Optical properties and electronic structure of polycrystalline Cu-(In Ga)-Se alloys

Abstract

The optical properties of bulk Cu-(In Ga )-Se alloys grown by the Bridgman metho are presented. The optical measurements were performed at room temperature in the photo energy range from 0.8 to 4.7eV using a variable-angle spectroscopic ellipsometer. The spec tral dependences of the complex dielectric function, the refractive index, the absorption coe ficient and the normal-incidence reflectivity were derived. The observed structures attribute to the interband transitions E0 , E1A , and E1B were modelled using a modification of the Ada chi’s model. The model parameters were determined using the simulated annealing (SA) algo rithm. The values of E0 and E1A were found to increase linearly with Ga content.