser, and after forming the striped 8i02 film, reverse mesa etching is performed, and in addition, a buried layer of p-InP layer 6 and n-InP layer 7 is sequentially formed on the side surface of the reverse mesa. It is formed by r, pg growth, and has the effect of current confinement and lateral light confinement from the active layer region. However, in the above structure, the semiconductor surface is not flat but mesa-shaped, and when mounted down on the p-side, the thermal resistance increases due to poor contact between the mount metal and the p-side electrode 9, and the temperature characteristics of the semiconductor laser deteriorate. This results in a negative impact on Also, when wire bonding,
Pressure concentrates on the mesa portion, damaging the active layer 3 and causing deterioration of its characteristics. On the other hand, since the parallelism between the mount and the active layer 3 cannot be achieved with high precision, the emission direction of the laser beam changes.

Therefore, in order to improve the flatness of the semiconductor surface, attempts have been made to add an InGaAs P layer 8 on top of the buried layer. FIG. 2 shows a cross-sectional view of the structure of the BHL/-ZA to which an InGaAsP layer 8 is added. in this way,
Compared to XnP, InGaAs P no L PK growth is
This method takes advantage of the characteristic that the (100) plane can be easily flattened because the growth rate in the horizontal direction is faster than the growth rate in the vertical direction. However, the flatness of the semiconductor surface is not secure and the drawbacks of the structure of FIG. 1 are not largely avoided. Further, since the buried layer 6°7.8 is stacked thickly, a depression is formed on the contact layer 6, and heat dissipation from the active layer 3 becomes poor. In addition, this can be said to be the side structure shown in Figures 1 and 2, but since the degree of flatness of the semiconductor surface is determined by the correlation between the thickness of the buried shrimp layer and the height of the mesa part, strict control of the shrimp thickness is required to reproduce the I have a sexual problem.

OBJECTS OF THE INVENTION In view of the above-mentioned drawbacks, the present invention provides a buried structure semiconductor laser which has a good semiconductor surface flatness and is easy to manufacture.

Structure of the Invention The present invention comprises: 1. A mesa stripe-shaped first region having a p cladding layer and an active layer; and ridge-shaped second regions having approximately the same height on both sides of the first region. The semiconductor laser device is characterized in that p- and n-type semiconductor layers are buried between the first region and the second region to substantially planarize the surface.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 3 shows a cross-sectional view of the structure of a semiconductor laser according to an embodiment of the present invention.

In FIG. 3, 1 is a ]-type InP substrate, 2 is an n-type InP substrate, and 2 is an n-type InP substrate.
cladding layer, 3 is InGa, AgP active layer, 4 is p-type InP cladding layer, 5 is p-type InGaAsP:I:
The structure of the y tact layer is the same as that shown in FIG.

The difference from the conventional example is that ridge regions 21 are provided on both sides of the mesa region 20 including the active layer, and p-type I
This is because an nP substrate layer 11 and an n-type 1nP buried layer 12 are formed. The features of the semiconductor laser configured as described above, including its manufacturing method, will be described below.

First, in Figure 4, n-type InP substrate 1'', second n-type InP substrate,
1nGaAs P layer 3, p-type InP substrate and p-type InG
An aAsP contact layer 6 is formed on the surface of the grown semiconductor.
An 8102 film 14 is formed on both sides near the nutripe-shaped 5102 film 13 and 5i02 film 13. Then, reverse mesa etching is performed using a Br methanol solution to form a shape as shown in FIG. Finally, as shown in FIG. 6, a p-type 1nP layer 11 and an n-type InP layer 12 are buried between the mesa region 20 directly under the 5i02 film 13 and the ridge region 21 directly under the 5i02 film 14 by LPX growth.

In the buried semiconductor laser manufactured by the above manufacturing method, the ridge regions 21 having the same height as the mesa region 20 are provided near both sides of the mesa region 2o, so that the mesa region 20 and the ridge region are effectively 21 and is flat, p-type I
There is no need to planarize the nP substrate 1 and the n-type InP layer 12. Furthermore, even if the n-type InP layer 12 grows abnormally thick due to buried growth and exceeds the surface of the mesa region 20, in the structure of the present invention, 5i02
Using the films 13 and 14 as a mask, the n-type InP layer 12 may be etched to a level equal to or lower than the surface of the mesa region 2o. This is a semiconductor laser with a BH tank structure that greatly simplifies the control of the thickness of the buried layer 6.7 for flattening the semiconductor surface, which is required in the buried LPE growth process in the so-called conventional BH tank structure, and has good flatness. is obtained.

Of course, the characteristics of the semiconductor laser with the structure of the present invention are the same as those of the conventional B.
It is comparable to the H-tank structure and can be manufactured at a high yield.

Effects of the Invention As described above, according to the present invention, the ridge regions 21 are provided near both sides of the mesa region 2o having the active layer 3, and the region 20
By forming the p, n type InP buried layers 11 and 12 between the p and n type buried layers 11 and 21, the semiconductor surface becomes effectively flat, and the p and n type buried layers 11 and 21, which are required in the conventional BH tank structure, are effectively flattened.
．． 12 strict film thickness control becomes unnecessary. Therefore, it has the effect of improving yield and reproducibility while being comparable in 1-1' characteristics to conventional BH tank structure semiconductor lasers. In addition, because the surface is flat, it also eliminates the defects that previously occurred with Makunto.

On the other hand, in the embodiment, an InGaAg P/InP-based laser was explained;
The same can be said for As-based materials.

In addition, the p-type InP layer 11 and the n-type
Although an example is shown in which only the P layer 12 is overgrown, an InGaAs P layer may be added on the n-type InP layer 12.

Furthermore, if the substrate is made p-type, it goes without saying that the conductivity types of the other semiconductor layers are also reversed.

[Brief explanation of the drawing]

1 and 2 are structural cross-sectional views of a conventional BH tank structure semiconductor laser, FIG. 3 is a structural cross-sectional view of a semiconductor laser according to an embodiment of the present invention, and FIGS. 4 to 6 are structural cross-sectional views of a semiconductor laser according to an embodiment of the present invention. FIG. 2 is an explanatory diagram of a method for manufacturing a semiconductor laser in an example. 1...Substrate, 3...Active layer, 11...
...p-type buried layer, 12...n-type buried layer, 20
...Mesa area, 21...Ridge area. Name of agent: Patent attorney Toshio Nakao and 1 other person
1 Figure 2 Figure 3 Figure 4

Claims (2)

[Claims] (1) On a semiconductor substrate, a mesa stripe-shaped first region having an n- and p-gradation layer and an active layer is formed, and a second semiconductor region having approximately the same height as the first region is formed on both sides of the first region. and between the first region and the second region, the first
1. A semiconductor laser characterized in that a pn junction semiconductor layer is buried in a direction opposite to that of a pn junction in a region to substantially flatten the surface. (2) On a semiconductor layer, an n-cladding layer, an active layer, and a p-cladding layer are sequentially epitaxially grown on a semiconductor substrate,
A striped first insulating film and a second insulating film are formed near both sides of the first insulating film, and a semiconductor layer between the first insulating film and the second insulating film is formed on the substrate. Alternatively, a method for manufacturing a semiconductor laser, characterized in that after performing mesa etching up to the cladding layer directly above the substrate, p-type and n-type semiconductor layers are immediately buried and epitaxially grown.