The influence of hydrogen annealing on minority carrier lifetimes in 4H-SiC

In this study, 4H-SiC with different thickness and doping types were annealed in hydrogen at low pressure, the minority carrier lifetimes of which were investigated by microwave photoconductive decay (
$\mu$
-PCD). It can be observed that the minority carrier lifetime of 4H-SiC will increase and decrease repeatedly after each hydrogen annealing. The phenomenon is due to the surface states and hydrogen passivation instability. After ten times of hydrogen annealing, the minority carrier lifetimes of all the samples showed an increasing trend. This may be due to the dual mechanism of hydrogen passivation and selective etching. The surface roughness of the sample before and after hydrogen annealing were also measured and discussed by atomic force microscopy(AFM).