Diffusion length and junction spectroscopy analysis of low-temperature annealing of electron irradiation-induced deep levels in 4H-SiC

The effects of low-temperature annealing in 8.2 MeV electron-irradiated 4H-SiC Schottky diodes were investigated. Deep-level transient spectroscopy and minority-carrier diffusion length (L-d) measurements were carried out on not-irradiated samples and on irradiated samples before and after thermal treatments up to T=450 degrees C. We found that several deep levels in the upper half band gap (S1 with enthalpy E-T=0.27 eV, S2 with E-T=0.35 eV, S4 with E-T=0.71 eV, and S5 with E-T=0.96 eV) anneal out or modify at temperature values lower or equal to T=450 degrees C, whereby their progressive annealing out is accompanied by a net increase of L-d, up to 50% of the value in the as-irradiated sample. We drew some conclusions regarding the microscopic nature of the defects related to the deep levels, according to their annealing behavior.(c) 2006 American Institute of Physics.