Thermal Model of a Heterojunction Bipolar Transistor Taking into Account the Voltage Drop on the Emitter Fingers of Metallization

A thermoelectric model of the structure of a heterojunction bipolar transistor is presented, taking into account a decrease in current density along the emitter metallization paths. To find the temperature field in the transistor structure, the solution of the nonlinear thermal conductivity problem was found by the numerical finite element method, using the COMSOL Multiphysics software environment. Numerical analysis has shown that this effect leads to a strong dependence of the maximum temperature and current density in the structure and the limiting functionality of the device on the topological parameters of the tracks. The results obtained can be used to optimize the design of heterojunction bipolar transistors.