The tradeoff between common-emitter current gain (β) and Early voltage (VA) in heterojunction bipolar transistors (HBTs) where the bandgap varies across the base has been studied. The Early voltage depends exponentially on the difference between the bandgap at the collector side of the base and the largest bandgap in the base, allowing very high Early voltages with only very thin narrow bandgap regions. Using Si/Si1-xGex/Si HBTs with a two-layer stepped base, βVA products of over 100,000 V have been achieved for devices with a cutoff frequency expected to be about 30 GHz.
|Original language||English (US)|
|Number of pages||3|
|Journal||Electron device letters|
|State||Published - Dec 1 1991|
All Science Journal Classification (ASJC) codes
- Electrical and Electronic Engineering
- Electronic, Optical and Magnetic Materials