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

Deep levels in n-type 4H-SiC epilayers have been investigated by deep level transient spectroscopy (DLTS). The Z(1/2) 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 Z(1/2) and EH6/7 concentrations are significantly increased. The Z(1/2) and EH6/7 centers are stable up to 1500-1600 degrees C and their concentrations are decreased by annealing at 1600-1700 degrees C. In the irradiated samples, the trap concentrations of the Z(1/2) and EH6/7 centers are increased with the 0.7 power of the electron fluence. The concentrations of the Z(1/2) 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 Z(1/2) and EH6/7 centers microscopically contain the same defect such as a carbon vacancy. (c) 2006 American Institute of Physics.