Evaluation of thermally activated defects behaviors in nitrogen-doped Czochralski silicon single crystals using deep level transient spectroscopy

Abstract

Thermally activated defect behaviors in nitrogen (N)-doped Czochralski silicon (Cz-Si) single crystals were investigated using deep level transient spectroscopy and quasi-steady-state photoconductance to confirm the crystals’ applicability in insulated gate bipolar transistors (IGBTs). The thermally activated defects, which were probably N-vacancy complexes and degraded the minority carrier lifetime, were detected with extremely low densities in N-doped Cz-Si compared with N-rich floating zone Si single crystals after heat treatments at 500 °C, resulting in a high remaining value of minority carrier lifetime. The difference was assumed to come from whether vacancies were released in the Si matrix during heat treatment. For the Cz-Si, vacancies were assumed to be strongly bound with oxygen atoms with concentrations of 1017 atoms cm−3. Therefore, vacancies were not released during heat treatment, resulting in low remaining N-vacancy complex densities. N-doped Cz-Si are potential materials for IGBTs because of their low densities from thermally activated defects.