Dynamic characterization of SiC and GaN devices with BTI stresses

The use of temperature sensitive electrical parameters for condition monitoring of power devices is widely acknowledged for conventional Si power devices. However, its use for wide bandgap devices is still the subject of research thereby making the electrothermal characterization of these devices a requirement, especially for GaN power devices. This paper investigates and compares the dynamic characteristics of SiC and GaN power devices and how these characteristics are affected by bias temperature instability from gate voltage stress. Results show that turn-ON dI_D/dt increases with temperature in SiC whereas it decreases with temperature in GaN. Turn-OFF dV_DS/dt is marginally temperature dependent in both technologies. These electrical parameters can be subject to drift from gate oxide degradation due to charge trapping and threshold voltage drift. Initial V_GS stress tests (at the rated voltages) on SiC and GaN devices show no apparent shift in V_TH, however more sophisticated test methods using the body diode voltage as an indicator for V_TH showed rapid V_TH shift and recovery (within a few seconds) in SiC MOSFETs.