Title :
The importance of neutral base recombination in compromising the gain of Si/SiGe heterojunction bipolar transistors
Author :
Shafi, Z A ; Gibbings, C.J. ; Ashburn, P. ; Post, I. C R ; Tuppen, C.G. ; Godfrey, D J
Author_Institution :
Dept. of Electron. & Comput. Sci., Southampton Univ., UK
fDate :
8/1/1991 12:00:00 AM
Abstract :
Si/SiGe heterojunction transistors were fabricated with 21.4 nm, heavily doped (5×1019 cm-3) bases. Electrical results from these transistors are presented, and compared with results from comparable silicon homojunction control devices. These results indicate that the collector current is enhanced by a factor of 13, but the potential gain enhancement is compromised by a six-fold increase in base current. The base current is shown to be strongly dependent upon the collector/base voltage, indicating that recombination in the neutral base is the mechanism responsible for the increased base current. The recombination can only be modeled if the lifetime near the collector/base junction is significantly lower than elsewhere in the base. A simple two-region lifetime model predicts a value of 3.0×10-13 s close to the collector-base junction
Keywords :
Ge-Si alloys; carrier lifetime; electron-hole recombination; elemental semiconductors; heterojunction bipolar transistors; silicon; Si-SiGe; base current; collector current; collector/base voltage; heterojunction bipolar transistors; lifetime; neutral base recombination; potential gain enhancement; two-region lifetime model; Bipolar transistors; Capacitance; Flexible printed circuits; Germanium silicon alloys; Heterojunction bipolar transistors; Molecular beam epitaxial growth; Predictive models; Silicon germanium; Switching circuits; Voltage;
Journal_Title :
Electron Devices, IEEE Transactions on
