Ultra high f/sub max/ InP/InGaAs/InP transferred substrate DHBTs

Very wide bandwidth double heterojunction bipolar transistors (DHBT) will enable high-power amplifiers at 94 and 180 GHz, microwave ADCs, microwave direct digital frequency synthesis, fiber optic transmission at >40 Gb/s and wireless data networks at frequencies above 100 GHz (M. Rodwell et al, IEEE GaAs IC Symp. Tech. Dig., pp. 113-117, 1998). To realize such ICs, transistors with high breakdown voltage, very high current gain cut-off frequency f/sub t/ and very high power gain cut-off frequency f/sub max/ are essential. Transferred substrate single heterojunction bipolar transistors (SHBTs) have demonstrated very high bandwidth and are potential candidates for very high speed integrated circuit applications (Q. Lee et al, IEEE Electron Dev. Lett., vol. 19, pp. 77-79, 1998; Q. Lee et al, ibid., vol. 20, no. 8, pp. 396-398, 1999). The transferred substrate SHBTs, however, have very low breakdown voltage, BV/sub CEO/∼1.5 V. Here we report transferred-substrate DHBTs with emitter junction widths as small as 0.3 μm for the emitter and 1.0 μm for the collector. These exhibit a record 462 GHz f/sub max/.