UNIFYING MODEL OF THERMAL AND LIGHT-INDUCED DEGRADATIONS OF A-SI-H

A model is presented with unifies the light-induced metastable behavior of a-Si:H (Staebler-Wronski effect) and the low-temperature H effusion through the same weak H site, activated by carrier recombination and by phonons, respectively. The unifying model is derived from the experimental data of Ohsawa et al., who found a correlation between metastability and weakly bonded H as determined by thermal H effusion. The proposed pathway for metastability, among others which may coexist, arises from the unstability of the site constituted by paired SiH bonds, which only need a low energy supply of about 1.5 eV for their concomitant rupture. The model also explains the site state reversibility by annealing and the fatigue of reversibility after consecutive annealings. © 1990.