Ab Initio Study Of ZnTe Semiconductor Alloys And The Thin Films Prepared

During the last decade, a considerable effort has been spent in the preparation and investigation of the family of II-VI wide-bandgaps’ semiconductors due to their fundamental electronic and optical properties. Among them, ZnTe, with a direct gap of 2.26eV at 300K, is an attractive material for various optoelectronic devices, such as green light-emitting diodes, electro-optic-field detectors and solar cells. In this paper, we studied the synthesis of polycrystalline thin films of ZnTe on conducting substrates (ITO-Sn:In2O3) by electrochemical method. And we also have demonstrated that the structure, composition and surface morphology depended on the solution’s Zn concentration.Unfortunately, ZnTe can be easily p-type doped but not n-type. The existence of the doping asymmetry problem has so far hindered the full utilization of ZnTe as a optoelectronic material. In this paper, we used state-of-the-art HSE06 functional calculations to demonstrate the possibility of ternary R(Sn,Pb)xZn1 ? xTe alloys’ bipolar-doping. The results show that the changes of bowing parameters and the band gaps of these alloys sensitively depend on the composition x. Wave functions’ full overlapping and localization of the Pb(Sn) outermost p orbits and Zn 4s orbits lead to a strong coupling between them, and then resulting in a significant downshift of conduction band edge with the increase of concentration x. When the concentration x reach 0.25, it is demonstrated that the conduction band edge of Pb0.25Zn0.75Te alloy has a substantial decrease, while the valence band edge kept almost unchanged, thus improving the possibility for ambipolar-doing. Meanwhile, the spectral response of this alloy (Eg =1.38 eV) is very consistent with the solar spectrum. We expect that our results will be helpful for the applications of optoelectronic devices.