Active solid-state devices (e.g. – transistors – solid-state diode – Responsive to non-electrical signal – Electromagnetic or particle radiation
Reexamination Certificate
2001-10-30
2004-05-18
Jackson, Jerome (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Responsive to non-electrical signal
Electromagnetic or particle radiation
C257S459000, C257S466000, C257S436000
Reexamination Certificate
active
06737718
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor photodetector, and more particularly to a waveguide semiconductor photodetector to be used for a light receiving module or a light transmitting module in an optical communication system.
2. Description of the Related Art
Research and development to the waveguide semiconductor photodetector have been progressed (or a light receiving module or a light transmitting module in an optical communication system. The waveguide semiconductor photodetector has an optical absorption layer. A light is incident in parallel to a surface of the optical absorption layer. Even if the optical absorption layer is designed to be thin for obtaining high speed performances, then a sufficiently long waveguide length of the optical absorption layer ensures a high photoelectric conversion efficiency. The waveguide semiconductor photodetector may be designed for obtaining both a high speed response due to a shortened carrier traveling time and a high photoelectric conversion efficiency.
One of the conventional waveguide semiconductor photodetector is disclosed in Third Optoelectronics And Communications Conference Technical Digest, July 1998, pp. 354-355.
FIG. 1
is a fragmentary cross sectional elevation view illustrative of a conventional waveguide semiconductor photodetector.
An n+−InP cladding layer
102
overlies a semi-insulating InP substrate
101
. An n+−InAlGaAs optical guide layer
103
overlies on a selected region of the n+−InP cladding layer
102
. The n+−InAlGaAs optical guide layer
103
has a thickness of 0.8 micrometers, and also has a refractive index which is an intermediate level between a core layer and a cladding layer. An i-InGaAs optical absorption layer
104
overlies the n+−InAlGaAs optical guide layer
103
. The i-InGaAs optical absorption layer
104
has a thickness of 0.5 micrometers. A p+−InAlGaAs optical guide layer
105
overlies the i-InGaAs optical absorption layer
104
. The p+−InAlGaAs optical guide layer
105
has a thickness of 0.1 micrometer. A p+−InP cladding layer
106
overlies the p+−InAlGaAs optical guide layer
105
. A p+−InGaAs contact layer
107
overlies the p+−InP cladding layer
106
. The lamination of the n+−InAlGaAs optical guide layer
103
, the i-InGaAs optical absorption layer
104
, the p+−InAlGaAs optical guide layer
105
, the p+−InP cladding layer
106
and the p+−InGaAs contact layer
107
forms a waveguide mesa structure.
A silicon nitride film
108
extends over the n+−InP cladding layer
102
and also on side walls and a top of the waveguide mesa structure. The silicon nitride film
108
has a first opening over the p+−InGaAs contact layer
107
, and second and third openings over the n+−InP cladding layer
102
. N-electrodes
110
are provided in the second and third openings over the n+−InP cladding layer
102
. A p-electrode
109
is provided in the first opening over the p+−InGaAs contact layer
107
.
The n-electrodes
110
are provided in contact with the n+−InP cladding layer
102
relatively near the waveguide mesa structure so as to reduce a parasitic resistance. The i-InGaAs optical absorption layer
104
is designed to be thin, for example, at 0.5 micrometers in order to obtain a high speed response with a cut-off frequency of not less than 40 GHz at 3 dB-down. The waveguide structure ensures a high photoelectric conversion efficiency at 77%.
The above-described conventional waveguide semiconductor photodetector may reduce, a device resistance. The waveguide mesa structure is directly coated with a thin silicon nitride film, whereby a heat radiation characteristic is poor. An incidence of a high power light into the device is likely to result in an undesirable heat accumulation which may deteriorate or break the waveguide semiconductor photodetector.
In the above circumstances, the development of a novel waveguide semiconductor photodetector free from the above problems is desirable.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a novel waveguide semiconductor photodetector free from the above problems.
It is a further object of the present invention to provide a novel waveguide semiconductor photodetector with a reduced device resistance, a high performance and a high reliability to a heat generation due to an incidence of a high power light without deterioration and break-down.
The present invention provides a semiconductor device including: a waveguide mesa structure including at least an optical absorption layer for photoelectric conversion; and a heat radiation semiconductor layer in contact directly with at least a part of the optical absorption layer for heat radiation from the optical absorption layer, and the heat radiation semiconductor layer being lower in refractive index and larger in energy band gap than the optical absorption layer.
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T. Takeuchi et al., “A High-Efficiency Waveguide Photodiode for 40-Gb/s Optical Receivers,” Third Optoelectronics and Communications Conference Technical Digest, 1998, Makuhari Messe, pp. 354-355.
Fall 1999; 60thApplied Physical Science 3rdVolume Compilation of Academic Presentations; . 985, 1p-ZC-8 Wave conduction path PD: “Study of resistance to high light input/incidental terminal surface high reliability construction”.
Jackson Jerome
NEC Corporation
Young & Thompson
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