Long range lateral migration of intrinsic point defects in n-type 4H-SiC

Abstract

The lateral distributions of intrinsic point defects in n-type (0001) 4H-SiC have been investigated following room temperature irradiation with a focused beam of 10 keV protons. Laterally resolved deep level transient spectroscopy measurements reveal that the well-known and prominent Z1/2 and S1/2 centers display lateral diffusion lenghts on the order of 1 mm with negligible (if any) motion parallel to the direction of the c-axis. The migration occurs only in the presence of excess charge carriers generated during the proton irradiation, and no further motion takes place even under subsequent optical excitation of high intensity. Assuming one-dimensional geometry, an effective defect diffusivity in excess of 10−6 cm2/s is deduced by numerical modelling of the experimental data, corresponding to an energy barrier for migration of ∼0.2 eV. Possible mechanisms for the rapid migration, invoking charge carrier recombination as a necessary condition, are discussed, and especially, an association with the glide of partial dislocations along the (0001) basal plane is scrutinized in some detail.