PNP型SiGe HBT的电流增益与Ge组分研究

Study on the Current Gain in PNP SiGe HBT and Ge-profile

在进行PNP型SiGe HBT的设计时,通过改变Ge组分而改变能带结构,而获得较高的电流增益。文章对基区中的Ge组分分布三种形式:三角形、梯形、矩形进行计算机模拟并进行结果分析,认为其它条件相同时,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,本文从能带结构和势垒角度对此进行讨论。

When people design the physical structure of PNP SiGe HBT,they can pursue higher value of βthrough changingthe band-gap structure of it.There are generally three types of Ge-profile in base:triangle-Profile,trapezium-Profile and rect-angle-Profile.In this paper,we model and simulate the devices of PNP SiGe HBT with the three types of Ge-profile respective-ly and compare the results and explain and discuss them fur-ther.Trapezium-Profile gets the highest value of them.And the pluses of both trapezium-Profile and triangle-Profile rise with the increase of Ge contents,while rectangle-Profile begins to decline at some point.