A Simple, High-Speed Measurement Technique for Dynamic on-resistance of GaN Devices for Hard-Switched Pulsed Power Applications

GaN devices offer ultra-fast switching, superior electrical performance, and radiation hardness – making them a favorable choice for pulsed power applications. One potential drawback is the high on-resistance of GaN devices under switching conditions (dynamic $R_{on}$), which is not often publicly characterized by manufacturers. Previous research attempts have observed high dynamic $R_{on}$ in continuous switching conditions, sometimes with accurate measurements only after long delays from the switching instant-making their data of limited value for low-duty, high-speed pulsed power systems. This work proposes a fast measurement approach with minimal additional circuitry, designed specifically for pulsed conditions. Using this approach, dynamic $R_{on}$ measurements are reported for devices across several manufacturers, sizes (static $R_{on}$), blocking voltages and drain currents. For the 650 V-rated discrete (non-composite) devices, the measured dynamic $R_{on}$ values are found to be higher than their respective static values by a factor of 1.5x-3x. Whereas, the 650 V-rated cascode (composite) devices and 100 V-rated discrete devices are found to experience a negligible dynamic $R_{on}$ effect.