Depth profiles of deep levels generated in the tail region of Al ion implantation into n-type 4H-SiC

Depth profiles of deep levels in the tail region of Al ion implantation in n-type 4H-SiC were investigated by deep level transient spectroscopy measurements. Deep levels energetically located at E c - 0.55 eV, E c - 0.64 eV, and E c - 1.50 eV (E c: conduction band bottom) are generated in the tail region by the implantation and subsequent activation annealing at 1750 degrees C for 20 min. The densities of these defects were approximately 20-40 times lower than the implanted Al atom density, and the densities of these defects and Al atoms exhibited an exponential decay along the depth direction with a decay length of 140-190 nm. Another deep level located at E c - 1.30 eV was detected in the tail region and the density of this trap decreased more rapidly with a decay length of 62 nm. The origins of the observed deep levels are discussed based on several experimental results.