摘要
由于发射结(EB结)价带存在着能量差ΔEv,电流增益β不再主要由发射区和基区杂质浓度比来决定,给HBT设计带来了更大的自由度。为减小基区电阻和防止低温载流子冻析,可增加基区浓度。但基区重掺杂导致禁带变窄,禁带变窄的非均匀性产生的阻滞电场使基区渡越时间增加,退化了频率特性。
The presence of valance bandgap discontinuity, Δ E v, at BE heterojunction gives greater design freedom for HBT’s, compared with BJT’s, because current gain is not determined mainly by the concentration ratio of the emitter to base.In order to reduce base resistance and mitigate carrier freeze out at low temperatures, the base concentration can be increased. However, the retarding field due to the nonuniform heavy doping bandgap narrowing increases base transit time, which degrades frequency performance, especially at low temperatures.
出处
《微电子学》
CAS
CSCD
北大核心
2000年第1期5-7,共3页
Microelectronics
基金
北京市自然科学基金
北京市科技新星计划
电子元器件可靠性国家重点实验室资助课题
关键词
异质结晶体管
掺杂
基区渡越时间
硅
锗化硅
HBT
Heterojunctio transistor
Base Transit Time
Semiconductor physics
Doping
Si Ge device
