Surface defects in 4H-SiC: properties, characterizations and passivation schemes

Silicon carbide (SiC) is a typical wide band-gap semiconductor material that exhibits excellent physical properties such as high electron saturated drift velocity, high breakdown field, etc. The SiC material contains many polytypes, among which 4H-SiC is almost the most popular polytype as it possesses a suitable band-gap and high electron saturated drift velocity. In order to produce 4H-SiC power devices with a high barrier voltage of over several thousand volts, the minority carrier lifetime of 4H-SiC single crystals must be carefully managed. In general, both bulk defects and surface defects in 4H-SiC can reduce the minority carrier lifetime. Nevertheless, as surface defects have received less attention in publications, this study reviews surface defects in 4H-SiC. These defects can be classified into a number of categories, such as triangle defect, pit, carrot, etc. This paper discusses each one individually followed by the introduction of industrially feasible methods to characterize them. Following this, the impact of surface defects on the minority carrier lifetime is analyzed and discussed. Finally, a particular emphasis is put on discussing various passivation schemes and their effects on the minority carrier lifetime of 4H-SiC single crystals. Overall, this review paper aims to help young researchers comprehend surface defects in 4H-SiC single crystal material.