Ivana Kovačević

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 (IO 2i ) 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.

UV light induced defects in amorphous silicon thin films

Abstract The effect of light soaking on a-Si:H films is well known as the Staebler–Wronski effect, though its complete mechanism is not yet clear. We have studied the effect of light soaking with UV light on intrinsic a-Si:H films, as well as the effect of thermal annealing in the dark. It is shown that the light soaking of the films in the air did not affect hydrogen concentration from Si–H bonds and at same time oxidation of the films is observed. It means that oxygen incorporation was due to broken back-bonds to Si–H which are very likely weak bonds. Moreover it is found that UV irradiation produced oxidation and caused even minor Si–H bond-breaking.

Defects induced in amorphous silicon thin films by light soaking

Abstract The effect of light soaking on a-Si:H films is well known as the Staebler–Wronski effect, though its complete mechanism is not yet clear. The effect of light soaking with UV and white light on intrinsic a-Si:H films was studied. It is shown that device quality a-Si:H films contain a considerable amount of oxygen. The light soaking of the films in the air affected differently low and high-hydrogen a-Si films. It was shown that deep levels in the gap introduced by light soaking are related to oxygen presence. The hydrogen present in the film differently influences the effects of light soaking as a function of its concentration.