Comparison of Conduction Mechanisms in Heavily Al-Doped 4H-SiC and Heavily Al- and N-Codoped 4H-SiC

The conduction mechanism in heavily Al-doped or heavily Al-and N-codoped p-type 4H-SiC epilayers was investigated. In both the singly-doped and codoped samples with an Al concentration (CAl) between 4x1019 and 2x1020 cm-3, band and nearest-neighbor hopping (NNH) conductions appeared in high and low temperature ranges, respectively. The codoping of N donors makes the NNH conduction dominant at temperatures higher than in the singly-doped samples. In both the singly-doped and codoped samples with CAl between 1x1019 and 4x1019 cm-3, an unexpected conduction appeared between the regions of the band and NNH conductions.