In this paper a Monte Carlo simulator which is focused on the modelling of abrupt heterojunction bipolar transistors (HBTs) is described. In addition, simulation results of an abrupt InP/InGaAs HBT are analysed in order to describe the behaviour of this kind of device, and are compared with experimental data.
A distinctive feature of InP/InGaAs HBTs is their spike-like discontinuity in the E c level at the emitterbase heterojunction interface. The transport of electrons through this potential barrier can be described by the Schr . o odinger's equation. Therefore, in our simulator we have consistently included the numerical solution of this equation in the iterative Monte Carlo procedure.
The simulation results of the transistor include the density of electrons along the device and their velocity, kinetic energy and occupation of the upper conduction sub-bands. It is shown that the electrons in the base region and in the base-collector depletion region are far from thermal equilibrium, and therefore the drift-diffusion transport model is no longer applicable.
Finally, the experimental and simulated Gummel plots J C ðV BE Þ and J B ðV BE Þ are compared in the bias range of common operation of these transistors, showing a good data agreement.