Теплоэлектрическая модель гетеропереходного биполярного транзистора с учетом падения напряжения на сопротивлении токоведущей металлизации

Abstract

A 3D thermoelectric model has been developed to calculate the temperature field in the comb structure of a heterojunction bipolar transistor formed on the surface of a rectangular semiconductor crystal with the length of the emitter metallization paths comparable to the size of the crystal, taking into account the inhomogeneous distribution of current density under the emitter paths due to voltage drop on the resistance of current-carrying metallization. The model is based on the solution of the thermal conductivity equation together with a system of equations for the distribution of the potential for metallization of the emitter track and the current density under the track in the COMSOL Multiphysics software environment. It is shown that as a result of the combined effect of the voltage drop on the resistances of the emitter tracks, the inhomogeneity of the temperature field in a crystal with limited dimensions and the strong dependence of the emitter current density on temperature, the temperature and current density distributions along the emitter tracks change character: from monotonously and weakly decreasing from the beginning of the track to the end in the isothermal approximation, these distributions become non-monotonic and significantly heterogeneous. At the same time, the maximum current density and temperature with an increase in the operating current shifts from the beginning to the center of the tracks. It has also been found that with the crystal sizes unchanged, an increase in the length of the tracks leads to a certain decrease in the coefficient of inhomogeneity of the temperature distribution.