Characteristics of submicron HBTs in the 140-220 GHz band

Reports the measurement of submicron transferred-substrate InGaAs/InAlAs heterojunction bipolar transistors (HBTs) in the 140-220 GHz frequency band. We believe this is the first reported characterization of HBTs above 110 GHz. Previous measurements of transferred-substrate HBTs have predicted record values of power gain cutoff frequency by extrapolating at -20 dB/decade the unilateral power gain measured at 110 GHz. Due to uncertainties associated with our measurement techniques, the unilateral power gain could not be determined for higher-gain devices. Additionally, transistor S-parameters measured in the 140-220 GHz band do not correlate well with a hybrid-pi model derived from measurements at lower (6-45 GHz) frequencies.