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Optical transitions near the band edge in bulk CuInxGa1−xSe2 from ellipsometric measurements |
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| Authors: | C. A. Durante Rinc n, E. Hern ndez, M. I. Alonso, M. Garriga, S. M. Wasim, C. Rinc n,M. Le n |
| Affiliation: | a Departamento de Física, Facultad Experimental de Ciencias, Universidad del Zulia, OPT Galerias, Aptdo. Postal 15645, Maracaibo, Venezuela b Institut de Ciència de Materials de Barcelona, CSIC, Campus de la UAB, 08193 Bellaterra, Spain c Centro de Estudios de Semiconductores, Facultad de Ciencias, Universidad de Los Andes, Mérida 5251, Venezuela d Departamento de Física Aplicada, Facultad de Ciencias, C-XII, Universidad Autónoma de Madrid, 28049 Madrid, Spain |
| Abstract: | From the analysis of the variation of optical absorption coefficient with incident photon energy between 0.8 and 2.6 eV, obtained from ellipsometric data, the energy EG of the fundamental absorption edge and EG′ of the forbidden direct transition for CuInxGa1−xSe2 alloys are estimated. The change in EG and the spin-orbit splitting ΔSO=EG′−EG with the composition x can be represented by parabolic expression of the form EG(x)=EG(0)+ax+bx2 and ΔSO(x)=ΔSO(0)+a′x+b′x2, respectively. b and b′ are called “bowing parameters”. Theoretical fit gives a=0.875 eV, b=0.198 eV, a′=0.341 eV and b′=−0.431 eV. The positive sign of b and negative sign of b′ are in agreement with the theoretical prediction of Wei and Zunger [Phys. Rev. B 39 (1989) 6279]. |
| Keywords: | Copper ternary alloys Ellipsometry Bandgap Forbidden direct transition Solar cells |
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