【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,特别是在低温下更为严重更多还原

【Abstract】 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.更多还原