Light-induced defect densities in hydrogenated and deuterated amorphous silicon deposited at different substrate temperatures.

Abstract

The saturated metastable defect density under AM1 (100 mW ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$) illumination as well as their formation and annealing kinetics have been studied in a large number of hydrogenated, and deuterated amorphous silicon films, prepared by plasma enhanced chemical-vapor deposition of silane at substrate temperatures of 250 \ifmmode^\circ\else\textdegree\fi{}C--450 \ifmmode^\circ\else\textdegree\fi{}C at different deposition rates, having low stable defect densities. The hydrogenated films exhibit a characteristic saturated defect density of (2--5)\ifmmode\times\else\texttimes\fi{}${10}^{16}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$ independent of deposition conditions. There is no variation in the formation or annealing kinetics for samples with initial defect densities 3\ifmmode\times\else\texttimes\fi{}${10}^{15}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$, but samples with higher initial defect densities have an order-of-magnitude longer time constants. On the other hand, there is a marked reduction of the saturated defect density in the deuterated films when the deposition temperature is increased even though the kinetics are similar to their hydrogenated counterparts. This shows that the saturated metastable defect density can be varied but is not a simple consequence of the average sample properties or the defect kinetics.