AlGaAs/GaAs HBTs: an ultra sensitive decision circuit for a 10 Gbps optical communication system

The authors report on a high-performance AlGaAs/GaAs HBT (heterojunction bipolar transistor) decision circuit for a 10-GB/s optical communication receiver. Using HBTs whose f_max was 90 GHz at a standard operations bias point in the circuit, an ultrasensitive decision ambiguity width of 7 mV_p-p and a wide phase margin of 280° at a data rate of 10 Gb/s were obtained. Resulting from precisely controlled molecular-beam-epitaxy growth and elaborate fabrication processes, the HBTs were endowed with large h_FE, f_T , and f_max of 50, 50 GHz, and 90 GHz, respectively, under the standard operation bias point in the circuit. The results obtained indicate the superiority of AlGaAs/GaAs HBTs for future ultrahigh-speed digital systems