Claims
- 1. A heterojunction bipolar transistor comprising:
- an emitter layer of a first conductivity type;
- a base layer of a second conductivity type adjacent to said emitter layer;
- a collector buffer layer of the first conductivity type; and
- a collector layer arranged between said collector buffer layer and said base layer,
- wherein said collector layer includes a first collector sub-layer formed at the side of said base layer and a second collector sub-layer arranged at the side of said collector buffer layer,
- said first collector sub-layer is a semiconductor layer having an impurity concentration lower than that of said base layer, and
- said second collector sub-layer is a semiconductor layer of the second conductivity type having an impurity concentration higher than that of said first collector sub-layer,
- wherein said first collector sub-layer and said second collector sub-layer are depleted in an operating state and form an electric field distribution determined by parameters of said base layer, said first collector sub-layer, said second collector sub-layer and said collector buffer layer.
- 2. A transistor according to claim 1, wherein said collector buffer layer is a collector electrode layer.
- 3. A transistor according to claim 1, wherein said first collector sub-layer is the first conductivity type and its impurity concentration is designed so that the impurity concentration compensates for a space charge produced by free carriers injected into the collector depletion layer upon transistor operation.
- 4. A transistor according to claim 1, further comprising a third collector sub-layer between said base layer and said first collector sub-layer,
- wherein said third collector sub-layer is the first conductivity type, and
- wherein said first, said second and said third collector sub-layers are depleted in an operating state and form an electric field distribution determined by parameters of said base layer, said first, said second, said third collector sub-layers and said collector buffer layer.
- 5. A heterojunction bipolar transistor comprising:
- an emitter layer of a first conductivity type;
- a base layer of a second conductivity type adjacent to said emitter layer;
- a collector buffer layer of the first conductivity type; and
- a collector layer arranged between said collector buffer layer and said base layer,
- wherein said collector layer includes a first collector sub-layer formed at the side of said base layer and a second collector sub-layer arranged at the side of said collector buffer layer,
- said first collector sub-layer is a semiconductor layer having an impurity concentration lower than that of said collector buffer layer, a band gap energy of which is formed in a predetermined distribution from said base layer to said second collector sub-layer,
- said second collector sub-layer is a semiconductor layer of the second conductivity type having an impurity concentration higher than that of said first collector sub-layer, a band gap energy which is formed in a predetermined distribution from said first collector sub-layer to said collector buffer layer, and
- said collector buffer layer has a band gap energy larger than that of said second collector sub-layer,
- wherein said first collector sub-layer and second collector sub-layer are depleted in an operating state and form an electric field distribution determined by parameters of said base layer, said first collector sub-layer, said second collector sub-layer and said collector buffer layer.
- 6. A transistor according to claim 5, wherein the band gap energy of said first collector sub-layer is increasing from said base layer to said collector buffer layer.
- 7. A transistor according to claim 5, wherein distribution of the band gap energy of said first collector sub-layer and distribution of said second collector sub-layer form a pattern which is gradually increased as a whole.
Priority Claims (2)
Number |
Date |
Country |
Kind |
62-24761 |
Feb 1987 |
JPX |
|
62-125748 |
May 1987 |
JPX |
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Parent Case Info
This is a continuation of application Ser. No. 152,899, filed Feb. 5, 1988, now abandoned.
US Referenced Citations (1)
Number |
Name |
Date |
Kind |
4672413 |
Gardner |
Jun 1987 |
|
Foreign Referenced Citations (2)
Number |
Date |
Country |
62-12164 |
Jan 1987 |
JPX |
62-33461 |
Feb 1987 |
JPX |
Non-Patent Literature Citations (1)
Entry |
"A Proposed Structure for Collector Transit-Time Reduction in AlGaAs/GaAs Bipolar Transistors" by C. M. Maziar et al. (IEEE, Electron Dev. Lett. EDL-7, No. 8, pp. 483-485, 1986). |
Continuations (1)
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Number |
Date |
Country |
Parent |
152899 |
Feb 1988 |
|