On the application of novel high temperature oxidation processes to enhance the performance of high voltage silicon carbide PiN diodes

Abstract

In this paper, the application of a combined high temperature (1550°C) thermal oxidation / annealing process has been applied to 4H-SiC PiN diodes with 110 μm thick n-type drift regions, for the purpose of increasing the carrier lifetime in the semiconductor. PiN diodes were fabricated on lifetime-enhanced 4H-SiC material, then were electrically characterised and compared against fabricated control sample PiN diodes. Forward current-voltage (I-V) measurements showed that the lifetime-enhanced devices typically had around 15% lower forward voltage drop and 40% lower differential on-resistance (at 100 A/cm2 and 25°C) when compared against control sample PiN diodes. Reverse I-V measurements indicated that the reverse leakage current was strongly dependent on the active area, and hence perimeter-to-area ratio, of the fabricated devices, though large-area PiN diodes were measured to have a reverse leakage current density of around 1 nA/cm2 (at 100 V reverse bias). Analysis of reverse recovery characteristics illustrated the excellent transient characteristics of both types of fabricated device, though, as expected from the increased carrier lifetime, the lifetime-enhanced PiN diodes had around 22% higher reverse recovery charge. The minority carrier lifetime was also extracted from reverse recovery characteristics; PiN diodes fabricated on the lifetime-enhanced 4H-SiC material were found to have a carrier lifetime over 35% higher than the control sample devices. Analysis of the overall power losses of both types of device found that the lifetime-enhanced PiN diodes typically dissipated around 40% less energy over the complete switching cycle than the control sample PiN diodes at 25°C.