Semiconductor device manufacturing: process – Forming bipolar transistor by formation or alteration of... – Including diode
Reexamination Certificate
2002-07-30
2004-02-10
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Forming bipolar transistor by formation or alteration of...
Including diode
C438S309000
Reexamination Certificate
active
06689667
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to a photoreceiver for detecting and amplifying optical signal in an optical communication system of an ultra-high large-scale wavelength division multiplexing mode, and method of manufacturing the same. More particularly, the invention relates to a photoreceiver in which a photodetector using a quantum-well structure having a quantum confined stark effect as an optical absorption layer and a heterojunction bipolar transistor are integrated on a single chip, whereby an optical signal of a specific wavelength is selectively detected and a converted electrical signal is amplified, thus providing a good amplification characteristic and receiver sensitivity, and method of manufacturing the same.
2. Description of the Prior Art
A conventional photoreceiver, which has been widely used in optical communication systems, has a structure in which a p+InGaAs/i−InGaAs
+InGaAs long wavelength photodetector
10
of a common PiN structure and a heterojunction bipolar transistor
20
of a n+InP/p+InGaAs/i−InGaAs
+InGaAs structure are integrated on a semi-insulating InP substrate
101
, as shown in FIG.
1
.
In other words, the long wavelength photodetector
10
has an n+InGaAs layer
102
A, an n−InGaAs optical absorption layer
103
A and a p+InGaAs ohmic layer
104
A, all of which are stacked on given regions of the semi-insulating InP substrate
101
. At this time, the n−InGaAs optical absorption layer
103
A and the p+InGaAs ohmic layer
104
A are formed on a given region of the n+InGaAs layer
102
A. A p-electrode
105
is formed on a given region of the p+InGaAs ohmic layer
104
A and a n-electrode
106
is also formed on a given region of the n+InGaAs layer
102
A.
Also, a heterojunction bipolar transistor
20
has a n+InGaAs sub-collector
102
B, a n−InGaAs collector
103
B, a p+InGaAs base
104
B, an n+InP emitter
108
and a n+InGaAs ohmic layer
108
, all of which are stacked. The n−InGaAs collector
103
B and the p+InGaAs base
104
B are formed on a given region over the n+InGaAs sub-collector
102
B. An n+InP emitter
107
and an n+InGaAs ohmic layer
108
are also formed on a given region over the p+InGaAs base
104
B. An emitter electrode
109
is formed on the n+InGaAs ohmic layer
108
. A base electrode
110
is formed on a given region over the p+InGaAs base
104
B. A collector electrode
111
is formed on a given region over the n+InGaAs sub-collector
102
B.
Meanwhile, polymer
112
for protecting the surface of the long wavelength photodetector
10
and the heterojunction bipolar transistor
20
and electrically connecting them is formed on the entire structure. The long wavelength photodetector
10
and the heterojunction bipolar transistor
20
are then patterned to expose respective electrodes, thus forming an air bridge metal line between the p-electrode
105
of the photodetector
10
and the base electrode
110
of the heterojunction bipolar transistor
20
.
The crystal structure of the p
+
−InGaAs/i−InGaAs
+
−InGaAs long wavelength photodetector of a simple PiN crystal structure thus constructed, has been widely employed since additional crystal growth for integrated photodetectors are unnecessary because it is same with the base, collector and the sub-collector of the heterojunction bipolar transistor.
The photoreceiver of this structure has only a simple function of detecting and amplifying optical signals but does not have a characteristic of selectively detecting optical signals considering wavelength. Further, there is another problem in the conventional structure. That is, as the layer for absorbing light is the surface incident type, the cross section of an optical fiber is wide and covers all the area of an integrated chip if the structure is made module by using this optical fiber coupling scheme, thus having difficulty in making a module of the structure.
Various wavelengths are multiplexed in a current large-scale wavelength division multiplexing optical communication system. Thus, an optical grating router, an arrangement waveguide diffraction grating, and the like in the receiving element again demultiplexing multiplexed signals. A photodetector then converts the demultiplexed optical signals into electrical signals. Next, an amplifier amplifies the electrical signals. As such, the construction of the receiving elements for demultiplexing, detecting and amplifying the optical signals becomes complex. Therefore, there is a disadvantage that the manufacturing cost is high. Therefore, in order to construct an cost effective optical communication system of a ultra-high long distance large-scale wavelength division-multiplexing mode, there is a need for a photoreceiver for selectively detecting the optical signals of a specific wavelength from various multiplexed wavelengths and having a high gain amplification function of converted electrical signals.
SUMMARY OF THE INVENTION
The present invention is contributed to solve the above problems and an object of the present invention is to provide a single chip integrated photoreceiver capable of selectively detecting optical signals of a specific wavelength from various wavelengths and having a function of amplifying converted electrical signals, and method of manufacturing the same.
Another object of the present invention is to provide a single chip integrated photoreceiver in which a waveguide type photodetector using a quantum-well structure having a quantum confined stark effect as an optical absorption layer and a n+InP/p+InGaAs
−InGaAs
+InGaAsP heterojunction bipolar transistor for amplifying electrical signals converted by the waveguide type photodetector are integrated on semi-insulating InP substrate, and method of manufacturing the same.
According to the present invention, in order to selectively detect optical signals of a specific wavelength, a waveguide type photodetector using a multiple quantum-well layer having a quantum confined stark effect as an optical absorption layer. As shown in
FIG. 2
, the wavelength of light that is absorbed by the quantum confined Stark effect the transition energy of which at the optical absorption band is varied depending on the intensity of an electric field applied to the multiple quantum-well layer, as shown in FIG.
2
. Therefore, a wavelength selective detection characteristic can be very simply implemented. Further, the waveguide type photodetector of this type is integrated on a single semi-insulating InP substrate with a heterojunction bipolar transistor having an n+InP/p+InGaAs
−InGaAs
+InGaAsP high gain amplification characteristic. Therefore, a photoreceiver of a cost effective and high performance having a function of selectively detecting a specific wavelength, which can be used in an optical communication system of a high-performance wavelength division-multiplexing mode, is provided.
In order to accomplish the above object, a photoreceiver according to the present invention, is characterized in that it comprises a waveguide type photodetector consisting of a p+InGaAsP ohmic electrode formed on a given region of a semi-insulating InP substrate, an i−InGaAsP(&lgr;
1
)/i−InGaAsP(&lgr;
2
) optical absorption layer of a multiple quantum-well structure which are stacked on a given region of the p+InGaAsP ohmic electrode, a n+InGaAsP, an n−InGaAs ohmic layer, and a n-electrode and a p-electrode each of which is formed on a given regions of the n−InGaAs layer and a given region of the p+InGaAsP ohmic electrode; and a heterojunction bipolar transistor consisting of a p+InGaAsP layer stacked on a given region of the semi-insulating InP substrate, i−InGaAsP(&lgr;
1
)/i−InGaAsP(&lgr;
2
) layer and n+InGaAsP sub-collector layer of a multiple quantum-well structure, n−InGaAs layer and
Kim Heacheon
Nam Eun soo
Blakely & Sokoloff, Taylor & Zafman
Electronics and Telecommunications Research Institute
Lattin Christopher
Niebling John F.
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