  Thick, high-purity semi-insulating (SI)homoepitaxial layers on Si-face 4H-SiC
weregrownsystematically, with resistivity \geq 109{\Omega}-cmby maintaining
high C/Si ratios 1.3-15 during growth.Comparison of secondary ion mass spectra
betweenlow-dopedepilayers grown at C/Si ratio<1.3andSI-epilayers grown at C/Si
ratio>1.3 showed little difference in residual impurity concentrations. A
reconciliation of impurity concentration with measured resistivity indicated a
compensating trap concentration of ~1015cm-3present only in the SI-epilayers.
High- resolution photo induced transient spectroscopy (HRPITS) identified
themas Si-vacancy related deep centers, with no detectable EH6/7 and
Z1/2levels. Recombination lifetimes ~5ns suggest application in fast-switching
power devices.
