Carrier lifetime killer in 4H-SiC: carrier capture path via carbon vacancies

Abstract

Carbon vacancies are thermally stable and are the most commonly observed native point defects in 4H-SiC, the key wide-bandgap semiconductor in power electronics. They are also identified as the physical original of Z_1/2 and EH_6/7 deep levels which are important carrier lifetime killers. However, the microscopic recombination process and detailed carrier capture path around carbon vacancies remain unclear. Leveraging upon first principles calculations, this work comprehensively investigates the carrier capture path and corresponding capture coefficients of carbon vacancies in 4H-SiC which are consistent with experimental observations. The findings also reveal the metastable spin-triplet carbon vacancies as key transition states in completing the non-radiative carrier capture path, especially at the donor levels. These metastable carbon vacancies can be formed either during the materials growth or through spin-selective carrier capture. This finding helps address the discrepancy in the association of EH_6/7 and Z_1/2 levels in experimental observation and provides deeper insights into the nature of carrier recombination in 4H-SiC.