Abstract:The threshold voltage, internal gate resistance, and the gate capacitance are the key electrical parameters of silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs). However, extractions of them are complicated and prone to inaccuracy due to the limited factors of the parasitic resistance, gate-dielectric interfacial states in the devices. Therefore, through device modeling and experimental testing, the nonlinear characteristics of gate capacitance of MOSFETs were revealed, and a capacitance-resistance series circuit test method was constructed. Then, the internal gate resistance and threshold voltage characteristics of SiC MOSFETs were studied. The relationship between the gate impedance and gate-source voltage, and that between the gate capacitance and gate-source voltage, are achieved in this paper, revealing that the error between the gate internal resistance obtained at the gate voltage of -10 V, and the target value is less than 0.5 Ω. Meanwhile, the approximate value of the threshold voltage is the gate voltage at which the series capacitor significantly varies with respect to the gate-source voltage. The results are compared with these attained by the constant current method, and verified in SiC planar-gate and trench-gate MOSFETs, respectively. Therefore, this capacitance-resistance method provides a relatively convenient method for evaluating and predicting the characteristics of the threshold voltage drift and gate switching oscillations in SiC MOSFET.
