High-sensitivity differential terahertz detector based on antenna-coupled InP high-electron-mobility transistors

We report an approach for enhancing the sensitivity of terahertz detectors based on self-mixing in antenna-coupled field-effect transistors, and verify that such sensitivity can be significantly enhanced by adopting a differential detector design, enhancing electron mobility, reducing ohmic contact resistance, and minimizing surface roughness. Using this approach, a room-temperature optical noise-equivalent power (NEP) of 7.7pW/Hz at 363.7 GHz was achieved in an antenna-coupled differential InP high-electron-mobility transistor (HEMT) detector with a 2-μm gate length, fabricated exclusively via contact lithography. This performance is comparable to that of state-of-the-art CMOS and GaN HEMT terahertz detectors with deep-submicron gate lengths. This result indicates that further scaling the gate length of the InP HEMT detector down to the deep-submicron regime is expected to break the sensitivity limit and reduce the optical NEP to the sub-pW/Hz level at room temperature.