A high-performance InGaAs/InAlAs double-heterojunction bipolar transistor with nonalloyed n/sup +/-InAs cap layer on InP(n) grown by molecular beam epitaxy

An InGaAs/InAlAs double-heterojunction bipolar transistor (DHBT) on InP(n) grown by molecular-beam epitaxy (MBE) that exhibits high DC performance is discussed. An n/sup +/-InAs emitter cap layer was used for nonalloyed contacts in the structure and specific contact resistances of 1.8*10/sup -7/ and 6.0*10/sup -6/ Omega -cm/sup 2/ were measured for the nonalloyed emitter and base contacts, respectively. Since no high-temperature annealing is necessary, excellent contact surface morphology on thinner base devices can easily be obtained. In devices with 50*50- mu m/sup 2/ emitter area, common-emitter current gains as high as 1500 were achieved at a collector current density of 2.7*10/sup 3/ A/cm/sup 2/. The current gain increased up to 2000 for alloyed devices.<
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