Materials Science Forum, Vol.433-4, 463-466, 2002
Deep levels in as-grown 4H-SiC epitaxial layers and their correlation with CVD parameters
Nitrogen doped 4H-SiC epitaxial layers grown by hot-wall chemical vapor deposition were investigated by deep level transient spectroscopy in the as-grown state. Besides the Z(1,2) defect level at E-C - 0.66 eV, that seems to be omnipresent, four other electron traps labeled IL1 to IL4 With ionization energies between 0.87 and 1.31 eV could be detected. The dependence of the deep level concentrations on the incorporated N concentration ranging from few 10(14) to Some 10(15) cm(-3) and the C/Si ratio (1.2divided by3) was examined. The concentration of both Z(1,2) and IL1 increases with increasing N doping. For medium C/Si ratios this dependence is linear for Z(1,2) and quadratic for IL1. High C/Si ratios enhance the formation of Z(1,2) while they suppress that of IL1. These results suggest a complex of interstitial C and N on carbon site (C-i-N-C) for Z(1,2) and a nitrogen pair (N-C-N-i) for IL1. However, other possibilities like Si vacancy related defects cannot be ruled out at present.