JPH0410484A - Manufacture of semiconductor laser - Google Patents

Abstract

PURPOSE:To obtain the products having uniform characteristics by accurately regulating a thickness of a second clad layer consisting of conductive type AlxGa(1-x)As in the manufacture of a semiconductor laser. CONSTITUTION:On a N-type GaAs substrate 1, a first clad layer 2 of N-type AlxGa(1-x)As, an active layer 3 of p-type AlxGa(1-x)As, a second clad layer 4 of a P-type AlxGa1-xAs, an etching stopper layer 11 of n-type AlxGa(1-x)As, and a third clad layer 12 of N-type AlxGa(1-x)As are laminated in order. Then, a resist 10 is formed on the third clad layer 12, followed by etching for exposing the etching stopper layer 11. Next, when a P-type GaAs buffer layer 7 and an N-type GaAs block layer 8 are formed, N-type impurities are diffused in the etching stopper layer 11 at the same time. As a result, the etching stopper layer 11 is inverted from N-type to P-type and all of the second clad layer 4, the etching stopper layer 11 and the third clad layer 12 become P-type AlxGa(1-x)As so that (D) can be regulated accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing a laser using a GaAs semiconductor.

(Prior Art) Conventionally, a semiconductor laser having a configuration as shown in FIG. 2(d) is known. That is, on a substrate 1 made of n-type GaAs, n-type Aj2. A first cladding layer 2 made of Ga++-0As, an active layer 3 made of p-type AlyGa++-y>AS, and a second cladding layer 4 made of p-type AJ2yGa++-x>As are laminated in this order. A striped convex portion 5 extending in a direction perpendicular to the plane of the paper is formed on the upper surface of the paper 4 . Recess 6 on the top surface of second cladding layer 4
includes a buffer layer 7 made of p-type GaAs and an n-type GaAs buffer layer 7.
Flock layers 8 made of As are laminated in order, and a contact layer 9 made of p-type GaAs is formed spanning the tops of the four parts 5 and the upper surface of the block layer 8.

Such a semiconductor laser is manufactured as follows.

First, as shown in FIG. 2(a), a first cladding layer 2, an active layer 3, and a second cladding layer 4 having a thickness of H are laminated in this order on a substrate l, and the second cladding layer 4 is laminated in this order. A striped resist 10 is formed on the upper surface by photolithography.

Next, when the portions of the surface of the second cladding layer 4 that are not covered with the resist 10 are etched by immersion in an etching solution, the portions covered with the resist 10 have a thickness as shown in FIG. 2(b). The remaining portion is etched to a thickness D to form a concave portion 6.

Then, as shown in FIG. 2(C), a buffer layer 7 and a block layer 8 are sequentially laminated in the recess 6, the resist 10 is removed, and the convex portion 5 is removed as shown in FIG. 2(d). A contact layer 9 is laminated over the upper surface and the upper surface of the block layer 8 .

(Problem to be solved by the invention) In the conventional semiconductor laser manufacturing method described above, the progress of the etching process shown in FIG. 2(b) varies depending on the etching method 1 conditions, etc., and it is difficult to control it. Therefore, it is difficult to regulate the thickness D of the second cladding layer 4 in the recess 6 to a predetermined value. As a result, the characteristics of the obtained semiconductor laser, such as the laser beam divergence angle, oscillation threshold current, and external quantum efficiency, were not constant.

This invention attempts to obtain a product with uniform characteristics by accurately defining the thickness of the second cladding layer 4 in the recess 6 of the semiconductor laser as shown in FIG. 2(d). It is something.

[Means to solve the problem]

In the first step of the present invention, a first substrate made of AlxGa(1-x)As of the first conductivity type is placed on the substrate of the first conductivity type.
Cladding layer first, second or intrinsic conductivity type AAyGa (+ −
The active layer is made of IllAs, the second conductivity type is 8Ω, and the second is made of Ga(+-x)As.
A third cladding layer made of the same material as the etching stopper layer of the first conductivity type ALGatI-w>As and the second cladding layer are laminated in this order.

In the subsequent second step, the above-mentioned etching layer is removed from the surface of the third cladding layer using an etching solution having different etching rates depending on the conductivity type, so as to leave a predetermined stripe pattern using a resist formed by photolithography. Etching is performed until the etching stopper layer is reached.

In the third step, the part removed by etching,
In other words, a buffer layer of the second conductivity type and a block layer of the first conductivity type are selectively formed on the exposed etching stopper layer, and the etching stopper layer is formed on the second cladding layer and the blocking layer of the first conductivity type. The first conductivity type is inverted to the second conductivity type by impurities diffused from the third cladding layer and the buffer layer.

In a fourth step, a contact layer of a second conductivity type is formed on the surface of the block layer and the portion of the third cladding layer that has not been etched.

[For production]

In the first step of the present invention, in contrast to the conventional manufacturing method in which three layers, the first cladding layer, the active layer, and the second cladding layer, are laminated on the substrate, the first cladding layer, the active layer, and the second cladding layer are laminated on the substrate. active layer,
A second cladding layer, an etching stopper layer, and a third cladding layer are laminated in this order.

Here, if the initial thickness of the second cladding layer in the conventional manufacturing method is H and the thickness after etching is D, then in this invention, the thickness of the second cladding layer and the etching stopper layer is The sum of the thicknesses of the second cladding layer, the etching stopper layer, and the third cladding layer is selected as H.
choose.

In the subsequent second step, by appropriately selecting the etching solution, it is possible to stop the etching when the etching depth or the etching stopper layer is reached. I can die.

In the third step, when the impurity is diffused together with the formation of the buffer layer and the block layer, the impurity can be diffused from the second cladding layer, the remaining third cladding layer, and the buffer layer into the etching stopper layer. , its conductivity type is the second
and inverted to the same type as the third cladding layer. the result,
The second cladding layer, the etching stopper layer, and the third cladding layer are integrated, and the entire structure is changed to have the same properties as the second cladding layer in a conventional semiconductor laser.

Therefore, the semiconductor laser according to the present invention obtained through the fourth step has exactly the same structure as the conventional semiconductor laser, but the thickness D of the recess in the second cladding layer remaining after etching is precisely defined. It is different in that it is.

As a result, the semiconductor laser according to the present invention can maintain constant properties such as the divergence angle of the laser beam, the oscillation threshold current, and the external quantum efficiency.

(Example) As shown in FIG. 1(a), on an n-type GaAs substrate l,
a first cladding layer 2 of n-type AQxGa<+-x)As;
p-type AUyGa (+-y+As active layer 3 and p-type AL
Ga++-x)As second cladding layer 4 and n-type Alx
An etching stopper layer 11 of Ga(1-x)As and a third cladding layer 12 of p-type AU, Ga++-x)As, which is the same as the second cladding layer 4, are laminated in this order.

Then, a resist 1o is provided on the upper surface of the third cloud layer 12 in the form of stripes perpendicular to the plane of the paper and etched, as shown in FIG. 1(b).

The third cladding layer 12 is removed leaving stripe-shaped protrusions 5, and the etching stopper layer 1 is placed in the recesses 6 formed.
1 is exposed.

As shown in FIG. 1(c), a p-type GaAs buffer layer 7 and an n-type G
At the same time as forming aAs block layers 8 in order,
2nd crust layer 4. When diffusing p-type impurities from the third cladding layer 12 and the buffer layer 7 into the etching stopper layer ll, the etching stopper layer II is changed from n-type to p-type.
As a result, the second cladding layer 4, the etching stopper layer 11, and the third cladding layer 12 are all p-type AJ2. It is integrated into a part made of Ga(,□)As.

As shown in FIG. 1(d), by providing a p-type GaAs contact layer 9 on the convex portion 5 and the block layer 8,
Completes semiconductor laser.

Therefore, first, the total thickness of the second cladding layer 4 and the etching stopper layer 1 is selected to be D.

In the completed semiconductor laser, p-type AJ2xGa (1-X
The thickness of the IAs layer can be defined as D.

〔Effect of the invention〕

As described above, according to the present invention, since the thickness of the portion corresponding to the second cladding layer of a conventional semiconductor laser can be accurately defined, the width angle of the laser beam, the oscillation threshold current, the external quantum efficiency, etc. It is possible to obtain a semiconductor laser with uniform characteristics.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a manufacturing process in one embodiment of the present invention, and FIG. 2 is a sectional view showing a conventional manufacturing process. l...substrate, 2...first cladding layer, 3...
-Active layer, 4...Second cladding layer, 5...Protrusion, 6...Recess (removed portion), 7...Buffer layer, 8...Block Layer, 9...Contact layer, 11...Etching stopper layer, 12...
Third cladding layer. Agent Yusuke Oiwa Masu] Private sale

Claims (1)

[Claims] (1) On the substrate of the first conductivity type, Al_
A first cladding layer made of xGa_(_1_−_x_)As and a first, second, or intrinsic conductivity type Al_yGa
An active layer made of _(_1_-_y_)As, a second cladding layer made of Al_xGa_(_1_-_x_)As of the second conductivity type, and an Al_xGa_(_
1_-_x_) an etching stopper layer made of As;
a step of sequentially laminating a third cladding layer made of the same material as the second cladding layer; a predetermined striped pattern of convex portions formed by photolithography in an etching solution having different etching rates depending on the conductivity type; etching from the upper surface of the third cladding layer until reaching the etching stopper layer so as to leave;
A second layer is selectively added to the area removed by this etching.
A buffer layer of a conductivity type and a block layer of a first conductivity type are sequentially formed, and the etching stopper layer of the first conductivity type is formed by impurity diffusion from the second cladding layer, the third cladding layer, and the buffer layer. a step of inverting the third cladding layer to a second conductivity type; and forming a contact layer of a second conductivity type on the surface of the third cladding layer, spanning the portion of the third cladding layer that was not removed by the etching and the blocking layer. A method for manufacturing a semiconductor laser, characterized in that: