Determination and analysis of optical constants for Ga 2Se 3 films near absorption edge

Abstract

Ga 2Se 3 has been prepared in bulk and thin film forms. The composition of films has been checked using energy dispersive X-ray spectroscopy technique. X-ray diffraction measurements have shown that Ga 2Se 3 films evaporated at room temperature substrates were amorphous. The transmittance ( T) of Ga 2Se 3 thin films has been measured over the wavelength range (400– 900 nm ). The optical constants, the refractive index ( n) and the absorption index ( k) have been determined from the analysis of the transmittance data. Analysis of the refractive index ( n) yields the values of the long wavelength dielectric constant ( ε ∞), the average oscillator wavelength ( λ o), average oscillator strength ( S o), average oscillator energy E o, the refractive index dispersion parameter ( E o/ S o) and the dispersion energy ( E d). Analysis of absorption index ( k) yields both direct and indirect allowed transitions with optical energy gaps of 2.65 and 2.056 eV , respectively. The effect of annealing at different temperatures on optical constants is also investigated.