Zinc tin oxide metal semiconductor field effect transistors and their improvement under negative bias (illumination) temperature stress

Metal-semiconductor-field-effect-transistors (MESFETs) with silver oxide Schottky gates on zinc tin oxide (ZTO) channels showed fundamental differences in stability compared to conventional amorphous-oxide semiconductor thin-film-transistors (AOS-TFTs). The most severe negative-bias-temperature and negative-bias-illumination-temperature stress conditions, which usually degrade the performance of AOS-TFTs, significantly improved the switching characteristic of these ZTO MESFETs, producing devices with on:off current ratios, mobilities, and subthreshold swings of 8 × 10⁶, 12 cm² V⁻¹ s⁻¹, and 180 mV/dec, respectively. Further analysis confirmed that both negative bias and temperature (65 °C) were simultaneously required to produce this permanent effect that was linked to the electromigration of ionized donors from the MESFET depletion-region.