Impact of heavy ions on a-Si:H/PolySi bilayer thin film transistors with Schottky barrier source and drain based on Nickel Silicide

This study investigates the influence of heavy ion irradiation on thin film transistors (TFTs) based on an a-Si:H/PolySi active layer and Schottky barrier-based source and drain. Through the use of Technology Computer-Aided Design (TCAD) simulations, we analyze the impact on device performance. We examine the ambipolar device characteristics by varying the thickness of the active layer (Poly-Si) and studying the corresponding physics. Our results reveal that reducing the active layer thickness from 140 to 80 nm decreases the magnitude of the threshold voltage (|VT|) for both nMOS and pMOS operating voltages. Additionally, the subthreshold slope is reduced for both nMOS and pMOS as the active layer thickness is decreased from 140 to 80 nm.

Further, we investigated the transient response of the drain current to heavy ion irradiation in the sensitive regions across the Schottky barrier-based source and drain. We specifically analyze the phenomenon of bipolar amplification for various Linear Energy Transfer (LET) values, ranging from 0.1 MeV cm²/mg to 100 MeV cm²/mg. Our findings indicate that increasing the LET values from 0.1 MeV cm²/mg to 100 MeV cm²/mg results in amplified bipolar behavior and a drain current overshoot of over 10 % for both pMOS and nMOS operating voltages. To summarize, this work highlights the effects of heavy ion irradiation on TFTs with an a-Si:H/PolySi active layer and Schottky barrier-based source and drain. The study explores the influence of active layer thickness on device characteristics and demonstrates the transient response of drain current under different LET values. These findings contribute to a better understanding of the behavior and performance of TFTs subjected to heavy ion irradiation.