Deep-subthreshold Schottky barrier IGZO TFT for ultra low-power applications

Abstract

This study reports the deep subthreshold characteristics (≤1 V) of low thermal budget Indium Gallium Zinc Oxide (IGZO) thin film transistors (TFTs) with Schottky barrier source/drain contacts. The Schottky barrier was analyzed and a consistent ideality factor was observed across the devices. A deep subthreshold region was extracted from the nominal characteristics and barrier influence was observed in the low voltage region. This operation led to high output impedance (~10¹²Ω) and excellent trans-conductance leading to a high voltage gain (>100) due to hard saturation of the output characteristics. Positive bias stress and stability tests were conducted within this region that showed minimal drift in the transfer characteristics. Such characteristics make these devices an excellent choice for low-power deep subthreshold and weak signal applications.