Dynamic space-charge-controlled field emission model of current conduction in metal-insulator-semiconductor capacitors

Abstract

A dynamic space-charge-controlled field emission (SCC-FE) model that considers temporal insulator charge variations caused by voltage stress is developed for analyzing the current conduction in insulators in the entire voltage range of measurement, yielding good agreement between experiments and simulations. The usage of prestressed samples in this analysis is essential for accurately estimating the electron affinities of insulators, yielding 1.65 and 1.93 eV as the estimates for Al2O3 films formed on GaN by atomic-layer deposition (ALD) at 200 and 450 °C, respectively, and 1.65 and 1.83 eV for those on SiO2/Si, respectively. Through the bias instability analysis using the method developed here, the voltage-stress tolerance of both Si and GaN metal-insulator-semiconductor (MIS) capacitors with ALD Al2O3 films was found to be enhanced by the high-temperature (450 °C) ALD. The analysis also revealed the fact that the voltage-stress-induced flatband voltage shift of GaN capacitors with the high-temperature Al2O3 films is mainly caused by the Al2O3 charges near the substrate, hence providing a clue to even better bias stability of the GaN capacitors. With possible applications to other wide-bandgap semiconductor (WBGS) capacitors, the dynamic SCC-FE analysis developed here will play an essential role in analyzing not only gate insulator characteristics but also many reliability issues of various WBGS MIS field-effect transistors.