Type-II GaAsSb/InP DHBTs With Record fT = 670 GHz and Simultaneous fT, fMAX > 400 GHz

[[abstract]]InP/GaAsSb/InP DHBTs with 125 and 150 nm collector thicknesses were fabricated by optical contact lithography in a standard triple mesa process. It is shown that a peak current-gain cut-off frequency fT = 343 GHz and maximum oscillation frequency fMAX = 351 GHz were simultaneously achieved on devices with an emitter area of 0.6 × 11.5 m2 and a 150 nm collector. To the best of our knowledge, these are the first InP/GaAsSb DHBTs to offer balanced figures-of-merit exceeding 300 GHz and a current gain > 60. Similar devices with a thinner collector (125 nm) exhibit a peak fT = 377 GHz with fMAX = 318 GHz due to the interplay between a reduced collector transit time and the increased collector-base depletion capacitance. For the devices under study, the extrinsic collector-base capacitance was observed to have a small impact on fMAX. However, the base mesa over-etching is essential to reduce the extrinsic capacitance and thus improve fT.[[fileno]]2030161030008[[department]]電機工程學