An investigation was made, of the basic properties of F atoms, by using first-principles calculations. It was found that the -1 charge state was the most stable for a wide range of Fermi levels, and that the F atom preferred sites which were surrounded by group-III atoms. These characteristics were explained by recalling that F had the highest electronegativity. It was found that diffusion properties, such as the diffusion path and the diffusion barrier height, were similar in all of the present binary semiconductors. The estimated barrier heights were also comparable to the experimentally obtained barrier height in In0.52Al0.48As; thus suggesting that the diffusion properties in InAlAs were also similar. This implied that the experimentally observed selective F incorporation into InAlAs was not due to the diffusion properties. It was suggested that the F atom formed a F-Si defect complex in InAlAs, but it was found that a F atom in the -1 charge state had a stability which was comparable to that of a F-Si defect complex in the binary semiconductors. This implied that F-Si defect complexes and isolated F atoms in the -1 charge state coexisted in InAlAs. This coexistence was consistent with observations of the F-Si defect complex, as well as with observed F-doping effects such as donor passivation and a decrease in electron mobility.

Fluorine Atoms in AlAs, GaAs and InAs: Stable State, Diffusion and Carrier Passivation. A.Taguchi, T.Ohno, T.Sasaki: Physical Review B, 2000, 62[3], 1821-7