TCAD-based Analysis of Dynamic Transients of 4H-SiC Vertical NPN BJT

This paper presents experimental evaluation of dynamic performance of high voltage 4H-SiC NPN BJT, analysed through modelling in Silvaco TCAD. The measurements are performed with a DC-link voltage of 800 V at peak collector current of 14 A with different base currents and load inductors. The TCAD model is validated by comparing its output static characteristics with datasheet. The absence of delay in 4H-SiC BJTs is due to the lower minority carrier lifetime and thinner base region, enabling higher DC current gain and significantly faster transients. However, a current drop phenomenon is visible in steady-state operation of 4H-SiC BJT, seen in both measurements and TCAD modelling. This is due to the peak collector current for a fixed base current impacted by its thinner base and the Early effect.