In/sub 0.52/Al/sub 0.48/As/In/sub 0.53/Ga/sub 0.47/As double-heterojunction p-n-p bipolar transistors grown by molecular beam epitaxy

P-n-p In/sub 0.52/Al/sub 0.48/As/In/sub 0.53/Ga/sub 0.47/As double-heterojunction bipolar transistors with a p/sup +/-InAs emitter cap layer grown by molecular-beam epitaxy have been realized and tested. A five-period 15-AA-thick In/sub 0.53/Ga/sub 0.47/As/InAs superlattice was incorporated between the In/sub 0.53/Ga/sub 0.47/As and InAs cap layer to smooth out the valence-band discontinuity. Specific contact resistance of 1*10/sup -5/ and 2*10/sup -6/ Omega -cm/sup 2/ were measured for nonalloyed emitter and base contacts, respectively. A maximum common emitter current gain of 70 has been measured for a 1500-AA-thick base transistor at a collector current density of 1.2*10/sup 3/ A/cm/sup 2/. Typical current gains of devices with 50*50- mu m/sup 2/ emitter areas were around 50 with ideality factors of 1.4.<
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