Oxide and Interface Defect Analysis of lateral 4H-SiC MOSFETs through CV Characterization and TCAD Simulations

We investigated oxide and interface defects of lateral 4H-SiC MOSFETs through capacitance-voltage (C-V) and conductance-voltage (G-V) characterization at various frequencies and temperatures. By employing consecutive up and down sweeps of the gate voltage at three different temperatures, we experimentally characterized the hysteresis width as the difference between up and down sweeps in the depletion to accumulation (d-a) and depletion to inversion (d-i) regions. We observed an increase in the hysteresis width with decreasing temperature. Although the hysteresis width is not affected by the small-signal frequency, at the same time, increasing the frequency leads to a strong stretch-out effect, especially in the d-i region.Our measurement results indicate that the hysteresis deformation of the C-V curves is dominated by three different trap types. First, interface acceptor-like defects located close to the conduction band can follow the small-signal frequency. Slower acceptor-like border traps with trap levels both close to the conduction band and in the middle of the band gap are however responsible for the increase of trapped negative charge with increasing gate voltage. Finally, we assume the presence of a fixed positive charge.