Novel GaAs heterojunction bipolar transistors using In/sub 0.5/Al/sub 0.5/P as emitter

We report the fabrication and characterization of the first single and double In/sub 0.5/Al/sub 0.5/P/GaAs heterojunction bipolar transistors (HBT's). These HBT's are grown by gas-source molecular beam epitaxy. The In/sub 0.5/Al/sub 0.5/P/GaAs heterostructure has the largest valence band discontinuity among all Ill-V semiconductor heterojunctions lattice-matched to GaAs. Common-emitter dc current gains as high as 300 and 400 are measured for SHBT's and DHBT's, respectively, with base doping of 1/spl times/10/sup 19/ cm/sup /spl minus/3/. The corresponding offset voltage is 80 and 120 mV, respectively. These results demonstrate the advantages of the In/sub 0.5/Al/sub 0.5/P/GaAs band alignment and make the new HBT's attractive candidates for high-speed digital circuit applications.<
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