Active solid-state devices (e.g. – transistors – solid-state diode – Heterojunction device – Light responsive structure
Reexamination Certificate
1999-06-15
2001-08-07
Mintel, William (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Heterojunction device
Light responsive structure
C257S185000, C257S436000, C359S248000, C438S094000
Reexamination Certificate
active
06271546
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor photodetector, and more particularly to a semiconductor photodetector with an increased photo receiving area and exhibiting high speed performances.
Semiconductor waveguide photodetectors have been known as one kind of the photodetectors in the art to which the present invention pertains. One of the conventional semiconductor waveguide photodetectors is disclosed in Japanese laid-open patent publication No 4-268770.
FIG. 1
is a schematic perspective view illustrative of the conventional semiconductor waveguide photodetector. The structure of the conventional semiconductor waveguide photodetector. A semiconductor substrate, on which the conventional semiconductor waveguide photodetector is formed, comprises an n
+
-InP substrate
11
having a carrier concentration of 1×10
18
cm
−3
. A bottom cladding layer
12
is provided on a top surface of the n
+
-InP substrate
11
, wherein the bottom cladding layer
12
comprises an n
+
-In
1-x
Ga
x
As
y
P
1-y
(x=0.33, y=0.7) bottom cladding layer
12
having a carrier concentration of 1×10
18
cm
−3
and a thickness of 2 micrometers as well as having a band gap wavelength of 1.37 micrometers. A core layer
13
is provided on a top surface of the n
+
-In
1-x
Ga
x
As
y
P
1-y
(x=0.33, y=0.7) bottom cladding layer
12
, wherein the core layer
13
comprises an n
+
-In
1-x
Ga
x
As
y
P
1-y
(x=0.35, y=0.76) core layer
13
having a carrier concentration of 1×10
18
cm
−3
and a thickness of 0.1 micrometer as well as having a band gap wavelength of 1.42 micrometers. A top cladding layer is provided on the n
+
-In
1-x
Ga
x
As
y
P
1-y
(x=0.35, y=0.76) core layer
13
. The top cladding layer comprises a first top cladding layer
14
extending on an entire surface of the n
+
-In
1-x
Ga
x
As
y
P
1-y
(x=0.35, y=0.76) core layer
13
, a second top cladding layer
15
selectively extending on a predetermined region of a top surface of the first top cladding layer
14
, and a third top cladding layer
16
extending on an entire surface of the second top cladding layer
15
, so that the second and third top cladding layers
15
and
16
form a ridged portion. The laminations of the first and second top cladding layers
14
and
15
comprise 20 periods of alternating laminations of undoped n
+
-In
1-x
Ga
x
As
y
P
1-y
(x=0.42, y=0.9) layers having a thickness of 0.005 micrometers and having a band gap wavelength of 1.57 micrometers and undoped In
1-x
Ga
x
As
y
P
1-y
(x=0.33, y=0.7) layers having a thickness of 0.01 micrometers and having a band gap wavelength of 1.29 micrometers. The third top cladding layer
16
comprises a p
+
-In
1-x
Ga
x
As
y
P
1-y
(x=0.33, y=0.7) layer having a thickness of 2 micrometers and a carrer concentration of 1×10
18
cm
−3
. An n-electrode
17
is provided on an entire bottom surface of the n+-InP substrate
11
. A p-electrode
18
is provided on an entire bottom surface of the third top cladding layer
16
. The laminations of the n+-InP substrate
11
, the n
+
-In
1-x
Ga
x
As
y
P
1-y
(x=0.33, y=0.7) bottom cladding layer
12
, and the n
+
-In
1-x
Ga
x
As
y
P
1-y
(x=0.35, y=0.76) core layer
13
are in the form of an n-electrode side region. The laminations of the first and second top cladding layers
14
and
15
are in the form of a low carrier concentration intermediate region. The third top cladding layer
16
is in the form of a p-electrode side region. The above undoped In
1-x
Ga
x
As
y
P
1-y
(x=0.42, y=0.9) layers of 0.005 micrometers in thickness and of 1.57 micrometers in band gap wavelength but only in the second top cladding layer
15
in the ridged portion are capable of absorbing a light having a wavelength of 1.55 micrometers to cause a photoelectric transfer. The light having the wavelength of 1.55 micrometers can be absorbed by only the undoped In
1-x
Ga
x
As
y
P
1-y
(x=0.42, y=0.9) layers. This means that the photo receiving area of the above conventional device is small and thus a coupling efficiency of the photodetector is low.
In the above circumstances, it had been required to develop a novel semiconductor photodetector free from the above problems.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a novel semiconductor photodetector free from the above problems.
It is a further object of the present invention to provide a novel semiconductor photodetector having an increased effective photo receiving area.
It is a still further object of the present invention to provide a novel semiconductor photodetector designed to shorten a distance of travel of carriers generated by a photoelectric transfer.
It is yet a further object of the present invention to provide a novel semiconductor photodetector exhibiting improved high speed performances.
It is a further more object of the present invention to provide a novel semiconductor photodetector driven by a low driving voltage.
The present invention provides a compound semiconductor multilayer structure comprising: a plurality of core layers absorbing a light and exhibiting a photoelectric transfer and a plurality of cladding layers, adjacent two of which sandwich each of the core layers so that the core layers are separated from each other by the cladding layers.
REFERENCES:
patent: 5637883 (1997-06-01), Bowman et al.
patent: 5818066 (1998-10-01), Duboz
patent: 6075254 (2000-06-01), Shen et al.
patent: 0 370 830 (1990-05-01), None
patent: 61-030085 (1986-02-01), None
patent: 63-030821 (1988-02-01), None
patent: 4-268770 (1992-09-01), None
patent: 10-090540 (1998-04-01), None
Mintel William
NEC Corporation
Young & Thompson
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