Effect of hydrogen on the density of gap states in reactively sputtered amorphous silicon

The density of states near midgap and the hydrogen content have been measured on a number of reactively sputtered $a-\mathrm{Si}{\mathrm{H}}_x$ films prepared at different hydrogen partial pressures. The density of states near midgap is observed to decrease exponentially with increasing hydrogen partial pressure to less than ${10}^{15}$ states ${\mathrm{cm}}^{-3\mathrm{}}$ e${\mathrm{V}}^{-1\mathrm{}}$. The data are interpreted in terms of a simple kinetic model of the H incorporation in the $a-\mathrm{S}\mathrm{i}$ network.