Nanoscale physics 

Defect structure and kinetic properties of CdSexTe1-x(x=0.1)  solid solution: ab initio calculation
Malyk O.P.1, Syrotyuk S.V.1
1 Semiconductor Electronics Department, Lviv Polytechnic National University. Bandera Street, 12, Lviv-79013, Ukraine. 
E-mail: omalyk@ukr.net
CdSexTe1-x possesses unique physical properties necessary for photovoltaic converters of solar energy, namely, a required band gap width and needed  absorption coefficient value. The optical and electrical properties of this material (in particular, the absorption coefficient and the transport phenomena) strongly depend on the structure of intrinsic and impurity point defects. Therefore, the study of the CdSexTe1-x defects structure is an actual applied problem. In literature there is a wide range of works where the ab initio approach is used to calculate the structure of defects. However, a common disadvantage of these works is the absence of connection between the structure of point defects and the kinetic characteristics, which determine the electronic properties of the material. In the proposed study the point defects in n-CdSe0.1Te0.9 are considered, namely: CdTe, CdSe, TeCd, SeCd, VTe, VSe, VTe–CdTe, VSe–CdSe. To calculate the energy spectrum of the ideal and defect structure the supercell method was used on the base of the ABINIT code. To establish the temperature dependence of the energy spectrum of an ideal and defect supercell an empirical formula for the temperature dependence of the band gap was used [1]. By choosing a mixture of the usual exchange-correlation GGA potential and the Hartree-Fock exchange potential a coincidence of experimental and theoretical values of the band gap was achieved at 0 and 300 K. The description of the transport phenomena in n-CdSe0.1Te0.9 was performed on the basis of short-range electron scattering models [2,3]. For crystals with defect concentration 11014 11018 cm-3 the temperature dependences of electron mobility and Hall factor in the range 15 – 400 K are calculated.

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