Authors: F. Dhondt, J. Barrette, P.A. Rolland and S. Delage
Affilation: IEMN, France
Pages: 105 - 110
Keywords: electrothermal model, numerical reduction, heat flow equation
We present a 3-D electrothermal model based on the finite difference method and applied to GaAs heterojunction bipolar transistors (HBTs). This non-linear model compmes the temperature distribution under static bias conditions for multifinger HBTs, although it can be modified to simulate silicon bipolar devices. The model takes into account emitter ballast resistance, thermal shunt design and the non-linear temperature dependence of substrate thermal conductivity. A simplified analytic electrical model for the BT can be modified to fit the userts device characteristics. We compute maximum junction temperature and device thermal resistance for three dimensional BT structures. We use this model to aptimize the thermal design of InGaP/GaAs BTs employing emitter ballast resistance and thermal shunt, and we compare the parallel topology to the distributed (or "fishbone") topology for power HBT unit cells.