Theory of Anion-Substituted Nitrogen-Bearing III-V Alloys

Because of the large bond-length mismatch between N and P or As, enormous internal strains strongly inhibit the miscibility of the latter into the anion lattice. This final report discusses the expected thermodynamic behavior of incorporation of P or As into the III-N lattice, by calculating the miscibility gaps in the regular solution model. The band states show some remarkable behavior when small amounts of phosphorous or arsenic are substituted for nitrogen. For example, when 1 As is substituted into GaN, a state is introduced into the gap at about 0.2 eV above the valence band edge 0.8 eV was found by Zunger group. When more than 4 arsenic is incorporated into GaN in an ordered array, the band gap closes. Calculations of the properties of random alloys predict smaller bowing than do the ordered alloy calculations. Hole lifetimes in GaAs0.1N0.9 are predicted to be quite low, of the order of 10exp -14 sec.