Amorphous Ga2O3 Semiconductor: A New Solution for Robust X-Ray Dosimeters

Abstract

As most commonly used miniature solid-state dosimeter, metal-oxide-semiconductor field effect transistors (MOSFETs) have been facing unavoidable gate leakage and robustness problems due to the double-sided role of traps in oxide insulators. Herein, a new solution for X-ray dosimeter has been proposed which leverages the conductivity change of amorphous Ga2O3 (a-Ga2O3) channel instead of charge trapping in oxide insulators. Increasingly negatively-shifted threshold voltage (Vth) of a-Ga2O3 thin-film transistor is recorded together with almost unchanged subthreshold swing (SS) and field-effect mobility (µFE) after X-ray irradiations. X-ray-induced-variation of oxygen vacancy (VO) related defects in a-Ga2O3 is revealed after a combined investigation of X-ray photoelectron spectroscopy (XPS) and neutron reflectivity (NR) measurements, contributing to the indicative Vth shift related with X-ray dosage. A functional recovery is realized through an annealing process in air condition, showing the high reliability of a-Ga2O3 semiconductor. Moreover, the unique merit of no need for power supply during X-ray irradiations, beneficial from the slow neutralization rate of ionized VO related defects, imparts an offline working capability to the dosimeter. This work provides a potential strategy to monitor X-ray dosage via utilizing the X-ray-induced change of amorphous oxide semiconductor conductivity, hence addressing the reliability and repeatability issues in present MOSFET devices.