按比例缩小SiGe HBT能量传输模型

针对用传统的漂移扩散模型分析小尺寸SiGe HBT的局限性,采用新的能量传输模型.通过分析建立了小尺寸SiGe HBT(考虑Ge含量)的玻尔兹曼方程,得到不同区域电子温度的分布;并比较了不同基区宽度、不同Ge梯度下的电子温度曲线.结果发现在基区很薄的情况下,电子从基区向集电区渡越时,其温度逐渐升高,且大大高于晶格温度,且不同基区宽度基区电子温度变化率不同.

Energy Transport Model of Scaling SiGe HBT

The model of SiGe HBT(heterojunction bipolar transistor) based on simplified energy transport equation is given and the exact solution of this equation is obtained,from which exact distributions of electron temperature in different regions of the miniature SiGe HBT can be seen.Firstly,the four chapters are as follows: Aiming at electric field distribution in the base and C-B junction,different methods are applied to the three subregions:neutral base,the base part of B-C junction and the collector part of B-C junction.Expressions of electric field are then obtained when assuming boron doping in the base is gaussian and germanium doping is linear.In addition,Ge-induced bandgap narrowing is considered.Secondly,built-in potential,neutral base width W_(Beff) and collector depletion width W_(dc) have been derived,then Boltzmann transport equation is founded taking into account Ge content influence.According to the boundary condition,different electron temperature distributions in different regions can be described.Exact solutions of these equations are obtained.Thirdly,the electron temperature curves under different base widths are given and those under different Ge gradients are compared.During their transitions,electron temperatures surpass by far the lattice temperature 300K.Maximum point of electron temperature can be expressed.Finally,the(foundation) for analyzing velocity overshoot effect is laid in(future) bipolar transistor.