Near-Interface Trap Model for the Low Temperature Conductance Signal in SiC MOS Capacitors With Nitrided Gate Oxides

Abstract

The low channel-carrier mobility in commercial SiC MOSFETs has been attributed to fast electron traps labeled “NI.” These traps exhibit anomalous behavior compared to other interface trap signals. Furthermore, the electrical parameters extracted from a conventional interface trap analysis of the NI signal are not physically reasonable. To explore the origin of these traps, we fabricated SiC MOS capacitors and measured the conductance across a range of temperatures (between 50 and 300 K). By analyzing the surface electron density at the signal peaks, it is evident that these traps are in fact near-interface traps (NITs)—they are located within the oxide and exchange electrons via a tunneling mechanism. We also developed a model for the conductance generated by NITs and demonstrated a good fit to the experimental data. The knowledge that the NI signal is due to NITs will help in directing future efforts to improve SiC MOSFET performance.