Semiconductor optical device

Details Semiconductor optical device Semiconductor optical device

1999-04-14

2002-06-18

Wille, Douglas A. (Department: 2814)

Active solid-state devices (e.g., transistors, solid-state diode

Incoherent light emitter structure

With heterojunction

C257S094000

Reexamination Certificate

active

06407410

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor optical device obtained by forming a p-n junction on a semiconductor substrate.
2. Description of Related Art
LED (Light Emitting Diode) is an example known as a semiconductor optical device.
In the case of the LED
3300
in
FIG. 33
, a multi-layered substrate, comprised of a GaAs
1−x
P
x
inclined layer
3312
and a GaAs
1−y
P
y
layer
3313
, which are grown by epitaxy on a GaAs substrate
3311
, is used as an n-type semiconductor substrate
3310
. The GaAs
1−x
P
x
inclined layer
3312
is formed such that the phosphorus composition ratio increases as it approaches the top face of the layer. Near the surface of the GaAs
1−x
P
y
layer
3313
, a p-type area
3320
is formed by, for example, selectively diffusing such a p-type impurity as zinc. The surface of the GaAs
1−y
P
y
layer
3313
is covered with a interlayer insulator
3330
, except for a part of the p-type area
3320
. On the area where the diffusion area
3320
is exposed, a p-type electrode
3340
is formed. On the rear face of the GaAs substrate
3311
, an electrode
3350
is formed.
As shown in
FIG. 33
, when the p-type area
3320
is formed by a diffusion method, a p-n junction interface
3321
in the longitudinal direction and a p-n junction interface
3322
in the lateral direction are formed in the semiconductor substrate
3310
. The p-n junction interface
3321
in the longitudinal direction mainly contributes to emission at a deep position in the GaAs
1−y
P
y
layer
3313
. The p-n junction interface
3322
in the lateral direction mainly contributes to emission at a shallow position, that is, near the surface of the GaAs
1−y
P
y
layer
3313
.
A shallow position of the layer
3313
has a high density of crystal defects which are generated by the diffusion of the p-type impurity, therefore the recombination rate of carriers is low, which makes the emission efficiency poor. To increase the emission efficiency of the LED
3300
, causing emission at a deep position of the GaAs
1−y
P
y
layer
3313
is preferable.
However, in the p-n junction interface
3322
, at a very shallow position of the GaAs
1−y
P
y
layer, a microscopic turbulence of forms exists. This turbulence makes the electric field very high and tends to cause a concentration of carriers. Therefore, in the LED
3300
, carriers tend to concentrate at a very shallow position in the layer
3313
, making the emission efficiency poor.
SUMMARY OF THE INVENTION
An object of the present invention is to increase the emission efficiency of a semiconductor optical device.
To achieve this object, a semiconductor optical device in accordance with the present invention comprises: a semiconductor substrate having a first conductive type semiconductor layer; a second conductive area formed in the semiconductor layer by doping a second conductive type impurity, which is a different conductive type from the first conductive type, selectively from the surface of the semiconductor substrate; and an etched area formed at the interface between the second conductive type area and the other area near the surface of the semiconductor substrate.
By forming the etched area, the area near the surface of the semiconductor substrate is removed from the interface between the second conductive type area and the other area. This can improve the emission efficiency of the semiconductor device.


REFERENCES:
patent: 4942439 (1990-07-01), Schairer
patent: 5291037 (1994-03-01), Tanaka et al.
patent: 64-35970 (1999-02-01), None

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