The atomistic model of electronic properties of Al2O3 and ZnO for the calculations of Al-doped ZnO.

Abstract

The final aim of this work is to simulate the electronic properties of Al-doped ZnO (AZO). The density-functional theory with the Coulomb interaction potential (DFT+U) method was used to specify the electronic properties of wurtzite ZnO: band structure and the density of states. The tool for structural and electronic simulation was QuantumATK, produced by Synopsys. The first part of the simulation was based on the modeling of the wurtzite ZnO periodic cell, which consisted of 108 atoms. We tried to get reasonable value of the band structure, which is from 3.30 to 3.37 eV according to experiments. The implementation of the Hubbard U method requires setting up accurate energy values for localized atomic orbitals. These values will help to establish an estimate of the Al-doped ZnO parameters. The same process was applied to Al2O3-α (corundum) in the second step. Based on this procedure, we have obtained estimated energy values for the 2p orbital for oxygen, the 3p orbital for aluminum, and the 3d orbital for zinc. AZO is used in solar cells as a transparent conducting layer. The percentage of the aluminum doping in ZnO does change its electrical and optical properties. If we can succeed in finding the appropriate percentage of aluminum for the doped material in the model, we can compare it with the experiment and use it in the photovoltaic systems as a transparent conductive layer.