Sub‐THz Response of Strained‐Silicon MODFETs

Abstract

Plasma waves in gated 2‐D systems can be used to detect THz electromagnetic radiation. This work reports on a two‐dimensional hydrodynamic‐model (HDM) applied to investigate the sub‐THz photovoltaic response of Schottky‐gated strained‐Si MODFETs. TCAD simulation results are validated through comparison with measurements on the transistors. Simulation and experimental results show an excellent agreement in terms of the efficiency of the transconductance. The measurement of the photovoltaic response of s‐Si MOSFETs with 100‐nm gate length is carried out at two sub‐THz frequencies: 0.15 and 0.3 THz. The THz photovoltaic response of the transistor is implemented in TCAD, as in measurements, grounding the source, biasing the gate, and floating the drain contact while a sub‐THz sinusoidal signal is superimposed to the bias gate voltage. In agreement with measurements, a non‐resonant sub‐THz photovoltaic response is found for the simulated devices. As THz detection by any plasma wave FET depends on many parameters (device dimensions, material system, the excitation frequency, etc.), its optimization is a complex problem that needs to be addressed using physics‐based tools, like the HDM. Since the HDM is able to describe in detail the photovoltaic response, its use may be generalized to design plasma wave s‐Si MODFET detectors.