Cluster Simulation of the Electronic Structure of Point Defects in the Ternary Semiconductor CuInSe2

We present results of cluster calculations by scattered wave method within framework of the embedded cluster model. Simulating a perfect crystal involved modelling fragments of [CuSe₄In₄]⁵⁺ and [SeCu₂In₂]⁶⁺ embedded in host-lattice “muffin-tin” potentials. In the simulation of a neutral Cu vacancy, we considered a V_CuSe₄In₄ cluster. The data indicate that the effect of the removal of Cu from the lattice gives rise to a level located ~ 40 meV above the top of the valence band. We calculated O and S impurities replacing Se in CIS. The main effect of inserting an impurity into the crystal was the narrowing of the valence band. The calculations show the domination of anti-site defects. The estimation about the relaxation of the CuInSe₂ lattice near structural defects was found.