A discussion on the DC and switching performance of a gallium nitride CAVET for 1.2kV application

A cascoded GaN Current Aperture Vertical Electron Transistor (CAVET), which incorporates a normally off low-voltage Si MOSFET at the input and a normally on high-voltage GaN CAVET at the output in a cascode form, has been simulated and analyzed using a device/circuit hybrid simulator implemented in Silvaco ATLAS. The hybrid simulator was achieved by integrating the Silvaco ATLAS based 2D drift-diffusion simulator with the SPICE based circuit simulator. This model provides a reliable method of evaluating GaN-based power transistor. A baseline of the hybrid simulator was first established using commercial cascoded GaN HEMT where a good agreement of simulated data and device specs as published on the datasheet was obtained. The hybrid simulator was then applied to compare SiC and GaN power devices using commercial MOSFET and JFET for SiC and a CAVET in GaN. A cascoded GaN CAVET has 2x faster switching time, 6x lower switching loss than standard commercial SiC MOSFET and JFET, suggesting its potential advantage over SiC devices for power converters. Another advantage of cascoded GaN CAVET is that it enables switches operating at frequencies of several hundreds of kilohertz with low power loss, which enable smaller converter size and high system efficiency.