Amorphous Phase Influence on the Optical Bandgap of Polysilicon

EMA is a method to estimate the dielectric response of a compound material [1]. We study a nanocrystalline film compound manufactured under highly nonequilibrium conditions, composed of crystalline silicon, c-Si, amorphous silicon, a-Si, and voids. The structure of crystalline silicon can be modified by introducing amorphous silicon. So, the optical properties can be changed because another phase in the crystalline silicon introduces disorder. From the Bruggeman formula the refractive index (n) and absorption index (k) of the mixture can be calculated if the values of n and k for the material components are known. The k spectra versus energy ( hw) or wavelength (l 1= hw) give information about the value of the optical bandgap of polysilicon. The aim of this paper is to analyze the optical properties (energy bandgap) of polycrystalline silicon for different percentages of a-Si and c-Si.