JPS62271485A - Manufacture of semiconductor laser - Google Patents

Abstract

PURPOSE:To obtain a laser oscillated using independent wavelengths of two kinds by forming active layers of two kinds through independent two times of crystal growth. CONSTITUTION:A P-type InP clad layer 12, a GaInAsP active layer 13 and an N-type InP clad layer 14 are shaped onto a P-type InP substrate 11, and grooves 15, 15 holding a mesa stripe 15a in narrow width and a groove 16 holding a mesa stripe 16a in broad width between the grooves 15 are formed through etching. When N-type InP clad layers 17, a GaInAsP active layer 18 and a P-type InP clad layer 19 are shaped, only the clad layer 19 is formed onto the stripe 15a. Grooves 20, 20 reaching the substrate are shaped to groove 15, 15 forming sections, and the insides of the grooves are buried with insulating materials 21, 21. Consequently, the active layer 13 in the stripe 15a and the active layer 18 shaped in the groove 16 function as laser oscillation sections. The active layers 13, 18 are formed independently, thus manufacturing two kinds of semiconductor lasers 24, 25 having independent oscillation wavelengths on the same substrate.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method of manufacturing a semiconductor laser, and in particular, to a method of manufacturing a semiconductor laser, in which two semiconductor lasers emitting different wavelengths are mounted on one substrate. This invention relates to a method of manufacturing a so-called three-wavelength monolithic semiconductor laser that is monolithically integrated.

[Conventional technology]

Three-wavelength monolithic semiconductor lasers (hereinafter referred to as three-wavelength laser arrays) constructed on the same substrate are required in a wide range of fields such as erasable original disk files and wavelength multiplexing communications.

Conventionally, as a method for manufacturing a three-wavelength laser array, the literature 1981 Autumn Proceedings of the Japanese Society of Applied Physics P, 9725, -F
-6 is disclosed.

This conventional example will be explained below based on FIG. In addition, in the figure,
TS indicates a TS type laser, and TR8 indicates a component of a TR8 type laser. First, 21 is n common to both lasers.
- In the GaAs substrate, a terrace-like striped stepped portion 22 is formed in the TS portion, while a dovetail-shaped groove portion 22a'ji7 narrows into two protruding portions (hereinafter referred to as ridges) 22b in the TR8 portion. , 22b are formed.

On this n-QaAs substrate 21, an n
-Ga1-X fiber AS first cladding layer (0<x<1
)23゜n-Ga1-y AtyAS active layer (0<
Y < 1) 24, p-Ga1-xAtX A
A second cladding layer 25 and an n-GaAS separation layer 26 are grown in sequence. After that, 7. n (
Zinc) is fully diffused to form r-diffusion regions 27.27.

Thereafter, the n-side electrode 28 and the p-side electrode 29 are deposited by full vacuum evaporation, and in order to further separate the TS laser and TRS laser, the entire separation groove 30 reaching the n-QaAS substrate 21 is removed by etching, and GaAtAs is deposited. /GaAs-based three-wavelength laser array manufacturing process is completed.

Here, the oscillation region of the TS laser and TRS laser is in the Ga 1-yAtyAS active layer 24.
The slope portion and both ridges 22b on the stepped portion 22, respectively.

This is the upper part of the groove 22a between the grooves 22b. In addition, in the three-wavelength laser array with the above configuration, the oscillation wavelength region of the TS structure grows faster due to the anisotropy of crystal growth, so AtAs
υ, where the mixed crystal ratio is small, shifts to the longer wavelength side by 20 to 30 nm.

[Problem that the invention seeks to solve]

However, in the conventional manufacturing method described above, the active layer is grown on the same substrate using the same growth solution and by utilizing the local speed difference of epitaxial crystal growth in one liquid phase vapor phase growth. We are currently developing a three-wavelength laser beam.

For this reason, there has been a problem in that it is difficult to monolithically manufacture semiconductor lasers whose oscillation wavelengths are completely independent and which cover all different wavelength regions.

Therefore, it is an object of the present invention to solve the above problems and provide a method for manufacturing a three-wavelength monolithic semiconductor laser that emits two completely independent and different wavelengths.

[Means for solving problems]

A method for manufacturing a semiconductor laser according to the present invention includes (a) forming a first cladding on a semiconductor substrate by first crystal growth;
-1 step of completely continuously forming the first active layer and the second cladding layer; (b) forming two substantially parallel first grooves with a narrow first mesa stripe between them by etching; (c) forming a second groove between the first groove and a wide second mesa stripe so as to penetrate through the first active layer; (c) by second crystal growth; A step of successively forming a third cladding layer of a conductivity type different from that of the second cladding layer, a second active layer, and a thick fourth cladding layer; (d) After this, etching is performed. A first semiconductor laser is formed under the first mesa stripe by forming a third groove that reaches the semiconductor substrate through the first groove and filling the third groove with an insulating material. and a step of insulating and separating the second semiconductor laser formed in the second groove, and gold.

[Function] As described above, according to the present invention, the width of the first mesa stripe between the first grooves is narrow, so that the third cladding layer and the second mesa stripe are formed in the second crystal growth. The active layer cannot grow on this, and only the thick fourth cladding layer grows over the entire surface. Therefore, in the first semiconductor laser formed at the bottom of the first mesa stripe, the second cladding layer formed by the first crystal growth and the fourth cladding layer formed by the second crystal growth are formed on the top. It functions as cladding 1 of

Further, when the laser is driven, the first semiconductor laser is affected by the insulating material embedded in the third grooves on both sides, and the second semiconductor laser formed in the second groove is affected by the second insulating material. Due to the p-n junction (reverse bias) formed between the second cladding layer grown on both sides of the second trench including the mesa stripe and the third cladding layer of a different conductivity type, each current The narrowing of the transverse mode can be performed to suppress the expansion of the transverse mode.

Furthermore, since the first and second active layers are formed completely independently by the first and second crystal growth, material selection, film thickness control, etc. can be performed individually.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on FIG.
This will be explained in detail using an sP/InP laser as an example.

First, as shown in the same figure (a), p
- first cladding layer 12 made of nP, GaInAs;
Three gold layers, a first active layer 13 made of P and a second cladding layer 14 made of n-InP, are successively formed to a predetermined thickness, and a first crystal growth is performed.

Next, as shown in FIG. 2B, the OMR resist and the like are etched with bromine-methanol using an etching mask (not shown) to form the first groove 15.15 and the second groove 16. The first groove portion 15. is formed to a depth that is deep enough to penetrate the entire active layer 13.For this reason, the first groove portion 15.
A first mesa stripe 15a1 and a second mesa stripe 16a are formed between the groove portion 15 and the second groove portion 16, respectively.

Here, since the lower part of the first mesa stripe 15a becomes the first semiconductor laser part, the width W1 is required for transverse mode control.
The thickness should be approximately 2.0 μm or less. Further, a second semiconductor laser to be described later is formed in the second groove portion 16, and the groove width Ws t” 2 is set to be approximately 0 μm or less.

The groove width W2 of the first groove part 16 is not particularly limited in terms of manufacturing, and may be a width that allows crystal growth inside this groove, for example, about 5.0 μm (as long as the fine root degree is 1.0 or more). possible). Furthermore, on the second mesa stripe 16a, a second semiconductor current block N is provided as described later.
Since it is necessary to fully grow I, the width @w4 needs to be approximately 4.0 μm or more.

Note that the shapes of the first and second groove portions 15.16 are OMR
Etching with bromo-methanol using a mask results in the result shown in the figure without selectivity between GaInAsP and InP.

Next, as shown in FIG. 6(c), as a second crystal growth, a third cladding layer 17 made of p-InP, a Ga1n
Three layers are successively grown: a second active layer 18 made of AsP and a fourth cladding layer 19 made of n-InP.

Here, the third cladding layer (p-np) 17 is
Inside the second groove 16, there is no cladding layer of the second semiconductor laser, and outside the second groove 16, that is, on both sides including the top of the second mesa stripe 16a, there is no cladding layer of the second semiconductor laser. Clad j# (n-InP) 14
Since the p-n junction between the two is reverse biased, it functions as a current blocking layer. Note that the second crystal growth is not performed on the first mesa stripe 15a because the width Wl is as narrow as about 2.0 μm.

Furthermore, the fourth cladding layer 19 can be formed over the entire surface by growing thickly, and serves as a cladding layer for both the first and second semiconductor lasers.

Next, as shown in FIG. 4(d), a third groove 20.20 reaching the semiconductor substrate 11 is formed from a position above the first groove 15.15 (by etching), and is made of polyimide or the like. It is filled with an insulating material 21 made of insulating resin or 5iOz'4. After this, n
All the ohmic electrodes 22 on the side, and p on the semiconductor substrate 11 side.
The side ohmic electrode 23 is deposited, and the n-side ohmic electrode 22 is further separated for the first and second semiconductor lasers.

As described above, the υ buried type first semiconductor laser 24 and ■
A GaInAsP/InP three-wavelength laser array in which the groove-type second semiconductor laser 25 and the second semiconductor laser 25 are monolithically integrated on the same substrate 11 is completed.

According to the present invention, the conductivity type may be reversed for p and n, and the material may be gold such as A4GaAs/GaAs.

〔Effect of the invention〕

As explained in detail above, according to the present invention, the first and second active layers are formed completely independently by the first and second crystal growth, so that the material Selection and film thickness control can all be done individually. Further, current confinement in the first and second semiconductor lasers is performed using an insulating material and a pn junction.

Therefore, by growing the crystal twice, it is possible to monolithically manufacture the first and second semiconductor lasers, which have a low lasing threshold current, oscillate in the fundamental transverse mode, and have completely independent different wavelengths, on the same substrate. effective.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a process for explaining an embodiment of the present invention;
The figure is a sectional view of a main part explaining a conventional example. 11... Semiconductor substrate (p-InP), 12... First
cladding layer (p-InP), 13...first active layer (GaInAsP), 14...second cladding layer (
n-InP), 15...first groove, 15a...first mesa stripe, 16...second groove, 16a.
...Second mesa stripe, 17...Third cladding layer (p-InP), 18...Second active layer (GaIn
AsP), 19-... fourth cladding layer (n-InP
), 20...Third groove part, 21...Insulating material (polyimide, 5iOz), 22...Ohmic electrode (n side), 23...Ohmic electrode (p side), 24...th 1 semiconductor laser (embedded type), 25... second semiconductor laser (V groove type). 30, Kaisen groove

Claims (1)

[Claims] (1) In a method for manufacturing a semiconductor laser in which two semiconductor lasers emitting different wavelengths are monolithically integrated on the same substrate, (a) a first crystal is grown on the semiconductor substrate by the first crystal growth;
(b) forming two substantially parallel first grooves between a narrow first mesa stripe by etching; and a second wide mesa stripe between the first groove and the second mesa stripe.
(c) forming a third cladding layer having a conductivity type different from that of the first cladding layer; (c) forming a third cladding layer having a different conductivity type from the first cladding layer; (d) forming a third groove reaching the semiconductor substrate through the first groove by etching; a step of insulating and separating the first semiconductor laser formed under the first mesa stripe from the second semiconductor laser formed in the second groove by filling the groove of No. 3 with an insulating material; A method for manufacturing a semiconductor laser, comprising: .