Evaluation of interface trap characterization methods in 4H-SiC metal oxide semiconductor structures over a wide temperature range

Abstract

In this paper, four widely used interface trap characterization methods based on quasistatic and high-frequency capacitance–voltage (CV) and conductance–frequency (Gω) measurements are evaluated at thermally oxidized 4H-SiC metal oxide semiconductor structures. To cover a wide range of defect levels in a wide bandgap semiconductor, the CV and Gω measurements are conducted at temperatures ranging from 150 to 600 K. Interface trap densities Dit are extracted using the high-frequency Terman method, the low frequency capacitance method, the high-low frequency method, and the conductance method. A very good agreement between the different methods is observed in restricted energy ranges. The use of the conductance method allowed for the determination of defect states in an energy range of almost 800 meV. A strong hysteresis of bidirectional CV curves is observed at different temperatures and is used to estimate border trap densities. The presence of mobile charges in the oxide is found to be a limiting factor for high temperature CV measurements. Low temperature Gω measurements revealed a second conductance peak which is identified as the 100 meV nitrogen donor level.