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

摘要

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 (300 K) using an americium-241 (~(241)Am) radionuclide source. DLTS revealed the presence of four deep levels in the as-grown samples, E_(0.09). E_(0.11). £0.16 and E_(0.65). After irradiation with a fluence of 4.1 × 10~(10) alpha-particles-cm~(-2), DLTS measurements indicated the presence of two new deep levels, E_(0.39) and E_(0.62) with energy levels, E_C - 0.39 eV and E_C - 0.62 eV, with an apparent capture cross sections of 2 × 10~(-16) and 2 × 10~(-14) cm~2, respectively. Furthermore, irradiation with fluence of 8.9 × 10~(10) alpha-partides-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 ℃ for 20 min. Defects, E_(0.39) and E_(0.42) 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 E_C - (0.55-0.70) eV (known as Z_1/Z_2) were attributed to an isolated carbon vacancy (V_C).