HBT thermal element design using an electro/thermal simulator

A thermal simulator for radially-symmetric HBTs is described which solves heat conduction equations in cylindrical coordinates. The simulator is coupled to a Poisson-current-continuity equation solver, which also uses cylindrical coordinates, so that we can compute thermal impedances for realistic power distributions. We obtain good agreement between modeled and measured thermal impedances for thermally-shunted HBTs with single emitter dots. We examine about 40 different design cases, allowing us to determine what features of the HBT and thermal design most reduce the thermal impedances. (C) 1998 Elsevier Science Ltd. All rights reserved.