Effect of Voltage Probes on the Characterisation of Switching Processes in Wide-bandgap Semiconductor Devices

The high switching speed of wide-bandgap (WBG) semiconductor devices puts higher requirements on the measurement accuracy and intrusion effects of voltage probes. This paper analyses the influence of input capacitance and parasitic inductance of voltage probes on the characterization of switching processes from the point of view of measurement accuracy and the intrusion effect of probes. It analyses the reason why the latest opto-isolated probes measure the gate-source voltage affecting the switching process. The GaN HEMT-based double-pulse experiment verifies the correctness of the theoretical analysis. The performance of different voltage probes and different methods for measuring gate-source voltage and drain-source voltage of WBG devices is systematically compared. The results indicate that conventional high-voltage differential probes fail to meet the testing requirements due to insufficient bandwidth and excessive parasitic inductance. Opto-isolated probes demonstrate superior performance with high bandwidth and low input capacitance. However, forward-direction measurements are critical to avoid the reverse connection's grounding capacitance impact on switching. This study provides guidance on probe selection and measurement methodologies for accurate characterization of dynamic characteristics in WBG semiconductor devices.