Active solid-state devices (e.g. – transistors – solid-state diode – Incoherent light emitter structure – In combination with or also constituting light responsive...
Reexamination Certificate
1999-07-12
2001-06-05
Tran, Minh Loan (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Incoherent light emitter structure
In combination with or also constituting light responsive...
C257S081000, C257S082000, C257S084000, C257S433000, C257S435000
Reexamination Certificate
active
06242760
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical semiconductor device having both light emission and light reception abilities for use in optical information processing, optical measurement, optical communication, and the like.
2. Prior Art
As optical semiconductor device for use in optical information processing, optical measurement, optical communication, and the like, the one in which a light source and a light-receptive part (photodetector) are mounted in the same package has found use in recent years.
Below, a conventional optical semiconductor device will now be described.
FIG. 13
is a plan view schematically showing the plane layout of a conventional optical semiconductor device.
FIG. 14
is a schematic cross-sectional view taken on line A-A′ of a semiconductor substrate
1
shown in FIG.
13
. Further,
FIG. 15
is a schematic cross-sectional view taken on line B-B′ of the semiconductor substrate
1
shown in FIG.
13
.
Referring now to
FIGS. 13
,
14
, and
15
, the semiconductor substrate
1
is composed of, for example, Si, and it is provided with a rectangular concave portion
1
a
on the surface. A semiconductor laser element
2
is composed of, for example, GaAs, and it serves as light source for emitting signal detection light. The semiconductor laser element
2
is mounted at the concave portion
1
a
of the semiconductor substrate
1
so that the optical axis of the signal detection light is generally in parallel relationship with the surface of the semiconductor substrate
1
, thus to be integral with the semiconductor substrate
1
. Specifically, the semiconductor laser element
2
is fixed on the underside of the concave portion
1
a
.
The above-described concave portion
1
a
is so configured as to reflect the signal detection light of the semiconductor laser element
2
by one inclined side thereof in a direction substantially perpendicular to the surface of the semiconductor substrate
1
. That is, one inclined side of the concave portion
1
a
becomes a reflection surface. Further, the one electrode for applying a voltage to the semiconductor laser element
2
, which is not shown, is formed at the region, on which the semiconductor laser element
2
is mounted, in the underside of the concave portion
1
a
. Whereas the other electrode is formed on the opposite one of the surface of the semiconductor laser element
2
in contact with the underside of the concave portion
1
a.
Each one of the light receiving elements for signal detection
3
,
4
,
5
,
6
,
7
, and
8
is comprised of an impurity diffusion area composed of, for example, Si, and it serves as light-receptive part. It is formed in the semiconductor substrate
1
by impurity diffusion. The light receiving elements for signal detection
3
,
4
,
5
,
6
,
7
, and
8
are selectively formed in the peripheral area of the concave portion
1
a
on the surface of the semiconductor substrate
1
, for example, in the area lateral to the concave portion
1
a
taking the direction of emission of the signal detection light from the semiconductor laser element
2
as forward direction on the surface of the semiconductor substrate
1
. Thus, they receive return light from an optical recording medium.
The above-described semiconductor substrate
1
and each one of the light receiving elements for signal detection
3
,
4
,
5
,
6
,
7
, and
8
are mutually opposite in conductivity type. Between the semiconductor substrate
1
and the light receiving elements for signal detection
3
,
4
,
5
,
6
,
7
, and
8
is applied such a voltage as to result in a reverse bias.
A monitor area
12
comprises an impurity diffusion area composed of, for example, Si, and it is provided in the backward direction of the concave portion
1
a
on the surface of the semiconductor substrate
1
. The quantity of signal detection light from the semiconductor laser element
2
is detected by the monitor area
12
.
The above-described semiconductor substrate
1
and the monitor area
12
are mutually opposite in conductivity type. Between the semiconductor substrate
1
and the monitor area
12
is applied such a voltage as to result in a reverse bias. The impurity concentration of the monitor area
12
is set so as to be comparable to that of the portions of the respective light receiving elements for signal detection
3
,
4
,
5
,
6
,
7
, and
8
.
With this optical semiconductor device, the signal detection light is emitted from the semiconductor laser element
2
substantially in parallel with the surface of the semiconductor substrate
1
as shown by an arrow
9
in FIG.
15
. Then, the signal detection light is reflected by the inclined surface of the concave portion
1
a
existing in front thereof in a direction substantially perpendicular to the surface of the semiconductor substrate
1
, thus to be applied onto an object of signal detection such as optical recording medium.
In this process, the light receiving elements for signal detection
3
,
4
,
5
,
6
,
7
, and
8
are formed at the positions deviating from the direction of emission of signal detection light from the semiconductor laser element
2
. For example, the light receiving elements for signal detection
3
,
4
,
5
,
6
,
7
, and
8
are formed in the area lateral to the concave portion
1
a
taking the direction of emission of the signal detection light from the semiconductor laser element
2
as forward direction, in the surface of the semiconductor substrate
1
. This is achieved for preventing the situation as follows: that is, the signal detection light emitted from the semiconductor laser element
2
enters the semiconductor substrate
1
, resulting in the occurrence of carriers, which adversely affect each signal detection level of the light receiving elements for signal detection
3
,
4
,
5
,
6
,
7
, and
8
. It is noted that, each position of the light receiving elements for signal detection
3
,
4
,
5
,
6
,
7
, and
8
may properly be in the peripheral area of the semiconductor laser element
2
, and that the number thereof may properly be one or more.
For the optical semiconductor device configured as described above, the operation thereof will now be described below. First, the signal detection light emitted from the semiconductor laser element
2
is converged on an optical recording medium (not shown) through an objective lens (not shown). Then, the light corresponding to the signal of the optical recording medium is reflected therefrom to become return light, which is then converged on the light receiving elements for signal detection
3
,
4
,
5
,
6
,
7
, and
8
. Consequently, optical signals are outputted from the respective light receiving elements for signal detection
3
,
4
,
5
,
6
,
7
, and
8
. In this process, the quantity of the signal detection light emitted from the semiconductor laser element
2
is being monitored in the monitor area
12
, during which the semiconductor laser element
2
is controlled so that the value is made constant.
Incidentally, with the above-described prior art configuration, signal detection light is emitted from the semiconductor laser element
2
in a direction shown by the arrow
9
. In addition, unnecessary light other than the signal detection light (below, referred to as stray light) occurs.
Below, a concrete description will now be given to stray light. The light in association with the optical semiconductor device includes laser light emitted from the semiconductor laser element
2
, and return light resulting from reflection from a medium such as optical disk, or magneto-optic disk. However, it is the stray light resulting from the laser light emitted from the semiconductor laser element
2
that matters in the present invention
The laser light emitted from the semiconductor laser element
2
includes the light emitted from the front and the light emitted from the rear, and also includes the effective light and the ineffective light for signal detection.
The laser light, including both the light from the f
Hamaguchi Shin-ichi
Hirose Masanori
Shimizu Yuzo
Tsuruta Toru
Matsushita Electronics Corporation
Stevens Davis Miller & Mosher LLP
Tran Minh Loan
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