JPH02181491A - Semiconductor light-emitting device - Google Patents

Abstract

PURPOSE:To obtain large optical output even under a high temperature by a method wherein the generation of a leakage current is inhibited and an injection current is concentrated on an active layer by a structure, in which a P-N junction to be used as a leakage current path is eliminated. CONSTITUTION:A semiconductor light-emitting device has a mesa stripe 20 formed by laminating a one conductivity type buffer layer 12, an active layer 13 and an opposite conductivity type clad layer 14 on a semiconductor substrate 11 and opposite conductivity type and one conductivity type buried layers 15 and 16, which are laminated coming into contact to both side surfaces of the stripe 20, and is constituted into a structure in which the layer 15 comes into contact to the layer 12 and does not come into contact to the layer 14 and the layer 16 comes into contact to the layer 14 and does not come into contact to the layer 12. Thereby, a leakage current in a buried semiconductor element is reduced and a current can be concentrated on the active layer. Accordingly, the high-temperature characteristic of the element is improved.

Description

[Detailed description of the invention] 〔overview〕 Regarding the structure of an embedded semiconductor light emitting device.

Reduces leakage current of embedded semiconductor light emitting devices.

The purpose is to concentrate the current in the active layer.

A mesa stripe (20) in which a buffer layer (12) of one conductivity type, an active layer (13), and a cladding layer (14) of an opposite conductivity type are laminated on a semiconductor substrate (11), and a mesa stripe (20) in contact with both sides of the mesa stripe. Laminated opposite conductivity type embedded iJ (15
) and a buried layer (16) of one conductivity type.

The opposite conductivity type buried layer (15) is one conductivity type buffer layer (1
2) and not in contact with the opposite conductivity type cladding layer (14), the one conductivity type buried layer (16) is in contact with the opposite conductivity type cladding layer (14).
14) and not in contact with one conductivity type buffer layer (12).

[Industrial application field]

The present invention relates to the structure of an embedded semiconductor light emitting device.

With the recent progress in optical communication systems, InGaAsP
Embedded semiconductor light emitting devices with active layers have come to be used as light sources for long wavelength optical communications.

Furthermore, the environments in which these light emitting elements are used are becoming increasingly diverse.

For this reason, environmental resistance has become more important in the characteristics required of devices. For example, stable operation under high temperatures, high output oscillation, etc. have become desirable.

Conventionally, this light-emitting element used an n-type tnP substrate, but one using a p-type InP substrate has been attracting attention since it was discovered that it has the above-mentioned excellent high-temperature characteristics. In the case of a p-type substrate, the embedded layer has a pnp structure, which reduces leakage current due to transistor action compared to the npn structure of an n-type substrate. Therefore, in the present invention, the case of a p-type substrate will be explained as an example.

(Prior Art) FIG. 2 is a sectional view of a main part illustrating a conventional example of a semiconductor light emitting device using a p-type InP substrate.

This device is disclosed in Japanese Patent Application No. 130810/1983.

In the figure, 1 is a p-type (p-) InP substrate.

2 is a p-InP buffer layer, and 3 is an InGaAsP active layer.

4 is n-type (n-) InPn type 5, 5 is p-1nP
Embedded layer.

6 is an n-1nP buried layer, and 7 is a p-1nP buried layer.

8 is an n-InPn layer, and 9 is an n-1nGaAsP contact layer.

Further, the cladding layer 4, the active layer 3, and the buffer layer 2 constitute a mesa stripe IO.

In this conventional example, p is placed on the side of + n-InPn pixel 9
By providing the ``-1nP buried layer 5A, +9''-1n
A p-type inversion layer 5B is formed on the side surface of the n-1nP cladding layer 4 by solid-phase diffusion of Zn from the P buried layer 5A, and this becomes a high-resistance layer to cause leakage current on the side surface of the mesa stripe 10. 1, thereby realizing a low threshold current and high luminous efficiency.

[Problem to be solved by the invention]

However, although the device according to the above conventional example has the ρ-type inversion layer 5B for reducing the leakage current A1, a pn junction is not formed between the p-type inversion layer 5B and the n-InP cladding layer 4. Therefore, when the applied current is increased to increase the optical output, the leakage current A1 increases.

Further, since a pn junction is also formed between the n-InP cladding layer 8 and the p''-1nP buried layer 5A above the mesa stripe 10, the leakage current A2 also increases.

Therefore, the injected current should not be concentrated in the active layer.

As a result, luminous efficiency decreases and light output is restricted. The optical output at the time when the luminous efficiency decreases increases as the degree of reduction in leakage current increases.

An object of the present invention is to reduce the leakage current of a buried semiconductor light emitting device having an InGaAsP active layer on a p-InP substrate, for example, and to concentrate the current in the active layer.

[Means to solve the problem]

The solution to the above problem is to create a mesa stripe (20) in which a buffer layer (12) of one conductivity type, an active layer (13), and a cladding layer (14) of the opposite conductivity type are laminated on a semiconductor substrate (11).

A buried layer (15) of opposite conductivity type and a buried layer (16) of one conductivity type are laminated in contact with both sides of the mesa stripe,
The opposite conductivity type buried layer (15) is one conductivity type buffer layer (1
2) and not in contact with the opposite conductivity type cladding layer (14), the one conductivity type buried Ji! (16) is achieved by a semiconductor light emitting device characterized in that it is configured to be in contact with the opposite conductivity type cladding layer (14) and not in contact with the one conductivity type buffer layer (12).

[Effect]

The present invention uses a structure that eliminates the pn junction that serves as a path for leakage current, thereby suppressing the generation of leakage current and concentrating the injection current into the active layer.

〔Example〕

FIG. 1 is a sectional view of a main part of an embodiment of a semiconductor light emitting device using a p-type InP substrate.

An outline of the manufacturing method and its structure will be explained using figures.

In the figure, first two liquid phase epitaxial growth (LPE)
on a p-1nP substrate 11 with a dihedral index χ100).

p-1nP buffer layer 12 (Cd doped, carrier concentration 6×10"c+e-' thickness ~0.5 μm) + InGaAsP active layer 13 (undoped, composition is 1.3 μm in wavelength.

Thickness ~ 0.12 μm) + n-InP cladding layer 14 (Sn-doped, carrier concentration lXl0''cm-' thickness ~
0.5 μm).

InGaAsP cap N (not shown) (undoped,
The composition is 1.2 μm in wavelength.

thickness ~0.05 μm).

grow sequentially.

A SiO □ stripe mask with a width of 3 μm is formed in the <011> direction in a lie, and using this as a mask, the InGa
The AsP cap layer is wet-etched with nitric acid, the n-1nP cladding layer 14 is first wet-etched with hydrobromic acid, and the InGaAsP active layer 113 is wet-etched with nitric acid.

Thereafter, the p-1nP buffer layer 12 is etched using a bromine-based etchant, so that (111
) Expose side A and form mesa stripes 20.

1) FUJITSU Sci, Tech, J.

24, 2. p140 (June 1988).

Note that the stripe mask is made of S by plasma CVD method.
An iO2 film is deposited and patterned using conventional gluing lithography techniques.

Then again by the LPB method.

n-1nP first buried layer 15 (Te doped, carrier concentration 2X1018 cm-'thickness ~ 0.7 μm) + p-1nP second buried layer 16 (Zn doped, carrier concentration 2X10Il1 cm-' thickness ~0.7 μm). 6 μm) were grown sequentially.

At this time, p-1nP under the InGaAsP active layer 13 formed by wet etching with a bromine-based etchant.
Since the (111) A surface exposed on the side surface of the buffer layer 12 is difficult to wet, the n-InP first buried layer 15 is made of InGaAsP.
It does not rise above the active layer 13 and can be separated from the n-InP cladding layer 14.

Further, after removing the stripe mask and cap layer.

n-InP cladding layer 17 (Te doped, carrier concentration lXl0''c+m-' thickness ~0.3 μm) + n-1nGaAsP contact layer 18 (Te doped, carrier concentration 2.4X10''cm-' thickness ~0.3 μm) 2 μm).

After this, although not shown, ohmic contact electrodes are formed on the lower surface of the substrate 11 and the upper surface of the contact layer 18,
Separate the sides of the substrate along the cavity length (in the mesa stripe direction) to complete the laser.

When the device is manufactured in this manner, there is no pn junction on the side surface of the mesa, which serves as a path for leakage current, and the generation of leakage current is suppressed.

Furthermore, since the n-InP first buried layer 15 (current blocking layer) on the mesa side surface can be made thicker than that of the conventional structure, leakage current due to the action of the pnp transistor formed of five layers 16, 15, 12 is reduced. can also be suppressed.

Further, since a buried layer for solid-phase diffusion unlike the conventional example is not required, device formation is easy.

In the embodiment, an example using a P-type substrate with good high-temperature characteristics has been described, but it is clear that similar effects can be obtained with an N-type substrate.

Furthermore, although the InGaAsP/InP-based laser has been described in the embodiments, the present invention also applies to other compound semiconductors.

For example, it can also be applied to AlGaAs/GaAs lasers.

〔Effect of the invention〕

As described above, according to the present invention, leakage current of a buried semiconductor light emitting device can be reduced and current can be concentrated in the active layer.

Therefore, the high temperature characteristics of the element are improved, that is, a large optical output can be obtained even at high temperatures.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of an embodiment of a semiconductor light emitting device using a p-type InP substrate. FIG. 2 is a sectional view of a main part explaining a conventional example of a semiconductor light emitting device using a p-type 1nP substrate. In fig. 11 is a p-1nP substrate. 12 is a p-TnP buffer layer. 13 is a TnGaAsP active layer. 14 is the n-nP 9th layer. 15 is an n-nP first buried layer. 16 is a p-nP second buried layer. 17 is the n-nP 9th layer. 18 is an n-nGaAsP contact layer. 20 is mesa stripe

Claims (1)

[Claims] A mesa stripe (20) in which a buffer layer (12) of one conductivity type, an active layer (13), and a cladding layer (14) of an opposite conductivity type are laminated on a semiconductor substrate (11), and the mesa stripe. has an opposite conductivity type buried layer (15) and a one conductivity type buried layer (16) laminated in contact with both side surfaces of the one conductivity type buffer layer ( 1
2) and not in contact with the opposite conductivity type cladding layer (14), the one conductivity type buried layer (16) is in contact with the opposite conductivity type cladding layer (14).
14) and not in contact with a one-conductivity type buffer layer (12).