Investigation of deep levels in nitrogen doped 4H–SiC epitaxial layers grown on 4° and 8° off-axis substrates

Intentionally doped n-type 4H–SiC films were grown on 4° and 8° off-axis substrates to investigate the influence of electron concentration on the incorporation of electron traps Z_1/2 and EH_6/7. No discernible change was seen in the Z_1/2 and EH_6/7 trap concentrations for films grown on both orientations with electron concentrations in the range of 1×10¹⁴ to 1×10¹⁶ cm^-3, suggesting that the Z_1/2 and EH_6/7 traps are not associated with isolated carbon vacancies. The defect concentrations did not correlate with the measured carrier lifetimes, which is consistent with a carrier lifetime controlled by other recombination centers. Observed decreases in lifetime were related to increases in doping levels, with similar trends seen for both orientations. Carrier lifetimes in 8° material were slightly longer than in 4° films for similar doping concentrations, most likely being associated with surface recombination and/or extended defects.