THE EFFECT OF HYDROGEN CONCENTRATION ON REFRACTIVE INDEX AND OPTICAL GAP IN HYDROGENATED AMORPHOUS SILICON

The optical properties of a-Si:H have been measured by several workers but there has been no suitable model to explain these results. A quantitative model for the incorporation of hydrogen in aSi:H network to introduce hydrogen dependency of the optical properties has been developed. The concept of bond polarizabilities has been used to compute refractive index of a-Si:H as a function of hydrogen concentration. The results obtained have been compared with recent experimental results and the discrepancy has been explained. It has been found that the optical gap (Eg) increases with the increase of hydrogen concentration (CH). The results have been found to be consistent with the recent experimental results. Other results have also been compared and a theoretical relation Eg = 1.5 + 1.2 CH is thus obtained which corresponds reasonably well with the experimental results.