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HL: Fachverband Halbleiterphysik

HL 63: II-VI-Compounds

HL 63.1: Talk

Wednesday, March 16, 2011, 15:45–16:00, POT 151

Band gap bowing of binary alloys: Experimental results compared to theoretical tight-binding supercell calculations for Cd_xZn_1−xSe — •Daniel Mourad¹, Gerd Czycholl¹, Carsten Kruse², Sebastian Klembt², Reiner Retzlaff², Detlef Hommel², Mariuca Gartner³, and Mihai Anastasescu³ — ¹Institut für Theoretische Physik, Universität Bremen — ²Institut für Festkörperphysik, Universität Bremen — ³Institute für Physikalische Chemie "Ilie Murgulescu", Rumänische Akademie

Compound semiconductor alloys of the type A_xB_1−xC find widespread applications as their electronic bulk band gap varies continuously with x, and therefore a tayloring of the energy gap is possible by variation of the concentration. We model the electronic properties of such semiconductor alloys by a multiband sp³ tight-binding model on a finite ensemble of supercells and determine the band gap of the alloy. This treatment allows for an intrinsic reproduction of band bowing effects as a function of the concentration x and is exact in the alloy-induced disorder. In the present talk, we concentrate on bulk Cd_xZn_1−xSe as a well-defined model system and give a careful analysis on the proper choice of the basis set and supercell size, as well as on the necessary number of realizations. The results are compared to experimental results obtained from ellipsometric measurements of Cd_xZn_1−xSe layers prepared by molecular beam epitaxy (MBE) and photoluminescence (PL) measurements on Cd_xZn_1−xSe nanowires reported in the literature.