Open Access Special Issue Article

On the Chemical Origin of the Gap Bowing in (GaAs)1−xGe2x Alloys: A Combined DFT–QSGW Study

Giacomo Giorgi1*, Mark Van Schilfgaarde2, Anatoli Korkin2 and Koichi Yamashita1

Author Affiliations

1 Department of Chemical System Engineering, School of Engineering, University of Tokyo, Tokyo, 113-8656, Japan

2 Arizona State University, Tempe, AZ, 85287, USA

For all author emails, please log on.

Nanoscale Research Letters 2010, 5:469-477  doi:10.1007/s11671-009-9516-2

Published: 7 January 2010

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)1xGe2x series of alloys. We have investigated the structural properties of some (GaAs)1xGe2x 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