Investigation of the burn-in effect in microwave GaInP/GaAs HBTs by means of numerical simulations

GaInP/GaAs HBTs demonstrate outstanding long-term reliability performance. Nevertheless they still suffer from a short-term DC current gain instability, known as the burn-in effect. Even if the effect is usually attributed to hydrogen contamination passivating the carbon atoms employed as base dopant, the underlying physical mechanism is still unclear. The present work addresses the burn-in effect by means of numerical simulations performed with the device simulation software BLAZE by Silvaco. The results give support to the hypothesis that the burn-in effect is a surface related phenomenon. The simulations reveal that a fixed surface charge located near the edge of the emitter mesa should be introduced. The work points out also that simultaneous variations of both this charge and of the surface recombination velocity should be taken into account. This simulation approach could be a useful tool, in order to develop a chemical/physical model of the burn-in effect.