基区非均匀掺杂对　AlGaAs／GaAs　HBT　电学特性影响的数值分析  

Numerical Simulation of Nonuniform Base Doping Effects on Performance of AlGaAs/GaAs HBTs

作　　者：曾峥[1] 吴文刚[1] 罗晋生[1] 

机构地区：[1]西安交通大学电子工程系

出　　处：《Journal of Semiconductors》1994年第12期850-857,共8页半导体学报（英文版）

基　　金：国家教委博士点基金

摘　　要：基于异质结漂移－扩散模型，考虑Ｆｅｒｍｉ－Ｄｉｒａｃ统计和重掺杂能带窄变（ＢＧＮ）效应，对具有非均匀掺杂基区的ＡｌＧａＡｓ／ＧａＡｓＨＢＴ进行了数值模拟．结果表明，当基区非均匀程度较大时，非均匀掺杂引起的基区自建场远大于ＢＧＮ效应产生的反向场．基区非均匀掺杂能提高电流增益，但提高的幅度随非均匀程度的增加而减慢．基区非均匀掺杂可明显改善截止频率ｆＴ，但同时也增加了集电结空间电荷区渡越时间τｃ，ｓｃＲ，使得ｆＴ在非均匀程度较大时开始下降．发射极－集电极ｏｆｆｓｅｔ电压在一定的非均匀程度下达到最佳值．本文还提出了ＡｌＧａＡｓ／ＧａＡｓＨＢＴ基区非均匀掺杂设计的最佳条件．Abstract Numerical simulations of AlGaAs/GaAs HBTs with various base doping gradients were performed. Base doping grading is achieved by varying the doping exponentially from 1 × 1019cm-3 at the base-emitter boundary to NA2 at the basecollector boundary. The inverse built-in field due to bandgap narrowing in the base is far less than the built-in field generated by nonuniform base doping when the nonuniformity is higher. Nonuniform base doping increases the current gain, and this effect will be weakened gradually since the base-emitter SCR recombination current dominates more in the overall base current when the nonuniformity becomes higher. Base doping grading improves the cutoff frequency fT significantly, however,it also increases the base-collector SCR transit time, leading to the fall of ft. when NA2<7.5 × 1017cm-3. Tile offset voltage is improved by nonuniform base doping, and the minimum value can be obtained at NA2= 5 × 1017cm-3. An optimum base grading, NA2= 1 × 1018cm-3, is proposed.

关 键 词：双极晶体管 电学特性 非均匀 掺杂 数值分析 

分 类 号：TN322.8[电子电信—物理电子学]