Electronic_Structure

Chandrima Mitra, Graduate Student Session D40: Semiconductors: Electronic Structure

2:30 PM–5:30 PM, Monday, March 5, 2007
Colorado Convention Center - 503

Sponsoring Unit: FIAP
Chair: Hai Ping Cheng, University of Florida

Abstract ID: BAPS.2007.MAR.D40.8

Abstract: D40.00008 : Large band gap bowing in CuAgGaS2 chalcopyrite semiconductors and its effect on optical parameters

3:54 PM–4:06 PM

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Authors:

Chandrima Mitra
(Case Western Reserve University, Department of Physics)

Walter Lambrecht
(Case Western University, Department of physics)

CuxAg$_{1-x}$GaS$_2$ chalcopyrite semiconductors have been found to exhibit a large band gap bowing. Here we use full-potential linearized muffin-tin orbital calculations in the local density approximation of density functional theory to study the electronic band structure of these materials. The randomness in the alloy is treated by the special quasirandom structures. Some layered ordered compounds are studied as well. We find the band gap to depend strongly on the c/a ratio which varies nonlinearly with concentration, in agreement with experimental data by Matsushita et al. The bowing coefficient is found to be 0.74. We also calculate the indices of refraction and their dependence on concentration. Band gap corrections are adjusted using direct shifts to the conduction bands and adjusted for the end compounds. We find that the nonlinear behaviour of the band gap also leads to a non-linear behaviour of the index of refraction with x.

Tula R. Paudel, Graduate Student

Session D40: Semiconductors: Electronic Structure

2:30 PM–5:30 PM, Monday, March 5, 2007
Colorado Convention Center - 503

Sponsoring Unit: FIAP
Chair: Hai Ping Cheng, University of Florida

Abstract ID: BAPS.2007.MAR.D40.14

Abstract: D40.00014 : Structure, Electronic Structure and Phonons of ZnSnN2

5:06 PM–5:18 PM

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Authors:

Tula R. Paudel
(Case Western Reserve University )

Walter R. L. Lambrecht
(Case Western Reserve University )

The structure and electronic structure of ZnSnN$_2$ was calculated using density functional theory in the local density density approximation (LDA) and the linearized muffin-tin orbital method (LMTO). The wurtzite lattice constant is found to be slightly greater then that of GaN. The system is found to have small direct band gap of 0.07eV at $\Gamma$ in LDA. The phonon frequencies at the $\Gamma$ were calculated by linear response theory and were labeled according to the symmetry. To the best of our knowledge this compound is studied for the first time both experimentally and theoretically. The stability of the compound will be discussed and the structural electronic and vibrational properties will be compared with other members of the Zn-IV-N$_2$ (IV=Si,Ge) compounds.

Please send comments and suggestions to paul.larson@case.edu