GaAs0.5Sb0.5/InP UTC-PD with graded-bandgap collector for zero-bias operation at sub-THz regime

By using type-II absorption-collector interface and graded-bandgap collector in UTC-PDs for zero-bias operation, such photodiode achieves record 3-dB O-E bandwidth (140 GHz) and sub-THz output power (-13.9dBm at 160GHz) among all the reported zero-bias photodiodes.