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

摘要

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 ~10~9 Ω cm. Comparison of secondary ion mass spectra between low-doped epilayers grown at C/Si ratio <1.3 and SI 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 ~10~(15) cm~(-3) present only in SI epilayers. High-resolution photoinduced transient spectroscopy (HRPITS) identified them as Si vacancy related centers, with no detectable EH_(6/7) and Z_(1/2) levels. Recombination lifetimes of ~5ns suggest application in fast-switching power devices.