JPH0330386A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To make it possible to obtain a semiconductor laser of stable quality with good reproducibility by a method wherein the laser has an internal reflective region provided with a rib, part of which is etched away to the middle of a light guide layer, and the laser is formed into a constitution, in which the side surfaces of the rib and the internal reflective region are filled with a II-VI compound semiconductor layer. CONSTITUTION:A groove region 107 to reach to the middle of a P-type Ga0.9Al0.1 As light guide layer 104 is formed by performing a photolithography process and an etching process. Then, a striped region 108 shaved off to the middle of a P-type Ga0.9Al0.1As clad layer 105 is formed by performing again a photolithography process and an etching process. Hereupon, an SiO2 thin film is left only on a part which is not etched. Then, a ZnSe layer 109 is selectively grown only on a part, on which the SiO2 thin film is not adhered, by an organometallic chemical vapor growth method. In this case, as there is a large difference between the refractive indexes of a GaAs layer and the ZnSe layer, the effective reflectivity of an internal reflective region becomes high. Thereby, the stability of the wavelength of a laser beam is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor laser used in magneto-optical disks and the like.

[Prior art] Conventionally, a semiconductor laser with an internal reflector was developed in 1984.
A substance with the following structure was known, as reported in the Dempa Shimbun dated December 13, 2013.

As shown in FIG. 2(a), after forming a first reverse mesa groove 208 in a p-GaAs substrate 201 by a photolithographic process and an etching process, an n-GaAs current blocking layer 202 is formed.
using the liquid phase growth method (L iq u id Phase).
The V-shaped groove 207 and the second inverted mesa groove 209 are formed again by an etching process.

Next, the p-GaAlAs clad Jii was formed by LPH again.
203, GaAs active Ji layer 204, n-GaAlAs cladding layer 205, and n-GaAs groove layer 206.

Then, the active layer 204 above the inverted mesa groove 209 gradually curves, and the effective refractive index of this portion changes, so that an internal reflection region is formed.

FIG. 2(b) shows a sectional view taken along line bb' in FIG. 2(a).

[Problems to be Solved by the Invention] However, conventional semiconductor lasers having such a structure can only be manufactured by the LPE method, which is difficult to mass-produce.

Moreover, the manufacturing process is very complicated, and alignment during the second etching is difficult.

In addition, there were various problems such as not knowing the cleavage position when cleaving.

Therefore, the object of the present invention is to solve these conventional problems and to obtain a semiconductor laser having an internal resonator and excellent characteristics.

[Means for Solving the Problems] In order to solve the above problems, the semiconductor laser of the present invention has the following features:
a first cladding layer made of an m-v group compound semiconductor having the same conductivity type as the substrate on a substrate made of a semiconductor having the same conductivity type;
an optical guide layer made of a group compound semiconductor; an active layer made of a ■-v group compound semiconductor; a second cladding layer made of an m-v group compound semiconductor having a second conductivity type; a cap;
In the semiconductor laser, the semiconductor laser has stripe-shaped ribs formed by etching a double heterojunction substrate in which 1. The optical guide layer has an internal reflection area etched away halfway, and the rib side surface and the internal reflection area are 1l-Vl.
It is characterized by being embedded with a group compound semiconductor.

[Example] Embodiments of the present invention will be described below based on the drawings.

FIG. 1(a) is a perspective view of a double heterojunction substrate made on a GaAs substrate etched into a rib shape and embedded with Zn5e. Also, (b) is (a
) is a sectional view taken along line aa'.

Next, the manufacturing method will be explained.

n-Gae, 7Als, a on the n-GaAs substrate 101
As cladding layer 102, GaAs active layer 103, p
-G a a, sA 1 s, +A s light guide layer 10
4. After growing p-Gas, vA 1 e, 3A s cladding 4105 and p-GaAs cap layer 106 by metal organic chemical vapor deposition (hereinafter referred to as MOCVD), a 5i02 thin film is grown by chemical vapor deposition. p-GaA
s cap layer 106.

Next, by performing a photoringraph process and an etching process, I) G a s, sA l s, IA s
It reaches halfway through the light guide layer 104 (forming a groove region 107).

Next, by performing the photoringraph process and etching process again, p −G a 19A le, +A s
A stripe region 108 is formed by cutting down the cladding layer 105 halfway.

Then, the 5i02 thin film remains only in the unetched areas.

Next, the Zn5e layer 109 is formed by 5102 layers using the MOCVD method.
Selective growth is performed only on areas without a thin film.

Finally, the 5j02 thin film was removed using a hydrofluoric acid-based etching solution, and the electrode metals 110 and 111 were vapor-deposited.

Note that the width of the groove region 107 is 15 μm1, and the length of the stripe region 107 is 100 μm and 115 μm1, respectively.
The total length of the chip is 230 μm.

The electrical characteristics of this semiconductor laser include an average threshold current value of 40 mA without an edge protection film, and an m-n efficiency of 60 mA.
%, and the destructive light output value is about 35 mW.

Next, the stability of the oscillation wavelength will be explained.

A semiconductor laser with an internal reflection region is a semiconductor and oscillates in a state where multiple leading wave modes inside the laser generate maximum gain, so unlike ordinary semiconductor lasers, mode hopping is extremely unlikely to occur and a stable oscillation wavelength can be obtained. .

In particular, GaAs and Zn5e each have a refractive index of 3.
Since there is a large difference between 4 and 2 and 9, the effective reflectance of the internal reflection region becomes high, so the wavelength stability is extremely high compared to that made only of GaAlAs.

In the case of this semiconductor laser, mode hopping did not occur within a temperature range of approximately 20°C.

Moreover, the temperature dependence of the oscillation wavelength in this temperature range is 0.0 at an oscillation output of 20 mW. 07 nm/'C.

Above, we have described an example in which an AlGaAs-based double heterojunction substrate is used and Zn5e is used to fill the stripe side surfaces and the internal reflection region. However, this also applies to other types of double-heterojunction gantry substrates such as InP-based. Of course you can use it.

In addition, the filling material is not limited to Zn5e, but can also be ZnS or Z.
It may be a material such as nTe or a mixed crystal thereof.

In particular, when using an AlGaAs-based double heterojunction substrate, using a mixed crystal of Zn5e and ZnS is particularly promising because lattice matching with the substrate can be achieved.

Further, the basic structure of the semiconductor laser can be made low in threshold value by using a buried type method, for example.

[Effects of the Invention] The semiconductor laser of the present invention has the following advantages.

(1) Since it can be manufactured using a simple manufacturing process, products of stable quality can be obtained with good reproducibility.

(2) Since a vapor phase growth method such as the MOCVD method can be used, a uniform product can be manufactured even if a large-area substrate is used. Therefore, the unit price per chip becomes extremely low.

(3) Since the chip pattern is visible when viewing the wafer from above, positioning when separating is extremely easy.

(4) I[-'/Since there is a large difference in refractive index between the I group compound semiconductor and the m-v group compound semiconductor, the effective reflectance of the internal reflection area can be increased, so the width of the internal reflection area can be narrowed.

From the point of view of the single value at which the semiconductor laser oscillates, the internal reflection region is a region that has no gain, so it is preferable that it be shorter.

Moreover, since the effective reflectance increases when there is a large refractive index change over a short width, stable oscillation wavelength characteristics can be obtained.

Further, II-Vl group compound semiconductors generally have a large band gap, and the carrier density can be made extremely small, so that light absorption loss can be made very small.

[Brief explanation of drawings]

FIG. 1(a) is a perspective view of a semiconductor laser for explaining the present invention in detail. FIG. 1(b) is a cross-sectional view of a semiconductor laser for explaining the present invention in detail. FIG. 2(a) is a perspective view of a semiconductor laser for explaining the prior art. FIG. 2(b) is a cross-sectional view of a semiconductor laser for explaining the prior art. 101--.n-GaAs substrate 102...n-Gae, 7A IL3As cladding layer 103=-GaAs active layer 104...p-Gae, 5AIe, tAs optical guide layer 105...p Gaa7AI93As cladding layer 106 ・--p-GaAs cow + 'ybu layer 107...
- Groove region 108...stripe region 109=-ZnSe layer 110...electrode metal 111...electrode metal 20! □...p, -GaAs substrate 201202
・--n-GaAs? l flow blocking layer 203...p-Ga
AlAs cladding layer 204-...GaAs active layer 205-...n-GaAlAs cladding layer 206-
-・n-GaAs cap layer 207...V-shaped groove 208...-First inverted mesa groove 209...Second inverted mesa groove and above Iseto Seiko Epson Corporation

Claims (1)

[Claims] a first cladding layer made of a III-V compound semiconductor having the same conductivity type as the substrate on a substrate made of a semiconductor having a first conductivity type; and a first cladding layer made of a III-V compound semiconductor having the same conductivity type as the substrate;
A light guide layer made of a III-V compound semiconductor;
an active layer made of a group compound semiconductor; a cladding layer made of a second group III-V compound semiconductor having a second conductivity type;
In a semiconductor laser having a striped rib formed by etching a double heterojunction substrate in which cap layers are successively laminated to a depth deeper than the middle of the second cladding layer directly above the active layer, the semiconductor laser etches a portion of the rib into the semiconductor laser. The light guide layer has an internal reflection area etched away halfway, and the rib side surface and the internal reflection area are I
A semiconductor laser characterized by being embedded with a group I-VI compound semiconductor.