Electronic and dynamical properties of the silicon trivacancy

Abstract

The trivacancy (V 3) in silicon has been recently shown to be a bistable center in the neutral charge state, with a fourfold-coordinated configuration, V 3[FFC], lower in energy than the (110) planar one. Transformations of the V 3 defect between different configurations, its diffusion, and disappearance upon isochronal and isothermal annealing of electron-irradiated Si:O crystals are reported from joint deep level transient spectroscopy measurements and first-principles density-functional calculations. Activation energies and respective mechanisms for V 3 transformation from the (110) planar configuration to the fourfold-coordinated structure have been determined. The annealing studies demonstrate that V 3 is mobile in Si at T>200C and in oxygen-rich material can be trapped by interstitial oxygen atoms so resulting in the appearance of V 3O complexes. The calculations suggest that V 3 motion takes place via consecutive FFC/planar transformation steps. The activation energy for the long-range diffusion of the V 3 center has been derived and agrees with atomic motion barrier from the calculations. © 2012 American Physical Society

Investigation of point and extended defects in electron irradiated silicon—Dependence on the particle energy

“…As shown in the literature, this defect is bi-stable, changing its configuration at ambient temperatures from a PHR configuration to a fourfold coordinated (FFC) one, 30 while it is stable up to 220 C. 32,33 It has been shown previously that the recovery of both DLTS signals (from V 3 ¼/À and V 3 À/0 ) is possible by injection of a high forward current (1 A at 20 C for 10 min). 28,30,31 If the V 3 defect is partly responsible for the leakage current, then both the leakage current and the defect concentration should have also a similar annealing behavior.…”

“…Among the multitude of radiation induced electrically active defects only some proved to have a direct impact on the "macroscopic" behavior of the sensors operating at ambient temperatures. These point-or extended-defects are labeled in the literature as: I p -a deep acceptor strongly generated in oxygen lean, standard float-zone material (STFZ) [22][23][24] and BD-a bistable thermal donor (TDD2) 24,26,27 strongly generated in oxygen rich float-zone material (DOFZ), both associated with point defects that are stable at room temperature and determining the N eff in silicon diodes irradiated with Co 60 g-rays; E(30K)-a shallow donor contributing to the a) R. Radu beneficial annealing after hadron irradiation, strongly generated in diodes irradiated with charged particles; 10,29 H(116K), H(140K), H(152K)-cluster-related hole traps with enhanced field emission (acceptors in the lower part of the Si bandgap), contributing fully with their concentration to N eff and causing the long term annealing effects (reverse annealing) in hadron irradiated silicon diodes; 10,29 the bistable E4 and E5 energy levels-identified with the double and single acceptor charge state of the V 3 defect in a configuration part of a hexagonal ring (PHR), respectively, [30][31][32][33] a defect contributing to the magnitude of the leakage current in the Si sensors and bipolar transistors upon irradiation with high energy particles. 28,31 The most important characteristics of these defects, including some features resulted from the present work, are summarized in Table I.…”

In-growth of an electrically active defect in high-purity silicon after proton irradiation

“…Besides, the change of the di-vacancy concentration when the AU defect grows in is small compared to the change of the AU defect which suggests that the di-vacancy is not involved in the AU defect. Recent reports on the tri-vacancy in silicon 23,24 have shown that this defect is a bistable defect which has two donor levels in the lower half of the band gap at E V þ 0.106 eV and E V þ 0.193 eV, and that it becomes mobile at temperatures higher than 200 C. These observations exclude that the AU defect is related to the tri-vacancy. Thus, this discussion of vacancy defects points towards an AU defect which does not include vacancies.…”

Electron and Proton Irradiation of Silicon

“…Recently, Markevich and coworkers published a number of papers combining DLTS investigations and density-functional modeling calculations (Coutinho et al, 2012;Markevich et al, 2009), and they have been able to describe the structure of the trivacancy and to establish its energy-level structure in the band gap. Markevich et al (2009) andCoutinho et al (2012) found that the trivacancy is a bistable center in the neutral charge state, and that the fourfold coordinated (FFC) configuration shown in Fig. 21D is the ground state, whereas V 3 is metastable by 0.26 eV in the (110)-planar configuration (the part of hexagonal ring (PHR) structure) shown in Fig.…”

“…Intermediate structures along the mechanism are shown in (B) and (C). Broken bonds are shown as solid sticks (red sticks in the online version), reconstructed radical pairs Si i -Si i 0 are shown as "banana" bonds, and Si atoms that are slightly perturbed (or unperturbed) from their lattice sites are shown in white (Coutinho et al, 2012). Reproduced with permission from the American Physical Society.…”