A study of interface state density between a-Si:H and insulating layer in terms of plasma surface reaction

Abstract

We investigated the correlation between source gas and interface defects during film growth of an insulating layer on the surface of a-Si:H. The interface defect density was measured by photothermal deflection spectroscopy and electron spin resonance. We found that the interface defect density depends on the partial pressure or the gas ratio during deposition of the insulating layer. The interface defect densities in a-SiN x :H/a-Si:H and a-SiO x :H/a-Si:H structures increased with increasing x. The interface defect density at the largest x in a-SiN x :H and a-SiO x :H structures was similar to the case of the surface treatment of a-Si:H by NH 3 and N 2O plasma, respectively. A large difference in the induced defect density was observed by the plasma treatment with diluted N 2O gas depending on diluted gas species. These results suggest that the reaction of a-Si:H surface with the source gases during the deposition of an insulating layer was essential for the formation of interface defects. Since the composition, x, was controlled by the source gas ratio, the change in the interface defect densities with x corresponded to the change in plasma species in the source gas.