The influence of growth conditions on carrier lifetime in 4H–SiC epilayers.

Abstract: 4H–SiC homoepitaxial layers have been grown in a horizontal hot-wall CVD (chemical vapor deposition) reactor and the measured carrier lifetimes have been correlated to the CVD growth conditions. Two different generations of reactors were compared, resulting in measured carrier lifetimes in two different orders of magnitude, from a few hundreds of ns to a few µs. The variations in measured carrier lifetime were correlated to deep level concentrations of the Z 1/2 center and the D 1 center, seen by photoluminescence. Decreasing the growth temperature clearly prolonged the carrier lifetime and showed lower Z 1/2 concentrations, whereas lowering the growth rate only showed a small improvement of the carrier lifetime and no obvious tendency in Z 1/2 defect concentrations, indicating that Z 1/2 is not the only defect limiting the carrier lifetime. Increasing the C/Si ratio resulted in decreasing Z 1/2 concentrations, indicating the carbon vacancy nature of the defect. However, carrier lifetime measurements showed maximum values for a C/Si ratio of 1 but otherwise an increasing tendency for increasing C/Si ratios. The reactor giving higher carrier lifetimes, correspondingly also showed lower Z 1/2 concentrations indicating the lifetime limiting property of Z 1/2. Furthermore, the D 1 defect intensity increased with growth temperature and decreased with increasing C/Si ratio, similar to the Z 1/2 concentration. [Copyright &y& Elsevier]