Electric-field-enhanced emission and annealing behaviour of electron traps introduced in n-Si by low-energy He ion bombardment

The isochronal annealing and electric-field-enhanced emission properties of three defects (EHe203, EHe584 and EHe211), observed in low-energy He-ion bombarded n-Si, were studied using deep level transient spectroscopy. EHe203 (E_C - 0.20 eV) and EHe584 (E_C - 0.58 eV) were thermally stable up to ∼400°C after which their removal was accompanied by the introduction of a secondary defect EHe211 (E_C - 0.21 eV). EHe211 was thermally stable at 650°C. The emission rate of EHe203 was significant for electric fields above 4 × 10⁴ V cm^-1, and was enhanced by over 3 orders of magnitude for a corresponding three-fold increase in electric field. The emission rate of EHe211 was only weakly field dependent over the electric field range studied, while that of EHe584 remained constant for electric fields between 3 × 10⁴ and 9 × 10⁴ V cm^-1. EHe584 has been proposed to be an acceptor-type defect. It was found that square wells of radii 57 Å and 40 Å described the potentials induced by EHe203 and EHe211, respectively, reasonably well. Alternatively, Gaussian potential wells with α = 20 Å and V₀ = 0.30 eV (EHe203) and α = 12 Å and V₀ = 0.35 eV (EHe211) could be used to fit our experimental data.