Simulation of the thermal response of self-heating power transistors using a time step adaption method

An implementation of the Rosenbrock-Wanner scheme with embedded time-step adaption in the thermal simulation of AlGaAs-GaAs heterojunction bipolar transistors (HBT) is presented. The simulations are based on discrete 3-D models of the device using the finite integration technique for the solution of the thermal equation. The thermally coupled current response of the device in DC operation is obtained by a nonlinear EM₃ model. Several simulations featuring the thermal crosstalk and the current collapse instability demonstrates the utility of time-step adaption in simulating the alternating slow-fast transients in multifinger HBTs.