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US 6,784,450 B2Granted
Graded base GaAsSb for high speed GaAs HBT
AssigneeMicroLink Devices, Inc.
InventorsNoren Pan, Byung-Kwon Han
Life of this patent
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Abstract
A heterojunction bipolar transistor is provided having an improved current gain cutoff frequency. The heterojunction bipolar transistor includes a graded base layer formed from antimony. The graded base allows the heterojunction bipolar transistor to establish a quasi-electric field to yield an improved cutoff frequency.
Claims16
A heterojunction bipolar transistor, comprising
- a collector layer disposed on a substrate to form a first stack,
- a graded base layer having a gradually varied composition disposed on a portion of the collector layer to form a second stack,
- an emitter layer disposed on a portion of the base layer to form a third stack, and
- a contact layer disposed on a portion of the emitter layer to form a fourth stack, wherein an impurity concentration within the graded base layer gradually increases from a first surface of the graded base layer adjacent a layer of the first stack to a second surface of the graded base layer adjacent a layer of the third stack within the heterojunction bipolar transistor to allow the heterojunction bipolar transistor to generate an energy gradient of a sufficient value to realize a current gain cutoff frequency (fT) in excess of 100 GHz.
1 more element
Dependencies are inferred from the claim text.