Current-voltage characteristics and DLTS spectra of high voltage SiC Schottky diodes irradiated with electrons at high temperatures

Abstract

The effect of the electron irradiation at high temperatures Ti (300 and 500 °C) and of the subsequent annealing on the current–voltage characteristics and DLTS spectra of high-voltage integrated 4H-SiC Schottky diodes is compared for the first time. The optimal annealing modes of the structures irradiated with 0.9 MeV electrons are determined. It is shown that the irradiation with a relatively low fluence Φ = 1016 cm−2 at 300 °C leads to an increase in the base resistance Rb by approximately an order of magnitude, and the initial value of Rb can be completely restored by a single annealing in a nitrogen atmosphere at a temperature of 250 °C for 60 min. At the same time, however, annealing affects only slightly the DLTS spectra measured after the irradiation. With increasingΦ, the longer annealing is required to fully restore the Rb. However, with the fluence increasing to Φ ≥ 5 × 1016 cm−2, the effect of a “reverse annealing” was observed in SiC for the first time: the resistance of the base grows as a result of the annealing. Irradiation at temperature of 500 °C leads at Φ ≥ 5 × 1016 cm−2 to an even more pronounced effect of reverse annealing. It is demonstrated that the presence of DLTS-detected acceptor centers arising as a result of the “hot” irradiation in the upper half of the band gap can explain neither the change in the current–voltage characteristics nor the results of annealing.