Thermal impact of InGaAs on InP based HBTs

Thermal characteristics of typical InP/InGaAs and InGaP/GaAs HBTs were compared by simulation. Parameters such as emitter dimensions, number of emitters, emitter pitch, and thickness of device layers were varied over ranges of interest. Despite the higher thermal conductivity of the InP substrate compared to GaAs, thermal resistance of InP/InGaAs HBTs was generally higher than that of comparable InGaP/GaAs HBTs because of the very low thermal conductivity of InGaAs. Approaches for minimizing this adverse effect are discussed.