Stability and band gaps of As‐rich and N‐rich GaAsN alloys: Density‐functional supercell calculations

Total energies and band gap energies of cubic cells with various arrangements of Ga32As32−nNn (n = 0–8 and n = 28–32 corresponding to 0.0–25.0% N and 12.5–0.0% As) are calculated using the density-functional supercell method. In the As-rich limit up to an exchange of 6.2% N isolated N atoms (maximum N distance) are the most stable arrangement and provide the typical reduction of the band gap energy from about 1.5 eV (GaAs) to about 1 eV caused by reduction of the N distance. For higher N content special N distributions are the most stable arrangements. GaNm clusters (m = 2–4) and isolated N atoms are less stable. The band gap remains nearly constant at about 1 eV between 6.2 and 18.8% N. The good agreement between the experimental band gap energies and ones calculated for the most stable arrangements points out that the experimental distribution of the atoms is the thermodynamic equilibrium distribution. In the N-rich limit, linear As chains in [110] direction or fragments of them are the most stable arrangement. At 9.4% As the band gap disappears. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)