Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: On the Chemical Origin of the Gap Bowing in (GaAs)12xGe2x Alloys: A Combined DFT–QSGW Stud | Nanoscale Res Lett 2010 5 469-477 DOI s11671-009-9516-2 SPECIAL ISSUE ARTICLE On the Chemical Origin of the Gap Bowing in GaAs 1_xGe2x Alloys A Combined DFT-QSGW Study Giacomo Giorgi Mark Van Schilfgaarde Anatoli Korkin Koichi Yamashita Received 20 November 2009 Accepted 17 December 2009 Published online 7 January 2010 The Author s 2010. This article is published with open access at Abstract Motivated by the research and analysis of new materials for photovoltaics and by the possibility of tailoring their optical properties for improved solar energy conversion we have focused our attention on the GaAs 1_xGe2x series of alloys. We have investigated the structural properties of some GaAs 1_xGe2x compounds within the local-density approximation to density-functional theory and their optical properties within the Quasiparticle Self-consistent GW approximation. The QSGW results confirm the experimental evidence of asymmetric bandgap bowing. It is explained in terms of violations of the octet rule as well as in terms of the order-disorder phase transition. Keywords Photovoltaics III-V IV-doped alloys Bandgap bowing Order-disorder phase transition DFT Quasiparticle Self-consistent GW Introduction The design of semiconductors with controlled bandgaps EG unit cell parameters and low defect concentration is the ultimate aim in several important areas of industrial applications electronics photonics light-emitting devices and photovoltaics PV . Efficient collection of solar energy requires materials that absorb light from different G. Giorgi El K. Yamashita Department of Chemical System Engineering School of Engineering University of Tokyo Tokyo 113-8656 Japan e-mail giacomo@ M. Van Schilfgaarde A. Korkin Arizona State University Tempe AZ 85287 USA portions of the solar spectrum followed by efficient conversion into electrons and holes at p-n junctions. A natural approach to the design of new semiconductors is to alloy two materials
