Optical properties of the quaternary alloy system Culn(SxSe1−x)2 investigated by spectroscopic ellipsometry

Abstract

Experimental results for the pseudodielectric function 〈ε〉 of CuIn(SxSe1−x)2 alloy system are reported. The investigation has been performed on the full composition range using crystals cut from ingots of 10 mm diameter and 40 mm length. The ingots were grown using the classical Bridgman method. Ellipsometric measurements were performed at room temperature in the range 1.5–5.5 eV. The energies of critical points have been determined from the imaginary part of the dielectric function. The transition energies (E1, E2, E3, and E4) are found to shift linearly to higher energies as the sulfur content increases. The copper d level is found to be dominant in the ranges 2.5–3.5 eV for CuInSe2 and 2.8–4 eV for CuInS2.