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