Annealing-induced effects on the stability of hydrogenated amorphous silicon

SCHMIDT, J.A.; KOROPECKI, R.R.; ARCE, R.; BUITRAGO, R.H.

JOURNAL OF APPLIED PHYSICS

AMER INST PHYSICS

Año: 1995 vol. 78 p. 5959 - 5964

0021-8979

We performed isothermal annealing on a hydrogenated amorphous silicon (a-Si:H) sample deposited at low temperature in a glow discharge reactor. In order to change the hydrogen bonding configuration without affecting the silicon structure we choose a relatively low annealing temperature. We studied the dependence on the annealing time of the dark conductivity, photoconductivity, light-induced degradation of the photoconductivity, optical gap, vibrational spectra, and subgap defect density. As the annealing time increased we found an increase in the dark conductivity activation energy. This shift of the dark Fermi level toward the valence band was correlated with the growth of a peak in the density of states below midgap. From the vibrational spectra we obtained the microstructure parameter, which is indicative of the amount of hydrogen bonded as polihydrides and/or to some sort of internal surface. We used the bond-breaking model to fit photoconductivity decay as a function of illumination time, and we found a correlation between the Staebler-Wronski susceptibility and the microstructure parameter. This would mean that the stability of the material concerning light-induced degradation is related to the way hydrogen is attached in the amorphous network. © 1995 American Institute of Physics.