Experimental and theoretical aspects of electric-field-assisted positron kinetics in metal-oxide-silicon systems - art. no. 045322

摘要

We use positron annihilation spectroscopy to study positron kinetics in electrically biased metal-oxide-silicon (MOS) system and trapping at the SiO2/Si interface. Experiments carried out on samples with an extra thick (1 mum) oxide layer reveal the electric-field-assisted positron transport in the oxide, and bring supportive evidence for the two-defect-state trapping model of the SiO2/Si interface. The time-dependent drift-diffusion equation was solved for oxide-implanted positrons in order to obtain the fractions of positrons annihilating in the oxide and its interfaces. By fitting these results to the experimental data, the positron mobility was calculated to be mu(+)=1.20+/-0.09 cm(2)/V s. This value is two orders of magnitude larger than that previously reported by Kong [J. Appl. Phys. 70, 2874 (1991)], indicating distinct oxide properties. We address the mutually contradictory existing theoretical models, revise the present understanding of the positron behavior in MOS systems, and propose a general interpretation of available results from the literature. [References: 26]