Thermal stability of the optical band gap and structural order in hot-wire-deposited amorphous silicon

Abstract

The material properties of hydrogenated amorphous silicon (a-Si:H) have been known to change when exposed to elevated temperatures. In this work researchers report on the thermal stability of the optical band gap and structural disorder in hot-wire deposited a-Si:H with different hydrogen concentrations. Furthermore, the changes in the structural disorder will be correlated with the changes in the optical band gap. Raman spectroscopy shows evidence that no crystallization is induced at 450 °C and that the structural disorder increases upon annealing. The increase in the structural disorder results in a broadening of the valence and conduction band tails, thereby pinning the valence and conduction band edges closer together, resulting in a decrease in the optical band gap as probed by optical reflection and transmission measurements.