Modification of the Electronic and Optical Properties of As2Te3 Upon Copper Doping

β-As₂Te₃ which is isostructural to topological insulator Bi₂Te₃, has been doped with copper in order to investigate the effect of the addition of charge carriers on the optical properties and electronic structure. The plasma edge in the MIR reflectance undergoes a blue shift to higher energy with increasing copper. The Drude fit parameters suggest that distinct mechanisms may exist for the doping in different regimes.