Smaller Antenna-Gate Gap For Higher Sensitivity Of Gan/Algan Hemt Terahertz Detectors

We report an attempt to improve the sensitivity of terahertz detection based on self-mixing in antenna-coupled field-effect transistors by enhancing the field-effect factor and the antenna factor with a reduced gate length and a reduced antenna-gate gap, respectively. An optical noise equivalent power (NEP) of 3.7pW/Hz at 0.65THz was achieved in a GaN/AlGaN high-electron-mobility transistor (HEMT) with a gate length of 300nm and an antenna-gate gap of 200nm at room temperature. It was found that the antenna factor was inversely proportional to the antenna-gate gap, and the responses upon coherent/incoherent terahertz irradiation were well described by the self-mixing model. To fill the NEP gap of 0.1-1pW/Hz between room-temperature and cryogenic detectors by HEMT-based detectors at room temperature, impedance match needs to be carefully considered.