InP/GaAsSb/InP double heterojunction bipolar transistor structures were grown in a solid-source molecular beam epitaxy system. Carbon or Be was used for the p-type doping of GaAs0.51Sb0.49. Hole concentrations in excess 2 x 10(20) cm(-3) were obtained in carbon doped GaAs0.51Sb0.49 films. InP/GaAsSb/InP double heterojunction bipolar transistors were fabricated as wet-etched triple mesa structures. Common-emitter current gain, beta, > 80 was measured for large area devices with 20 x 20 pm 2 emitter geometry, and a base doping of 1 X 10(19) cm(-3). BVCEO > 6 V was measured for devices incorporating a 2000 Angstrom thick InP collector. The gain of the transistor decreased to 20 as the base doping level was increased to 5 x 10(19) cm(-3). (C) 2002 Elsevier Science B.V. All rights reserved.