Electrical characterization of deep levels created by bombarding nitrogen-doped 4H-SiC with alpha-particle irradiation

Abstract

Deep-level transient spectroscopy (DLTS) and Laplace-DLTS were used to investigate the effect of alpha-particle irradiation on the electrical properties of nitrogen-doped 4H-SiC. The samples were bombarded with alpha-particles at room temperature (300K) using an americium-241 (241Am) radionuclide source. DLTS revealed the presence of four deep levels in the as-grown samples, E0.09, E0.11, E0.16 and E0.65. After irradiation with a fluence of 4.1×1010 alpha-particles-cm−2, DLTS measurements indicated the presence of two new deep levels, E0.39 and E0.62 with energy levels, EC – 0.39eV and EC – 0.62eV, with an apparent capture cross sections of 2×10−16 and 2×10−14cm2, respectively. Furthermore, irradiation with fluence of 8.9×1010 alpha-particles-cm−2 resulted in the disappearance of shallow defects due to a lowering of the Fermi level. These defects re-appeared after annealing at 300°C for 20min. Defects, E0.39 and E0.42 with close emission rates were attributed to silicon or carbon vacancy and could only be separated by using high resolution Laplace-DLTS. The DLTS peaks at EC – (0.55–0.70)eV (known as Z1/Z2) were attributed to an isolated carbon vacancy (VC).