JPS60254689A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To improve the yield by reducing the number of processes by a method wherein a non-doped ZnSe single crystal is laminated and removed only in the groove part, thus forming a current stricture layer of desired shape is formed, and a cap layer is formed thereon. CONSTITUTION:The first clad layer 2, an active layer 3, and the second clad layer 4 are successively laminated on a substrate 1, and a non-doped ZnSe single crystal 6 is laminated on the layer 4. Next, the current stricture layer 6 of desired shape is formed by removing only the ZnSe single crystal above the groove. Then, the cap layer 5 made of P type GaAs is formed on the surfaces of the second clad layer 4 and the current stricture layer 6. Finally, the first and second electrodes are formed.

Description

[Detailed description of the invention] (b) Industrial application fields The present invention relates to semiconductor lasers.

(b) Prior Art In recent years, many stripe-structured lasers have been developed in semiconductor lasers aiming at low threshold current and single-transverse mode oscillation.

A typical example thereof is a semiconductor laser called a BCP type proposed by the present inventors in Japanese Patent Application No. 57-60152.

FIG. 1 shows such a BCP type semiconductor laser, and (1) is -
The main surface is an n-type GILAll substrate having a (100) plane, and a groove extending in a direction perpendicular to the plane of the paper is formed on the entire surface of the substrate. (2) is a first cladding layer laminated on the whole surface of the substrate [11], and this layer is made of n-type Ga 1-x
A, gxAs (,0<x<1) (+7) The surface shape is formed so that the thickness inside the groove is thicker than the thickness in other parts so that the upper part of the groove is depressed. (3) is an active layer laminated on the first cladding layer (2), and the layer u/y
It is made of doped Gat-yAj7yAs (0≦Y<X), and its planar shape is approximately the same as that of the first cladding layer (2). (4) is a second cladding layer laminated on the active layer (3), and this layer is a P-type Ga1-xAl: x A s
The surface shape is flat. (5) is P-type Ga
The cap layer is made of As, and the cap layer is formed on the second cladding layer (4) on the monument and has a stripe shape extending in the direction perpendicular to the plane of the paper.

+61 is a current confinement layer made of non-doped Zn5e single crystal, and the constriction layer is formed on the second cladding layer (4) on both sides of the cap layer (5) so as to bury it. (
7) is a first electrode laminated on the cap layer (5) and the constriction layer (6), and the box 1 electrode is laminated on the cap layer (5).
This results in ohmic contact. (8) is a second electrode that makes ohmic contact with the other main surface of the substrate (11).

In such a semiconductor laser, when a forward bias is applied between the first and second electrodes 17) and (81), the current is constricted in the cap layer (5) because the constriction layer [61] has a high resistance. ) is the main current path, and in the active layer (3) located in this path, a single-transverse mode laser beam is oscillated at a low current.In addition, in the manufacturing of this semiconductor laser, once the growth process such as a diffusion process is Since there is no step of exposing the layer to high temperatures, thermal deterioration does not occur, and since the lattice number and thermal expansion coefficient of each layer constituting the semiconductor laser are approximately the same, there is no risk of crystal distortion etc. layer(
6) is made of Zn5s, a material with high thermal conductivity, which increases the heat dissipation effect. As described above, this semiconductor laser has excellent characteristics.

However, in such a semiconductor laser, in order to form the cap layer (5) and the current confinement layer (6), (1) P-type GaAB6 is coated on the entire surface of the second cladding layer (4).
Forming step (11) Step (ill) of etching away the P-type GaAs except for the upper part of the monument to form a cap layer (5) of a desired shape (ill) Step Gv of laminating a non-doped Zn5e single crystal on the second cladding layer (4)) Step Gv of etching and removing the Zn5e single crystal on the cap layer (5) to form a desired current confinement layer (6) 04 steps This large number of steps makes it difficult to improve the yield of single-conductor lasers.

(c) Purpose of the Invention The present invention has been developed in view of the above points, and an object thereof is to provide a semiconductor laser which has the excellent features of the semiconductor laser shown in FIG. 1 and which can reduce the number of manufacturing steps. It is something to do.

-) Structure of the Invention Conventionally, GaAl was once exposed to air! As single crystal surface v
It was said that QaAs single crystals do not grow. However, the present inventors discovered the above GaAl! We succeeded in growing the rCGaAs single crystal on Ga by vapor depositing VcGa on the As single crystal and using molecular beam epitaxial growth with the surface of the GaA7As single crystal melted back into the Ga. By melting back from ViGaVc, GaAl! It is thought that this is because oxygen molecules on the surface of the As single crystal can be removed.

The present invention has been made based on this knowledge, and its main features include a semiconductor substrate having a first conductivity type, an active layer for oscillating a laser, and a bandgap energy that is smaller than that of the active layer. The first cladding layer, the active layer, and the second cladding layer are sequentially laminated on the substrate, and the outermost part of the second cladding layer is provided. In the semiconductor laser made of GaAj7As single crystal, a current confinement layer having stripe openings and substantially high resistance is laminated on the surface of the second cladding layer,
Further, a cap layer made of GaAs single crystal is laminated on the constriction layer and the surface of the second cladding layer exposed through the opening.

(E) Embodiment FIG. 2 shows an embodiment of the present invention, and the only structural difference from the conventional example shown in FIG. 1 is that the cap layer (5) and the entire constriction layer (6) are also laminated. It is a point. Note that the same parts in FIG. 2 as in FIG. 1 are given the same numbers and their explanations will be omitted.

Next, the cap layer (5) and the constriction layer (6) in this example
The formation of this will be explained using FIGS. 3A and 3C.

First, as shown in FIG. 6A, a first cladding layer (2
), an active layer (3), and a second coated layer (4) are prepared. A substrate (1) is prepared, and a non-doped Zn5e single crystal (6) is laminated on the entire surface of the second cladding layer +47.

The growth of such a Zn5e single crystal (6) uses molecular beam epitaxial (MBE) growth, and the growth conditions are 1O-8To.
In a vacuum chamber at rr or higher, the substrate temperature is 350°C, Z
The n7-x temperature is 300°C, and the Se7 temperature is 210°C.

Next, as shown in FIG. 6B, only the Zn5e single crystal above the groove is removed to form a current confinement layer (6) having a desired shape. The above removal was performed after forming a mask made of a resist with an open top on the Zn5e single crystal, and then N a OH:H20=1
: Performed by etching using the mixture of 1.

Thereafter, as shown in FIG. 6CVc, a cap layer (5) made of P-type GaAs is formed on the surface of the second cladding layer (4) and the current confinement layer (63).

The formation of the cap layer (5) is performed using MBE growth. First, while holding the substrate at 400°C in a container evacuated to 10-'Torr or less, 500 to
Let it grow to about 100 CIA. The Ga temperature at this time was 900°C. Thereafter, while maintaining temperature equilibrium, the substrate temperature was raised to 550° C. at a rate of 3° C. per minute or less, and maintained for 15 minutes. This results in the second cladding layer (4
) surface melts back into Ga, and therefore the aluminum oxide film generated on the surface of the second cladding layer (4) after forming the current confinement layer (61) also melts back into Ga, and its oxygen molecules melt back into Ga. It is removed from the melt.It should be noted that if the layer thickness of G& is set to 1000λ or more, the amount of meltback increases, which is not preferable.After that, Ga is coated with a temperature of 900°C, a temperature of 250°C, and a temperature of 250°C. P under the condition of source temperature 800℃
A cap layer (51) made of GaAs single crystal is grown.

After forming the cap layer (5), the first and second electrodes (7) f
By forming 81, the element shown in FIG. 2 is obtained.

As described above, in the semiconductor laser of this embodiment, the current confinement layer (6) and the cap layer (5) can be formed in approximately three steps, so the number of steps is reduced and the yield is improved compared to the conventional method. In fact, in the conventional VCH structure, the yield was less than 70%, but in the structure of this embodiment, it increased to more than 80%.

It should be noted that the operation and characteristics of this embodiment are completely the same as those of the conventional one, so the explanation will be omitted.

(F) Effects of the Invention The semiconductor laser of the present invention has many advantages, such as a lower threshold current which can be reduced to a certain extent compared to the conventional one, and thus improved yield.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a conventional example, FIG. 2 is a sectional view showing an embodiment of the present invention, and FIGS. 3A and 3C are sectional views showing the manufacturing process of this embodiment. (1)...Substrate, (2)...First cladding layer, (3
)...Active layer, (4)...Second cladding layer, (5)
... Cap layer, (6) ... Current confinement layer. Applicant Sanyo Electric Co., Ltd. Representative Patent Attorney Shizuo Sano

Claims (1)

[Claims] (11 A first semiconductor substrate having a conductivity type, 6 an active layer for oscillating a laser, and first and second cladding layers having a larger band gap energy and a smaller optical refractive index than the active layer). In the semiconductor laser, the first cladding layer, the active layer, and the second cladding layer are sequentially laminated on the substrate, and the outermost surface of the second cladding layer is made of GaAl!As single crystal. A current confinement layer having a stripe opening and having substantially high resistance is laminated on the layer surface, and a cap layer made of GaAs single crystal is laminated on the surface of the second cladding layer exposed by the constriction layer and the opening. A semiconductor laser characterized by: