Active solid-state devices (e.g. – transistors – solid-state diode – Heterojunction device – Light responsive structure
Reexamination Certificate
2002-06-14
2004-09-07
Nelms, David (Department: 2818)
Active solid-state devices (e.g., transistors, solid-state diode
Heterojunction device
Light responsive structure
C257S439000
Reexamination Certificate
active
06787818
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to telecommunication transceivers, and more particularly, to a diffused junction photodetector for use in a transceiver and a method of fabricating the same.
BACKGROUND OF THE INVENTION
Telecommunication transceivers are utilized in various applications to transmit and receive communication signals in telecommunication networks. Fiberoptics are used as a transmission medium between the telecommunication transceivers for various transmission reasons including low noise interference, high-speed data transmission rates, and large multiplexing capabilities. In order for the telecommunication transceivers to receive the communication signals transmitted via light over fiberoptic cable, photodetectors are utilized.
Photodetectors transform light energy into electrical energy. Reverse saturation current is controlled by light intensity that shines on the photodetectors. The light generates electron-hole pairs, which induce current. The resulting current is directly proportional to the light intensity.
The use of fiberoptics introduces practical, feasible, and functional requirements. The photodetectors are preferably semiconductor diodes that are inexpensive due to large quantity requirements, reliable, and capable of responding to light signals having wavelengths between 1300 nm and 1600 nm. It is also desirable for the photodetectors to provide low noise or low dark current and be amendable to high volume production.
Commonly used photodetectors are industrially produced and include a germanium (Ge) base or Ge substrate. After formation of the Ge substrate, two general processes are used to form a p-n junction. The first process includes implanting phosphorus or arsenic impurities into the Ge substrate and the second process includes growing epitaxial crystal on the Ge substrate or by implanting phosphorus or arsenic impurities into the Ge substrate as to create a p-n junction. The above-mentioned processes, as known in the art, are expensive, time consuming, complex, and have a high defect rate. The Ge substrate post formation doping of impurities to form a p-n junction is highly susceptible to forming defects due to inherent nature of the post formation process.
It would therefore be desirable to develop a photodetector that provides low noise and is capable of responding to wavelengths between 1300 nm and 1600 nm. It would also be desirable to develop a process for fabricating the desired photodetector that is inexpensive, less time consuming to produce, less complex, and has a low defect rate.
SUMMARY OF THE INVENTION
The present invention provides a method and apparatus for a diffused junction photodetector for use in a transceiver and a method of fabricating the same. A diffused junction semiconductor for detecting light at a predetermined wavelength is provided including a base and an epitaxial structure electrically coupled to the base. The epitaxial structure forms a p-n junction in the base. The epitaxial structure includes at least one diffusion layer electrically coupled to the base. At least one of the diffusion layers contributes impurities in at least a portion of the base to form the p-n junction during growth of the epitaxial structure. A method for performing the same is also provided.
One of several advantages of the present invention is the ability to diffuse impurities into the base during growth of the epitaxial structure. In so doing, a p-n junction may be formed within a semiconductor using a relatively inexpensive technique and in a relatively short period of time as compared with traditional techniques. The inexpensive technique includes use of large area substrates in conjunction with a multi-layer wafer production metal organic vapor phase epitaxy (MOVPE) reactor.
Another advantage of the present invention is the ability to provide a semiconductor with low leakage current due to passivation of a wide bandgap semiconductor around the p-n junction, application of an anti-reflective coating over the epitaxial structure, and carrier concentration in the base.
Furthermore, the present invention provides application versatility in that resistivity of various layers of the substrate may be modified, thereby, adjusting various semiconductor parameters.
Other advantages and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.
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Boisvert Joseph C.
Haddad Moran
Karam Nasser H.
King Richard R.
Krut Dimitri
Gudmestad Terje
Ho Tu-Tu
The Boeing Company
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