JPH11346034A - Method for manufacturing compound semiconductor - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To avoid inactivation of an acceptor by an H group of an arsine AsH ₃ raw material. When a compound semiconductor layer containing As is formed on a p-type compound semiconductor layer, the compound semiconductor layer containing As is formed by supplying an organic arsenic material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a compound semiconductor which is particularly suitable for a cap layer of a semiconductor laser.

[0002]

2. _Description of the _Related Art As a semiconductor laser having a low threshold current Ith, a buried heterojunction type (BH) for confining light and carriers in the lateral direction of the active layer, that is, in the direction orthogonal to the plane direction of the active layer. Type) There is a semiconductor laser.

When manufacturing this type of BH type semiconductor laser, generally, a first conductivity type cladding layer, an active layer, and a second conductivity type cladding layer are sequentially epitaxially grown in the first crystal growth. A double hetero structure is formed, and thereafter, etching is performed across the active layer to form a stripe-shaped projection including a stripe-shaped active layer, a so-called ridge. Then, both sides of the ridge are buried in a second crystal growth to form a BH type. A method of obtaining a semiconductor laser is employed.

However, according to this method, in the operation of removing a part of the active layer by the etching, the remaining end face of the active layer itself is oxidized, which has a serious adverse effect on characteristics and reliability. For the purpose of avoiding such a problem of characteristics and reliability and further complicating workability, the applicant of the present invention has previously described, for example, JP-A-61-183.
No. 987, an SDH (Separ) capable of forming all layers in the first epitaxial growth.
ate Double Hetero Junction) type semiconductor laser.

[0005]

In addition, this type of SD
As an H-type semiconductor laser, the present applicant has
No. 330136 proposes a semiconductor laser, for example, shown in FIG.

[0006] This is because, for example, the GaAs compound semiconductor substrate 11 of the first conductivity type, for example, n-type and one main surface of which has a (100) crystal plane, is orthogonal to the paper surface of FIG.
0) Stripe-shaped mesa projections 2 extending in the crystal axis direction are formed, and ordinary MOCVD (metal organic chemical vapor deposition) is sequentially formed on one main surface of a substrate 11 having the projections.
ition: a chemical vapor deposition method using an organic metal), that is, a metal-based MOCVD, continuously a first conductivity type, for example, an n-type cladding layer 3, a low impurity concentration or undoped active layer 4, and a second conductivity type, for example, a first p-type cladding layer 15 and a first conductivity type, for example, an n-type current blocking layer 1
6 and a second cladding layer 17 of a second conductivity type, for example, a p-type.
And the second conductive type cap layer 18 and each semiconductor layer are formed by a single epitaxial growth.

Here, the first conductive type clad layer 3 and the second conductive type
The first and second conductive type cladding layers 15 and 17 and the first conductive type current blocking layer 16 are made of a material having a larger band gap, that is, a smaller refractive index than the active layer 4. .

In this case, the base 11 and the mesa projection 2
The crystal orientation, the width and height of the protrusion 2, that is, the depth of the mass groove on both sides thereof, and the cladding layer 3 of the first conductivity type;
By selecting the thickness of each layer such as the active layer 4 and the first cladding layer 15 of the second conductivity type, the first layer is formed on the mesa protrusion 2.
The conductive cladding layer 3, the active layer 4, and the second conductive type first cladding layer 15 are formed with a slope by a slope 9 so as to be separated from those on the mesa groove, and are striped by the slope 9. The epitaxial growth layer 10 is formed on the mesa protrusion 2.

This is based on the fact that in the case of ordinary MOCVD, that is, MOCVD using a methyl-based organic metal as a source gas, once a (111) B crystal is generated, epitaxial growth is unlikely to occur on this surface. The stripe-shaped epitaxial growth layer 10 is formed.

In this case, the current blocking layer 16
Both sides of the striped epitaxial growth layer 10 are separated on both sides of the striped epitaxial growth layer 10, and both end faces generated by the separation are both end faces of the striped active layer 4 separated from the others in the striped epitaxial growth layer 10.
That is, the end faces the slope 9.

In this manner, the active layer 4 in the stripe-shaped epitaxial growth layer 10 on the mesa protrusion 2 is formed so as to be sandwiched by the current block layer 16 having a smaller refractive index, and confinement in the lateral direction is performed, so that light emission operation is performed. And the current blocking layer 16 on both sides of the striped epitaxial growth layer 10, the second cladding layer 17 of the second conductivity type, the block layer 16, and the second conductivity type. 1 and the cladding layer 3 of the first conductivity type.
A -npn thyristor is formed, and a current in the thyristor is formed, whereby the current is concentrated on the active layer 4 of the stripe-shaped epitaxial growth layer 10 on the mesa projection 2, and the threshold current is reduced. so that measuring the reduction of I _th.

In addition to the semiconductor laser having the SDH structure as described above, in a semiconductor laser such as an AlGaInP-based or GaInAsP-based semiconductor, the p-type contact layer, that is, the cap layer 18 is formed of GaAs or InGaAs.
In the case of forming by epitaxial growth by MOCVD using a material containing Al, as a raw material of As, arsine As
H ₃ is used.

However, the H of arsine AsH ₃
The group penetrates into the p-type second conductivity type cladding layer 17 during the growth of the p-type cap layer 18 or during a temperature decrease after the growth, and inactivates the acceptor in the p-type second cladding layer 17. I will. As a result, the electrical resistance between the p-type cap layer 18 and the active layer 4 of the stripe-shaped epitaxial growth layer 10 increases, making it impossible to reduce the threshold value or to reduce the p-type. There are problems such as difficulty in controlling the carrier of the cladding layer 17.

Therefore, the present invention provides the above-described arsine AsH
₃ Avoid inactivation of the acceptor by the H group of the raw material,
Lowering the resistance between the p-type cap layer 18 and the active layer 4 and reducing p
Provided is a method for manufacturing a compound semiconductor layer capable of improving characteristics by improving controllability of a mold carrier.

[0015]

According to the method of the present invention, in a step of forming a compound semiconductor layer containing As on a p-type compound semiconductor layer, the compound semiconductor layer containing As is formed by supplying an organic arsenic raw material. Things.

When the compound semiconductor obtained by the method of the present invention is applied to a p-type cap layer, particularly in a semiconductor laser, the p-type cap layer is formed with arsine AsH _3.
Is not used, and it is made of an organic arsenic raw material or the like. Therefore, it is avoided that the acceptor in the p-type cladding layer is inactivated by the H group in AsH ₃ ,
The resistance between the mold cap layer and the active layer is reduced, and the controllability of p-type carriers is improved.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The method of manufacturing a compound semiconductor according to the present invention is a method of forming a compound semiconductor layer containing As on a p-type compound semiconductor layer, particularly by supplying an organic arsenic raw material. is there.

Hereinafter, the method for producing a compound semiconductor of the present invention will be described with reference to an example in which the present invention is applied to a semiconductor laser having an SDH structure. However, the method of the present invention is not limited to the following example.

FIG. 1 is a schematic sectional view of a main part of an example of the semiconductor laser 100. The case of manufacturing a GaInAsP-based III-V compound semiconductor laser will be described as an example.
First, as shown in FIG. 1, a first conductivity type, for example, n-type In
A compound semiconductor 11 such as a P base is provided. The compound semiconductor 11 has a stripe-like shape close to a normal mesa in which both side surfaces 23 have a gentle curved concave surface on the main surface 11A of the compound semiconductor 11 in which one main surface 11A is a (100) crystal plane. It is assumed that the mesa protrusion 2 is formed.

A method for forming the mesa projection 2 will be described. For example, a stripe-shaped etching mask having a required width w is selectively formed on the main surface 11A of the compound semiconductor 11. This mask can be formed by, for example, each process of coating a photoresist film, pattern exposure, and development. In this case, the plane along the plane of the paper is selected as the (011) plane,
The extending direction of the mask stripe is selected in a direction perpendicular to this plane.

Next, the surface 1 of the compound semiconductor 11
From the 1A side, for example, H ₂ SO ₄ and H
Crystallographic etching is performed using an etchant in which ₂ O ₂ and H ₂ O are mixed at a ratio of 3: 1: 1.

In this manner, the etching proceeds from the portion not covered by the mask to form the mesa groove 22, and the above-mentioned mesa protrusion 2 can be obtained. Thereafter, the etching mask is removed, and an n-type buffer layer (not shown) is formed on the uneven surface of the compound semiconductor 11 by MOCVD (not shown) as necessary.
A cladding layer 3 of the first conductivity type such as nP is epitaxially grown.

In this case, as the epitaxial growth progresses, on the upper surface of the mesa projection 2, the slope 9 made of a (111) B crystal plane having an angle of about 55 degrees with the (100) plane is formed.
But spontaneously occur on both sides. Then, in a state where such a slope 9 by the (111) B plane exists,
The epitaxial growth of the n-type cladding layer 3 is stopped.

Subsequently, on the n-type cladding layer 3 having a trapezoidal cross section on the mesa projection 2 by continuous MOCVD,
An active layer 4 made of undoped GaInAsP is epitaxially grown. In this case, (111) B of the slope 9
Since an epitaxial growth layer by MOCVD is unlikely to be formed on the crystal plane, the active layer 4 hardly grows substantially on the slope 9, but only on the mesa protrusion 2 and the bottom surface of the mesa groove 22 on both sides thereof. Alternatively, they can be formed separately from each other.

Next, on the compound semiconductor 11, for example, In
The second conductive type of P, for example, the p-type cladding layer 15 is formed of M
It is epitaxially grown by OCVD. In this case, the growth of the p-type cladding layer 15 proceeds, and the p-type cladding layer 5 is grown on the mesa protrusion 2 to a position where the slopes 9 on both sides cross each other. On the other hand, on the mesa groove 22, the p-type cladding layer 15 is grown to such an extent that both side surfaces 23 of the mesa projection 2 are buried, especially so as not to contact the end face of the active layer 4 on the striped epitaxial growth layer 10.

In this manner, the first conductivity type, that is, the n-type cladding layer 3 is formed on the mesa protrusion 2 of the compound semiconductor 11.
Then, a stripe-shaped epitaxial growth layer 10 in which the active layer 4 and the second conductivity type, that is, the p-type cladding layer 15 are stacked, is formed.

Thereafter, the respective semiconductor layers of the first conductivity type, for example, n-type current blocking layer 16, the second conductivity type, for example, p-type second cladding layer 17, and the second conductivity type cap layer 18 are separated. , Formed by epitaxial growth.

Here, the cladding layer 3 of the first conductivity type and the second
The first and second conductive type cladding layers 15 and 17 and the first conductive type current blocking layer 16 are made of a material having a larger band gap, that is, a smaller refractive index than the active layer 4. .

In this case, the crystal orientation between the substrate 11 and the mesa protrusion 2, the width and height of the protrusion 2, ie, the depth of the mass groove on both sides thereof, and the first conductive type clad layer 3,
By selecting the thickness of each layer such as the active layer 4 and the first cladding layer 15 of the second conductivity type, the first layer is formed on the mesa protrusion 2.
The conductive cladding layer 3, the active layer 4, and the second conductive type first cladding layer 15 are formed with a slope by a slope 9 so as to be separated from those on the mesa groove, and are striped by the slope 9. The epitaxial growth layer 10 is formed on the mesa protrusion 2.

The current blocking layer 16 is divided on both sides thereof by the stripe-shaped epitaxial growth layer 10, and both end surfaces formed by the division are separated from the other in the stripe-shaped epitaxial growth layer 10. , That is, the end faces facing the slope 9.

In this manner, the active layer 4 in the stripe-shaped epitaxial growth layer 10 on the mesa projection 2 is formed so as to be sandwiched by the current block layer 16 having a smaller refractive index, and confinement in the lateral direction is performed, so that light emission operation is performed. And the current blocking layer 16 on both sides of the striped epitaxial growth layer 10, the second cladding layer 17 of the second conductivity type, the block layer 16, and the second conductivity type. 1 and the cladding layer 3 of the first conductivity type.
A -npn thyristor is formed, and a current in the thyristor is formed, whereby the current is concentrated on the active layer 4 of the stripe-shaped epitaxial growth layer 10 on the mesa projection 2, and the threshold current is reduced. so that measuring the reduction of I _th.

A cap layer 18 made of, for example, GaInAsP or InGaAs containing arsenic, for example, As is formed on the second conductivity type, ie, p-type cladding layer 17 shown in FIG. In the process, in particular, as a raw material for supplying As, an organic arsenic raw material, that is, triethyl arsenic or trimethyl arsenic having no H group,
Alternatively, for example, diethyl arsine, tertiary butyl arsine, or the like having an H group but having a low decomposition temperature is used.

Since the arsenic material in this case is used only for forming the p-type cap layer 18, even if a relatively low-purity material is used, it does not affect various characteristics of the semiconductor device, and the arsenic material remains high. A reliable element semiconductor laser can be formed.

Here, each of the layers 3, 4, 15, 16, 17 can be formed by one operation, that is, one crystal growth, by switching the supplied material gas by a series of MOCVD.

Incidentally, if necessary, the optical waveguide layer can be formed in contact with the active layer 4 by continuous MOCVD. Further, the conductivity type of each layer may be the conductivity type on the opposite side from the illustration.

In the above-described example, a case where the present invention is applied to a semiconductor laser having an SDH structure has been particularly described. However, the method of the present invention is not limited to this example, and at least an n-type cladding layer made of a compound semiconductor layer is used. 3, an active layer 4, a p-type clad layer 15 in contact with the active layer 4, and a p-type cap layer 18 containing As formed thereon.

[0037]

According to the method for producing a compound semiconductor of the present invention, when forming a compound semiconductor layer containing As on a p-type compound semiconductor layer, the acceptor based on the H group of the arsine AsH ₃ raw material conventionally used is used. Can be avoided, and when applied to a semiconductor laser, the resistance between the p-type cap layer and the active layer can be reduced, and the controllability and characteristics of the p-type carrier can be improved. Was.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a semiconductor laser having an SDH structure.

[Explanation of symbols]

2 Mesa protrusion, 3 First conductivity type cladding layer, 4 Active layer, 9 Slope, 10 Stripe epitaxial growth layer, 11 Compound semiconductor, 11A main surface, 15 Second conductivity type first cladding layer, 16 Current block layer , 17
A second cladding layer of the second conductivity type, 18 cap layer, 2
2 Mesa groove, 23 side surface, 100 semiconductor laser

Claims (1)

[Claims] In a step of forming a compound semiconductor layer containing As on a p-type compound semiconductor layer, the compound semiconductor layer containing As is formed by supplying an organic arsenic raw material. Manufacturing method.