Enhanced Terahertz Detection in Resonant Tunnel Diode-Gated HEMTs

Abstract

We report our studies on terahertz detection in high electron mobility transistors (HEMTs) with a resonant-tunneling gate structure, which exhibits negative differential conductance (NDC) from gate to channel; namely, resonant-tunnel-diode (RTD) gated HEMTs. The effect of NDC on detector responsivity is theoretically derived based on Dyakonov-Shur electron-plasma wave theory. The positive gate conductance in traditional HEMTs damps the electron plasma waves, therefore reducing responsivity; conversely, in devices employing NDC gates, detector sensitivity can be greatly enhanced. Our analysis also demonstrates that resonant detection, thus high responsivity, can be obtained even near the threshold voltage in RTD-gated HEMTs, while only non-resonant detection is attainable in conventional HEMTs in this bias regime. Numerical exploration of the design space for GaN HEMTs with double-barrier AlGaN/GaN/AlGaN RTD gates is performed, showing that thin barriers with low Al composition may be the most practical structures to demonstrate this enhanced detection mechanism.