Investigation of deep levels in n-type 4H-SiC epilayers irradiated with low-energy electrons

Abstract

Deep levels in n-type 4H-SiC epilayers have been investigated by deep level transient spectroscopy (DLTS). The Z1∕2 and EH6∕7 centers are dominant in as-grown samples. After electron irradiation at 116 keV, by which only carbon atoms may be displaced, the Z1∕2 and EH6∕7 concentrations are significantly increased. The Z1∕2 and EH6∕7 centers are stable up to 1500–1600 °C and their concentrations are decreased by annealing at 1600–1700 °C. In the irradiated samples, the trap concentrations of the Z1∕2 and EH6∕7 centers are increased with the 0.7 power of the electron fluence. The concentrations of the Z1∕2 and EH6∕7 centers are very close to each other in all kinds of samples, as-grown, as-irradiated, and annealed ones, even though the condition of growth, irradiation (energy and fluence), and annealing has been changed. This result suggests that both Z1∕2 and EH6∕7 centers microscopically contain the same defect such as a carbon vacancy.