A.S.Ferlauto, Joohyun Koh, P.I. Rovira, C.R. Wronski, R.W. Collins, Gautam Ganguly
We describe simple expressions that use a minimum number of free parameters to fit the dielectric function spectra of a variety of Si-based film materials ranging from amorphous silicon (a-Si:H) and its alloys with Ge and C to nanocrystalline silicon (nc-Si:H) and microcrystalline silicon (μc-Si:H). Three applications of these formulas are presented. First, we demonstrate how the expressions can be used in optical modeling of multijunction solar cells. Second, we analyze a-Si:H materials prepared versus the H2-dilution flow ratio, R=[H2]/[SiH4], and observe that improved ordering is obtained at larger R. Finally, we analyze Si films as a function of thickness across the a→μc phase boundary and quantify effects of electronic confinement in the nc-Si:H regime and grain development in the μc-Si:H regime.