Vacancy-related complexes in neutron-irradiated silicon

Electrically active defects induced by neutron irradiation in n-type Czochralski-grown (Cz) Si crystals have been studied by means of capacitance transient techniques. These neutron-induced defects are compared with those created by electron irradiation and self-ion implantation. Four electron traps with the activation energies for electron emission of 0.12, 0.16, 0.24 and 0.42 eV were observed after neutron irradiation in phosphorous-doped Cz Si crystals. It is inferred that the E(0.12) and E(0.16) traps are related to the single-acceptor states of the silicon self-interstitial-oxygen dimer complex (IO2i) and the vacancy-oxygen pair (VO), respectively. The E(0.24) trap is associated with the electron emission from the double-acceptor state of the divacancy (V-2). However, an asymmetric peak with its maximum at around 220 K and an activation energy for electron emission of 0.42 eV dominated the spectra. We used high resolution Laplace DLTS to investigate the structure of E(0.42) and found that this signal is complex, consisting of contributions from several defects. From the annealing behaviour, it was revealed that as some of these defects anneal out they are sources of vacancies evidenced by an increase in the concentration of VO and V-2. It is suggested that some of the defects contributing to the E(0.42) peak are related to small vacancy clusters.