Berlin 2012 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 98: Electronic Structure Theory
HL 98.11: Vortrag
Freitag, 30. März 2012, 12:15–12:30, EW 202
Extracting an effective band structure from supercell calculations on alloys and impurities: Evolution of the impurity band with clustering in GaN:P — •Voicu Popescu1,2 and Alex Zunger3 — 1Faculty of Physics, University Duisburg-Essen, 47048 Duisburg, Germany — 2Colorado School of Mines, Golden, Colorado 80401, USA — 3University of Colorado, Boulder, Colorado 80302, USA
While the supercell approach to defects and alloys enables to circumvent the limitations of those methods that insist on using artificially high symmetry, this step usually comes at the cost of abandoning the language of E versus k→ band dispersion. We describe a computational method that maps the energy eigenvalues obtained from large supercell calculations into an effective band structure (EBS) and recovers an approximate E(k→) for alloys. Making use of supercells allows one to model a random alloy A1−xBxC by occupying the sites A and B via a coin-toss procedure affording many different local environments to occur (polymorphic description). We present the supercell EBS methodology and apply it to study the evolution of the impurity band appearing in the dilute GaN:P alloy. We treat both the perfectly random case as well as the non-random microstructures formation, and investigate how their appearance is reflected in the EBS. It turns out that the EBS is extremely sensitive in determining the critical disorder level for which delocalised states start to appear in the intermediate band. In addition, the EBS allows us to identify the role played by atomic relaxation in the positioning of the impurity levels.