Abstract
We report theoretical calculations of the electronic band structure and surface states of Cu-chalcopyrite semiconductors. The systems under consideration are CuGaS2, CuAlSe2, and CuGaS2 doped with Cr. The calculations are carried out using semi-empirical Tight-Binding formalism. By reproducing the band gap of these systems obtained by ab-initio calculations we report the Tight-Binding parameters required for the band structure calculations. We present bulk band structure calculations of the above mentioned semiconductors, and we analyze the (001) and (110) surface states of the corresponding semi-infinite semiconductors.
Highlights
Chalcopyrite crystals derived from the I-III-VI2 (I = Cu, III = Ga, Al, and VI = S, Se) family have received considerable attention as one of the promising materials to be used for thin film solar cells fabrication [ 1-3]
The band gap range from 1.7 eVfor CuGaSe2, i.e. from the deep red, to 2.43 for CuGaS2, and to 2.65 eVfor CuAlSe2, with its main absorption peak located near ultra-violet (UV) region [4,5,6,7,8,9]
In this paper we present a TB study ofthe electronic band structure ofthe CuGaS2, CuAlSe2 chalcopyrite semiconductors, together with the corresponding material CuGaS2 doped with Cr in order to obtain an intermediate band
Summary
As a main goal ofthis paper we adjust all the necessary TB parameters to reproduce the values ofthe band gap experimentally documented as well as the main features ofthe band structure obtained from ab-initio first-principles calculations recently reported. Using these parameters, we calculate the electronic band structure ofthe above mentioned chalcopyrite semiconductors along the principal directions ofthe corresponding Brillouin zone. This last analysis is carried out by using the Surface Green Function Matching (SGFM) method, which is a successful technique employed to calculate the electronic properties of surfaces, interfaces, quantum wells, and superlattices [28,29]
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