Investigation of Deep Levels and Residual Impurities in Sublimation-Grown SiC Substrates

Deep levels and residual impurities in sublimation-grown n-type SiC substrates are investigated. Three electron trap centers at 0.26, 0.35 and 0.72 eV below the conduction band (CB) are observed in 4H-SiC for the first time by deep-level transient spectroscopy (DLTS). One electron trap center at 0.68 eV below the CB is also observed in n-type 6H-SiC. The trap concentration and capture cross section are estimated. The concentration of residual impurities V, Cr, Fe and Ti are found to be high. The origin of observed trap centers is discussed with respect to the residual impurities and available information.