Electrical properties of annealed a-SiC:H thin films

Abstract

In the present work the dependence of electrical properties of a-SiC:H thin films on annealing temperature, Ta, has been extensively studied. From the measurements of dark dc electrical conductivity, σD, in the high temperature range (from 283 up to 493K), was found that the conductivity activation energy, Ea, is invariant for Ta⩽673K and equal to 0.64eV, whereas for Ta from 673 up to 873K, Ea increases at about 0.2eV reaching to a maximum value 0.85eV at Ta=873K, suggesting the optimum material quality. This behavior of Ea as a function of Ta is mainly attributed to relaxation of the strain in the amorphous network, which is possibly combined with weak hydrogen emission for temperatures up to 873K. For further increase of Ta (>873K) the phenomenon of hydrogen emission, causes rapid decrease of Ea down to 0.24eV at Ta=998K, deteriorating the material quality. These results are also supported by the measurements of dark dc electrical conductivity in the low temperature range (from 133 up to 283K), where the dependence of the density of gap states at the Fermi level, N(EF), on annealing temperature presents the minimum value at Ta=873K. The Meyer–Nelder rule was found to hold for the a-SiC:H thin films for annealing temperatures up to 873K. Finally, the dependence of dark dc electrical conductivity at room temperature, σDRT, on Ta showed to reflect directly the dependence of Ea on Ta.