High Purity Semi-Insulating 4H-SiC Epitaxial Layers by Defect-Competition Epitaxy: Controlling Si Vacancies

Thick, high-purity semi-insulating (SI) homoepitaxial layers on 4H-SiC were demonstrated using a novel compensation scheme controlled by defect-competition epitaxy at C/Si ratios of 1.3–1.5. These showed resistivity of ~109 Ω cm. Comparison of secondary ion mass spectra between low-doped 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 ~1015 cm-3 present only in SI epilayers. High-resolution photoinduced transient spectroscopy (HRPITS) identified them as Si vacancy related centers, with no detectable EH6/7 and Z1/2 levels. Recombination lifetimes of ~5 ns suggest application in fast-switching power devices.