Temperature dependence of the thermal-equilibrium defect density in undoped a-Si:H, a-${\mathrm{Si}}_{1\mathrm{-}\mathit{x}}$${\mathrm{C}}_{\mathit{x}}$:H, and a-${\mathrm{Si}}_{1\mathrm{-}\mathit{x}}$${\mathrm{N}}_{\mathit{x}}$:H is obtained both by in situ electron-spin-resonance (ESR) measurements at elevated temperatures and by ESR measurements of frozen-in defects at room temperature. The experimental results confirm that the defects in these alloy films, even for films with the defect density as high as ${10}^{17}$ ${\mathrm{cm}}^{\mathrm{-}3}$, can reach thermal equilibrium above a certain temperature (200–350 °C). Thickness dependence of the defect density after various thermal treatments shows that only the bulk defect density increases with temperature, with the exception that thin a-Si:H films (<1 μm) exhibit some extra increase. Results of ESR, light-induced ESR (LESR), and constant-photocurrent method (CPM) measurements indicate that the charged-defect density in these films does not appreciably increase with temperature. Relaxation of the frozen-in defect density follows a stretched exponential form and the relaxation time increases with the defect density in these alloys.

• Received 20 October 1989

DOI:https://doi.org/10.1103/PhysRevB.41.10049