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 8.2MeV electron-irradiated 4H-SiC Schottky diodes were investigated. Deep-level transient spectroscopy and minority-carrier diffusion length (Ld) measurements were carried out on not-irradiated samples and on irradiated samples before and after thermal treatments up to T=450°C. We found that several deep levels in the upper half band gap (S1 with enthalpy ET=0.27eV, S2 with ET=0.35eV, S4 with ET=0.71eV, and S5 with ET=0.96eV) anneal out or modify at temperature values lower or equal to T=450°C, whereby their progressive annealing out is accompanied by a net increase of Ld, 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.