Stability and band gaps of InGaAs, BGaAs, and BInGaAs alloys: Density-functional supercell calculations

摘要

The influence of arrangement and content of substituents (B, In) in BGaAs, InGaAs, and BInGaAs alloys on the stabilities and band gaps is investigated using density-functional supercell calculations. The stability of ternary alloys decreases from InGaAs over BGaAs to GaAsN. Typical substituent structures show the following stability order: isolated substituents - [110] chains - clusters - twisted [111] chains (200/211) arrangements (most stable). This is valid for both the In- and B-poor as well as the In- and B-rich alloys. From the fact that grown InGaAs provides a different gap than the most stable arrangement one can conclude that other structures (isolated indium atoms or InmAs clusters) are formed during the growth. Simultaneous substitutions (BInGaAs) of larger (In) and smaller (B) atoms prefer arrangements in larger distances (220) for isovalent boron substitution and in In-B bonds for antisite boron substitution. The high degree boron antisite substitution induces partially occupied acceptor bands which lead to a strong reduction of the band gap in comparison to the isovalent substitution. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.