Electrically active defects in n-type 4H–silicon carbide grown in a vertical hot-wall reactor

We have studied intrinsic and impurity related defects in silicon carbide (SiC) epilayers grown with fast epitaxy using chemical vapor deposition in a vertical hot-wall reactor. Using capacitance transient techniques, we have detected low concentrations of electron traps (denoted as ${\mathrm{Z}}_{\text{1/2}},$ EH6/7 and titanium) and hole traps (denoted as HS1 and shallow boron) in the n-type 4H–SiC epilayers. The concentration of intrinsic defects $({\mathrm{Z}}_{\text{1/2}},$ EH6/7, and HS1 centers) increases with increasing growth temperature. The incorporation of shallow boron (B) decreases at higher growth temperatures, whereas the titanium (Ti) concentration is not sensitive to the growth temperature. The concentration of shallow B and Ti increases with increasing C/Si ratio. The concentration of the EH6/7 and the HS1 centers however, decreases with increasing C/Si ratio. We have also tested graphite susceptors with TaC or SiC coating and observed that the purity of the susceptor material plays a critical role in reducing the background impurity incorporation. The correlation with the carrier lifetime of these epilayers indicates that the EH6/7 and the ${\mathrm{Z}}_{\text{1/2}}$ centers may be the lifetime limiting defects in the investigated epilayers.