Title :
Current gain-Early voltage products in heterojunction bipolar transistors with nonuniform base bandgaps
Author :
Prinz, E.J. ; Sturm, James C.
Author_Institution :
Dept. of Electr. Eng., Princeton Univ., NJ, USA
Abstract :
The tradeoff between common-emitter current gain ( beta ) and Early voltage (V/sub A/) 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/Si/sub 1-x/Ge/sub x//Si HBTs with a two-layer stepped base, beta V/sub A/ products of over 100000 V have been achieved for devices with a cutoff frequency expected to be about 30 GHz.<>
Keywords :
Ge-Si alloys; energy gap; heterojunction bipolar transistors; semiconductor device models; semiconductor junctions; silicon; solid-state microwave devices; 30 GHz; Early voltage; HBTs; Si-Si/sub 1-x/Ge/sub x/-Si; bandgap varies; bandgap varies across base; common-emitter current gain; current voltage Early voltage products; cutoff frequency; heterojunction bipolar transistors; nonuniform base bandgaps; thin narrow bandgap regions; two-layer stepped base; Analog circuits; Bipolar transistors; Capacitance; Control theory; Current density; Cutoff frequency; Digital circuits; Heterojunction bipolar transistors; Photonic band gap; Voltage;
Journal_Title :
Electron Device Letters, IEEE
