Metastability of hydrogenated amorphous silicon

✍ Scribed by Jacques I. Pankove

• Publisher: Elsevier Science
• Year: 1987
• Weight: 514 KB
• Volume: 21
• Category: Article
• ISSN: 0379-6787
• DOI: 10.1016/0379-6787(87)90140-2

✦ Synopsis

The metastability of hydrogenated amorphous silicon engenders many measureable effects: changes in the dark conductivity and photoconductivity (Staebler-Wronski effect); reduced luminescence efficiency but enhanced emission at approximately 0.8 eV; increased spin resonance due to silicon dangling bonds; changes in optically detected magnetic resonance; increased sub-band-gap absorption; reduced pT product; increased small-angle neutron scattering; changes in deep level transient spectroscopy. The metastable effects can be induced by visible light, by X-rays, by electron or ion bombardment, by anbipolar injection and even by single carrier injection (more strongly by hole injection). All these effects can be reversed by thermal annealing between 150 and 200 °C. A few reports indicate that solar cell improvement can be obtained by irradiation with intense light with or without applied electric field. Two models explain most of the observations: (1) the breaking of weak Si--Si bonds by the energy released during pair recombination or during carrier trapping and (2) a charge redistribution between already existing dangling bonds.