GaN/InGaN heterojunction bipolar transistors (HBTs) are very promising for high speed, high power density applications at elevated temperatures. In this paper we report on simulations of the de performance of GaN/In0.2Ga0.8N HBTs as a function of the layer design and doping levels. The conductivity of p-InGaN is significantly lower than p-GaN, reducing the deleterious effects of high ohmic contact resistance. Predicted dc current gains are given as a function of base doping and thickness and are in excess of several hundred even for aggressive layer designs. Advantages with respect to GaN base HBTs are also discussed. (C) 2003 Elsevier Science Ltd. All rights reserved.