Current conduction mechanisms in post-nitridation rapid-thermal-annealed gate oxides on 4H silicon carbide

Abstract

In this letter we report current-conduction mechanisms in nitrided gate oxides on n-type 4H SiC subjected to various rapid-thermal-annealing temperatures. The experimental results show that by increasing SiC-SiO2 interface trap density, current conduction in the oxide is increased. Fowler-Nordheim (FN) tunneling which is assisted by SiC-SiO2 interface trap is responsible to the current conduction. In contrast, the current conduction through the oxide is significantly reduced when the oxide is having a multiple discrete energy level of electron trap center. This center enables trapping of electrons that are injected from SiC substrate via FN tunneling, causing a reduction in leakage current and an improvement in oxide breakdown strength. Based on the results, a model has been hypothesized and reasons for these observations have been presented.