P-n-p In0.52 Al0.48 As/In0.53 Ga0.47 As double-heterojunction bipolar transistors (DHBT's) with a p+-InAs emitter cap layer grown by molecular beam epitaxy (MBE) have been realized and tested for the first time. A five-period 15-Å-thick In0.53 Ga0.47 As/InAs superlattice was incorporated between the In0.53 Ga0.47 As and InAs cap layer to smooth out the valence-band discontinuity. Specific contact resistances of 1 x 10-5 and 2 x 10-6 Ω.cm2 were measured for nonalloyed emitter and base contacts, respectively. A maximum common emitter current gain of 70 has been measured for a 1500- Å -thick base transistor at a collector current density of 1.2 X 103 A/cm2. Typical current gains of devices with 50 x 50-μm2 emitter areas were around 50 with ideality factors of 1.4.