Regensburg 2010 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 43: Electronic Structure and Atomistic Modeling
HL 43.4: Vortrag
Mittwoch, 24. März 2010, 14:45–15:00, H14
Tight-binding theory of CdxZn1−xSe semiconductor alloy nanocrystals — •Daniel Mourad and Gerd Czycholl — Institut für Theoretische Physik, Universität Bremen
For a wide class of semiconductor materials alloys of the type AxB1−x can be realized, e.g. CdxZn1−xSe, SixGe1−x, AlxGa1−xN, GaxIn1−xN, and many others. These substitutional alloys find widespread applications, in particular in nanoelectronic devices like quantum wells, quantum wires and quantum dots, as the band gap varies continuously with x, and therefore a band structure tayloring is possible by variation of the concentration. To calculate the electronic properties of such semiconductor alloys we start from multiband (sp3) tight-binding (TB) models for the pure bulk semiconductor materials A and B and perform ensemble averaged finite supercell calculations. Alternatively, we apply the coherent potential approximation (CPA) to calculate and compare the configurationally averaged electronic density of states and effective band structure. These treatments allow for an intrinsic reproduction of band bowing effects as a function of the concentration x and lead to finite lifetime effects due to the loss of translational invariance, contrary to much simpler mean-field approaches like the virtual crystal approximation (VCA). As an up-to-date application, we have in particular investigated CdxZn1−xSe nanocrystals. We compare our results to experimental ones by combining these treatments with the recently developed TB models of nanostructures. Finally, we discuss the proper choice of material parameters for these systems.