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 ${\sim}10^{9}$ $\Omega$ 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 ${\sim}10^{15}$ 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 ${\sim}5$ ns suggest application in fast-switching power devices.