GaAs based heterojunction bipolar transistors have a relatively large turn-on voltage of approximately 1.4 V that can only be decreased by reducing the bandgap energy of the base material. For a variety of applications, particularly operation with low power supply voltage and reduced power dissipation, it would be desirable to have a smaller value of turn-on voltage. We report the DC performance of NpN double heterojunction bipolar transistors fabricated on a GaAs substrate with a Ga0.89I0.11N0.02As0.98-base that has a bandgap energy (E-g) of similar to0.98 eV. These devices have a turn-on voltage V-BE that is 0.4 V lower than that of their GaAs-base counterparts. To overcome the large conduction band discontinuity between GaAs and Ga0.89In0.11N0.02As0.98 both chirped superlattice and delta doping were employed. Peak incremental current gain of h(fe) = 8.5 was obtained. (C) 2002 Elsevier Science Ltd. All rights reserved.