THERMIONIC DIFFUSION-MODEL FOR ABRUPT HBTS INCLUDING SELF-HEATING INSIDE THE MULTILAYER NONPLANAR DEVICE STRUCTURE

A thermo-electrical model which analytically describes the current flo w inside abrupt heterojunction bipolar transistors (HBTs) using thermi onic diffusion theory was developed. This model calculates numerically the three-dimensional temperature distribution inside the multilayer, nonplanar device structure with the help of a semi-analytical approac h. This semi-analytical approach consists of a finite element program computing the heat flow in the mesa structure and an analytical soluti on of the temperature distribution in the substrate. The influence of the nonplanar and multilayer device structure and the effect of metal airbridges on the HBT performance is determined using this model. The phenomenon of thermal runaway in common emitter configuration is expla ined.