DLTS measurement of energetic levels, generated in silicon detectors

DLTS (deep level transient spectroscopy) measurements were performed on irradiated Si detectors to record data on the energetic levels traps generated by neutrons. For moderate fluences (φ) of neutrons (φ < 1012 n cm−2) electron and hole trap levels have been detected. Four electron trap levels were found for both FZ (float zone) and MCZ (magnetic Czochralsky) types of Si detectors but only two hole trap levels in FZ and one in MCZ detectors. This indicates that the type of silicon has an influence on the traps generated by irradiation. From the values obtained for the relative concentration of E1 centers in MCZ and FZ detectors, it results that the E1 centers are oxygen and not vacancy limited. Since the concentration of the E2, E3, and E4 levels are larger in FZ than in MCZ detectors, it may be assumed that the “gettering effect” can control the formation of deeper traps. Filling pulses were applied for various voltages and at the flat band filling voltage, maximum ratio of NtN of the E1 center was achieved. This may indicate that the concentration of E1 centers, near the p+-n interface, can be larger than in the rest of the junction.