Detection of output power from sub-THz InP-based resonant tunneling diode oscillator using Ni-InP Schottky barrier diode

We report on direct and heterodyne detection of output power from InP-based resonant tunneling diode (RTD) oscillator in sub-THz range using InP Schottky barrier diode (SBD). The SBD is Ni-InP and integrated with bow-tie antenna. In the 2nd harmonic heterodyne detection, the spectral linewidth was measured to be 3 and 10 MHz for RTDs oscillating at 373 and 550 GHz, respectively. Measured linewidths were in reasonable agreement with theoretical calculations, in which the linewidth is inversely proportional to output power and square of the Q value of the resonator. Narrow linewidth can be obtained with a device having high output power and Q value. Frequency change with bias voltage of RTD oscillator was also measured accurately, which is useful for phase-locked loop system.