Theoretical and experimental investigations of the structural and optoelectronic properties of Zn1−xCdxO alloys

Abstract

In this work, we report theoretical and experimental studies on the structural, electronic and optical properties of wurtzite Zn1−xCdxO alloys. The theoretical investigations were conducted using the density functional theory (DFT) as implemented in the Wien2k package which is based on the full potential linearized augmented plane wave (FPLAPW). The modified exchange potential proposed by Becke-Johson (mBJ) with local gradient generalized approximation (GGA) was used in this study. The lattice parameters, electronic structure and optical properties were studied in details for the composition x of cadmium 0, 0.16, 0.25, and 0.33. Experimentally, Zn1−xCdxO alloys were grown by the sol–gel spin coating method with different cadmium concentrations specifically x = 0, 0.10, 0.20, and 0.30. The obtained experimental results were systematically analyzed and compared with the DFT calculations. From the theoretical findings, it is noticed that the structural and electronic properties of Zn1−xCdxO are strongly affected by the Cd doping amount. The lattice parameters increase and the band gaps decrease with the x fraction of cadmium showing a quantitative agreement with the experimental results. Moreover, the investigation of the total and partial density of the Zn1−xCdxO alloy for the different bands reveals that the optical transition between O-2p states in the top of valence band and Zn-4s states in the bottom of the conduction band is shifted to lower energy range as the Cd concentration increases. In addition, the dielectric function, the absorption coefficient, and the refractive index and discussed for the different cadmium composition. Combining both theoretical calculations on Zn1−xCdxO alloys with the obtained experimental results provides better understanding of the physical properties dependence on the composition and would help to engineer such alloys for high performance optoelectronic and nonlinear optical devices.