The theoretical results provide comprehensive understanding for recent experimental observations on the shift of the absorption energy assigned to E1 direct transitions within L and Γ points in the Brillouin zone of Si1-xGex alloy nanocrystals. | VNU Journal of Science: Mathematics – Physics, Vol. 32, No. 4 (2016) 57-62 Tuning the Electronic Structure of Si1-xGex Alloys Tran Van Quang1,*, Nguyen Truong Giang1,2, Ngo Ngoc Ha2 1 Department of Physics, University of Transport and Communications, No. 3 Lang Thuong, Hanoi, Vietnam 2 International Training Institute for Materials Science, Hanoi University of Science and Technology, Hanoi, Vietnam Received 20 October 2016 Revised 16 November 2016; Accepted 28 December 2016 Abstract: Binary alloys of Si1−xGex, where x is the Ge composition, have attracted much attention as functional materials of both micro-electronic and opto-electronic devices in recent years. In this study, we employ first-principles density functional theory (DFT) and method to study ground states of the SixGe1-x (x = 0 1) alloys. In the systems, most physical properties of the indirect semiconductors are retained which are principally described by the ground states. An interesting property of Si1−xGex alloys that is their electronic band structures are tunable between those of bulk Si and Ge. The conduction band minimum of Si shifts gently from a point along ΓX path to the L point with the increased Ge composition x. The band structures of Si1-xGex alloys calculated by the method are consistent with the results from DFT calculations. We also find that band topology changes along ΓL path yield various quantum transitions which may give rise to the changes of external quantum efficiency. The theoretical results provide comprehensive understanding for recent experimental observations on the shift of the absorption energy assigned to E1 direct transitions within L and Γ points in the Brillouin zone of Si1-xGex alloy nanocrystals. Keywords: Si-Ge alloy nanocrystals, electronic structure, and ground state, functional theory. density 1. Introduction Forming from the two typical indirect semiconductors in group IV of the periodic table, Si 1−xGex (x = 0 1) alloys have attracted much .
