Enhancement of responsivity for a transistor terahertz detector by a Fabry-Pérot resonance-cavity

A method to enhance the responsivity of a transistor terahertz (THz) detector by introducing a Fabry-Perot (FP) cavity was proposed. A theoretical model for the voltage responsivity of the transistor THz detector with a resonant cavity was derived and verified experimentally using a GaN high electron mobility transistor (HEMT) with the FP cavity formed between the GaN HEMT substrate and an indium tin oxide mirror. The measured detector responsivity shows 2.5 times enhancement compared to the device without the cavity and lower noise equivalent power. The performance of the GaN HEMT THz detector with a FP cavity, which has a designed quality factor of 16, is dependent on the incident angle of the THz radiation.