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US 5,631,477 AGranted
Quaternary collector InAlAs-InGaAlAs heterojunction bipolar transistor
AssigneeTRW Inc.
InventorsDwight C. Streit, Aaron K. Oki, Liem T. Tran
Life of this patent
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Abstract
An InAlAs/InGaAlAs heterojunction bipolar transistor that includes a constant quaternary InGaAlAs collector layer. Graded InGaAlAs collector layers are provided on each side of the quaternary collector layer to minimize transitions through the constant collector layer. The InAlAs/InGaAlAs HBT may also include one or more of a graded InGaAlAs emitter-base transition region, a graded-doping InGaAs base layer, and a graded-composition InGaAlAs base layer.
Claims17
A semiconductor device comprising:
- a substrate;
- an InGaAlAs collector layer positioned on the substrate, said collector layer having a substantially constant composition of InGaAlAs;
- a base layer positioned on the collector layer;
- a first graded InGaAlAs layer positioned between the collector layer and the substrate and a second InGaAlAs graded layer positioned between the collector layer and the base layer, wherein the first and second graded layers include graded aluminum such that the concentration of aluminum of the first graded layer at a surface of the first graded layer opposite to the collector layer is substantially zero and the concentration of aluminum of the first graded layer at a surface of the first graded layer adjacent to the collector layer is substantially the same as the concentration of aluminum in the collector layer, and wherein the concentration of aluminum of the second graded layer at a surface of the second graded layer adjacent to the base layer is nearly zero and the concentration of aluminum of the second graded layer at a surface of the second graded layer adjacent to the collector layer is substantially the same as the concentration of aluminum in the collector layer;
- a graded InGaAlAs emitter-base transition layer positioned on the base layer;
- and
- an emitter layer positioned on the emitter-base transition layer, wherein the graded transition layer has a graded composition so as to have substantially the same composition as the base layer at a surface adjacent to the base layer and substantially the same composition as the emitter layer at a surface adjacent to the emitter layer.
4 more elements
A semiconductor device comprising:
- a substrate;
- an InGaAlAs collector layer positioned on the substrate, said collector layer having a substantially constant composition of InGaAlAs;
- a base layer positioned on the collector layer, said base layer including a p-type graded doping profile having a first doping concentration at a surface of the base layer closest to the collector layer and a second doping concentration at a surface of the base layer proximate to an emitter layer, wherein the base layer doping profile is graded so that the first doping concentration is less than the second doping concentration;
- and
- a first graded InGaAlAs layer positioned between the collector layer and the substrate and a second InGaAlAs graded layer positioned between the collector layer and the base layer, wherein the first and second graded layers include graded aluminum such that the concentration of aluminum of the first graded layer at a surface of the first graded layer opposite to the collector layer is substantially zero and the concentration of aluminum of the first graded layer at a surface of the first graded layer adjacent to the collector layer is substantially the same as the concentration of aluminum in the collector layer, and wherein the concentration of aluminum of the second graded layer at a surface of the second graded layer adjacent to the base layer is nearly zero and the concentration of aluminum of the second graded layer at a surface of the second graded layer adjacent to the collector layer is substantially the same as the concentration of aluminum in the collector layer.
2 more elements
A semiconductor device comprising:
- a substrate;
- an InGaAlAs collector layer positioned on the substrate;
- an InGaAlAs base layer positioned on the collector layer;
- and
- an InAlAs emitter layer positioned on the base layer, wherein the base layer is a graded composition base layer such that the base layer has its highest concentration of Ga closest to the collector layer and has its lowest concentration of Ga closest to the emitter layer and its lowest concentration of Al closest to the collector layer and its highest concentration of Al closest to the emitter layer.
2 more elements
Dependencies are inferred from the claim text.