pnp型SiGe HBT特性与Ge组分分布的相关性

Intercoordination between the characteristics of pnp SiGe HBT with the Ge-profile

在进行pnp型SiGe HBT的设计时,通过改变基区Ge组分改变能带结构,从而获得较高的电流增益和截止频率。本文就基区中Ge组分分布的三种形式:三角形、梯形、矩形进行计算机模拟并对结果进行讨论,发现其他条件相同时,梯形分布的pnp SiGe HBT的放大系数最大,而且梯形和三角形随Ge组分的增大而增大,但是矩形分布在Ge组分增大到一定数值后开始减小,而特征频率情况类似。

When designing the physical structure of pnp SiGe HBT,the higher value ofβand f T can be obtained through changing the Ge composition in base to vary the band-gap structure of it.There are generally three types of Ge-profile in base:triangle-profile,trapezium-profile and rectangle-profile.In this paper,we model and simulate the devices of pnp SiGe HBT with the three types of Ge-profile respectively and compare the results and explain and discuss them fur-ther.Trapezium-profile gets the highest value of them.And the amplification factors of both trapezium-profile and triangle-profile rise with the increase of Ge contents,and rectangle-profile begins to decline at some points,while the values of eigenfrequency are similar.