Defect equilibration and metastability in low-spin-density amorphous hydrogenated silicon

Electron spin resonance was used to characterize concentrations of thermal equilibrium defects from room temperature to 280 °C in a 60 μm thick hydrogenated amorphous silicon film. A defect formation energy of 0.35 eV was found in material with $\text{1×10}{}^{15}\text{cm}{}^{\mathrm{-3}}$ spins at 190 °C. Annealing of defects quenched in from 250 °C revealed an activation energy of 2.2 eV. Annealings at 150 °C of defects quenched in at 250 °C and 190 °C were compared; the additional defects introduced at the higher temperature annealed 10 times faster, supporting a model in which metastable states with higher formation energies have smaller annealing activation energies. Light-induced defects are described in terms of a very “high-temperature” distribution similar to that which might be quenched in as a result of $\text{kT ≈ 0.5}\text{eV}$.