Multi-Segment TFT Compact Model for THz Applications.

Xueqing Liu,Michael Shur,Trond Ytterdal

doi:10.3390/nano12050765

Abstract

We present an update of the Rensselaer Polytechnic Institute (RPI) thin-film transistor (TFT) compact model. The updated model implemented in Simulation Program with Integrated Circuit Emphasis (SPICE) accounts for the gate voltage-dependent channel layer thickness, enables the accurate description of the direct current (DC) characteristics, and uses channel segmentation to allow for terahertz (THz) frequency simulations. The model introduces two subthreshold ideality factors to describe the control of the gate voltage on the channel layer and its effect on the drain-to-source current and the channel capacitance. The calculated field distribution in the channel is used to evaluate the channel segment parameters including the segment impedance, kinetic inductance, and gate-to-segment capacitances. Our approach reproduces the conventional RPI TFT model at low frequencies, fits the measured current–voltage characteristics with sufficient accuracy, and extends the RPI TFT model applications into the THz frequency range. Our calculations show that a single TFT or complementary TFTs could efficiently detect the sub-terahertz and terahertz radiation.

Highlights

Thin-film transistor (TFT) technology has found numerous applications including large area and flexible displays [1,2], sensitive skin [3], biomedical and chemical sensors [4], and radio frequency identification (RFID) sensors [5]
The emergence of novel TFT materials such as ZnO [7,8], InGaZnO [9], carbon nanotube (CNT) [10], and organic materials [11] has been improving the properties of TFTs including the carrier mobility, current-carrying capacities, stability, and mechanical flexibility
The conventional Rensselaer Polytechnic Institute (RPI) TFT model does not account for the dependence of the channel layer thickness on the gate voltage and is not valid at very high frequencies such as the

Summary

Introduction

Thin-film transistor (TFT) technology has found numerous applications including large area and flexible displays [1,2], sensitive skin [3], biomedical and chemical sensors [4], and radio frequency identification (RFID) sensors [5]. Technologies and allowed for emerging higher frequency applications (even into the THz range) as shown in this paper Supporting these applications requires the development of advanced compact models for TFTs to complement the numerical simulations [15,16,17]. The conventional RPI TFT model does not account for the dependence of the channel layer thickness on the gate voltage and is not valid at very high frequencies such as the THz range. Nanomaterials 2022, 12, 765 used for the THz SPICE Si CMOS model implementation [20,21] These novel features enable an excellent fitting with the measured DC characteristics for TFTs and significantly extend the application frequency range of the TFT model.

Model Details

Cutoff Frequency

Application to THz Detection

Conclusions