Structural and Optical Properties of Al Doped and Al Sandwiched ZnSe Thin Films رسالة ماجستير

Abstract

In the current study, Aluminum (Al) doping as well as Al nanosandwiching effects on the structural and optical properties of ZnSe thin films were investigated by means of X-ray diffraction and ultraviolet-visible light-near infrared spectrophotometry techniques, respectively. While the ZnSe doped with 13% Al revealed an amorphous nature of growth, the nanosandwiched films revealed a polycrystalline nature with structural properties that are sensitive to thickness of the sandwiched Al layer. Particularly, the lattice parameter of the cubic unit cell of the ZnSe increased significantly with increasing Al thickness. This increase in the lattice constant was associated with the increase in the grain size and decrease in the strain, dislocation density, and stacking faults. The remarkable enhancements in the crystallinity of the ZnSe that are associated with increasing Al thickness caused an engineering ability of the optical gap. Namely, the energy band gap decreased from 2.67 to 2.05 eV as the Al content increased from 0 to 100 nm. It was also observed that the increase in the Al thickness make band tails deeper. In addition, the analysis of the dielectric spectra has shown that the presence of 100 nm thick Al could increase the real part of the dielectric constant by three times, and increases the drift mobility from 65.6 cm2/Vs to 280.4 cm2/Vs .