Optimization of THz response of strained‐Si MODFETs

Abstract

This paper reports on the study of strained‐Si n‐channel MODFETs as detectors of sub‐THz radiation. Simulations based on a bi‐dimensional hydrodynamic model for the charge transport coupled to a Poisson equation solver were performed. A charge boundary condition for the floating drain contact was implemented to obtain the photovoltaic response of the device. Time‐domain simulations were performed to generate the stationary time series needed to obtain the photovoltaic response. A non‐resonant THz photo‐response was obtained in agreement with experimental results and theoretical works on plasma waves devices. It was found that the photovoltaic response of s‐Si MODFETs with non self‐aligned gates is strongly influenced by both gate's length and topology. In particular, it was demonstrated that at frequencies around 0.3 THz a double‐finger gate delivers a stronger PV response than a conventional single‐finger gate structure. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Sub-THz Imaging Using Non-Resonant HEMT Detectors

“…In Section 3 results are presented: DC and low frequency AC characteristics show an excellent agreement between experimental and simulation results serving as a validation of the TCAD model developed. Also, a qualitative agreement was found when comparing TCAD results with measurements; both show a broadband detection of the THz radiation previously found in T-gate Si/Ge FETs [ 29 , 30 , 31 ]. Responsivity and NEP (Noise Equivalent Power) were obtained in the photovoltaic mode.…”

“…The paper is organized as follows: In Section 2 the Si/SiGe MODFET, along with its geometry and epilayer description, is presented; detection of sub-THz [ 29 , 30 ] and imaging using Si/SiGe transistors were already demonstrated [ 31 ]. The physics-based TCAD tool based on the method of moments used to simulate the transistor is subsequently presented.…”

Room-Temperature Terahertz Detection and Imaging by Using Strained-Silicon MODFETs

“…It is related to over-damping of the plasma waves in the channel where the AC current generated by the incoming radiation at the source cannot reach the drain side of the channel. A theoretical study of the photoresponse in this regime is presented in [21,22]. The quality factor [19] is given by: Q = ωτ, where τ is the relaxation time given by m * μ/e (m * : the electron effective mass, μ: the electron mobility, and e: the absolute value of the electron charge).…”

“…This chapter presents a study of room-temperature terahertz detection using strained-silicon modulation field-effect transistors with three different gate lengths. Detection of THz radiation [21,22] and imaging using Si/SiGe transistors have been previously demonstrated [23,24]. A main distinct interest of the high-mobility n-type FETs based on the Si/SiGe system is that, unlike the ones based on III-V plasmon detectors, it will be easy to integrate MODFET THz detectors with mainstream Si technology circuits, since both are fabricated on conventional…”