Instability effects in hydrogenated microcrystalline silicon thin films

Abstract

Instability effects on the dark conductivity (sigma(Dark)) and photoconductivity (sigma(photo)) of microcrystalline silicon films with different microstructures deposited on smooth and rough substrates, after exposure to different storage conditions have been investigated. Samples stored in vacuum are less affected by aging than films stored in air and sealed plastic bags filled with N-2 gas. The aging is reversible after annealing at 450 K. Thin films deposited on smooth and rough substrates with the same thickness and silane concentrations (SC) during the same deposition run showed similar aging effects. Thick samples exhibited a decrease in sigma(Dark), while both decrease and increase in sigma(Dark) occur in thin samples after aging. For each sample, sigma(Dark) and sigma(photo) presented the same type of aging, independent of thickness and type of substrate used. The applicability of the steady-state photocarrier grating technique was successfully tested on the rough substrates. Light-induced degradation studies confirm the dependence of the Staebler-Wronski effect on the crystallinity of the material. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim