nSi／pSi1—xGex／nSi晶体管直流特性数值分析

采用一维有限差分方法，对生长在Ｓｉ（００１）衬底上的Ｓｉ１－ｘＧｅｘ应变基区异质结双极晶体管（ＨＢＴ）的直流特性进行了数值分析，给出了高斯掺杂情形下，基区中不同Ｇｅ分布的Ｓｉ１－ｘＧｅｘＨＢＴ的共射极电流放大系数图、Ｇｕｍ－ｍｅｌ图和平衡能带图；与Ｓｉ双极同质结晶体管（ＢＪＴ）的直流特性作了对比，结果表明基区中Ｇｅ的引入有效地改善了晶体管的直流性能；其次对基区中Ｇｅ分布与ｐ型杂质在基区－集电区交界处的不一致进行了模拟，证实了基区杂质向集电区扩散产生的寄生势垒使集电极电流密度下降这一实验结果．

Numerical analysis of direct current characteristics of nSi/pSi 1-x Ge x /nSi transistor

The direct current characteristics of Si 1-x Ge x strained base heterojunction bipolar transistor(HBT) are analyzed by 1D limited difference method, whose Si 1-x Ge x strained base is grown on Si(001) substrate. Common emitter current gain, Gummel and equilibrium band diagram of Si 1-x Ge x HBT with Gaussian dopant distribution and different Germanium mole fraction are shown, which are compared with Si bipolar junction transistor. The conclusions show that the direct current characteristics of Si 1-x Ge x HBT are improved effectively due to Germanium. In addition, the nonconsistency between Germanium profile and p type dopant profile near the collector junction is simulated. The results prove that the parasitic barrier caused by dopant outdiffusion from base into collector makes the collector current go down.