Approach to study the relation between optical energy gap and hydrogen concentration in hydrogenated amorphous silicon thin films

Using experimental plasmon loss energy of a-Si the number of valence electrons per unit volume in amorphous silicon thin films is determined. The characteristics of hydrogen incorporation in silicon network is studied by a quantitative model assuming that the structure of a good quality a-Si:H thin film dominantly consists of Si-H and Si-Si bonds only. Using the concept of Penn gap and bond polarizability, we have derived an expression for the optical energy gap as a function of hydrogen concentration for a-Si:H thin films. The calculated results, thus, obtained agree very well with the experimental results.