Microstructure of ordered nanodomains induced by Bi surfactant in OMVPE-grown GaAsSb

Bismuth surfactant is shown to have dramatic effects on the microstructure of GaAsSb alloys grown on nominally [0 0 1] InP substrates by organometallic vapor phase epitaxy. The addition of Bi at a ratio of 1% Bi/Ga in the gas flow results in the formation of CuAu {1 0 0} and chalcopyrite {2 1 0} ordered and disordered structures. Domains are approximately 10-20 nm in diameter for both undoped and heavily carbon-doped GaAsSb layers, and they account for ∼40% (CuAu) and ∼3% (chalcopyrite) of the total surface area. The addition of this small amount of Bi does not affect growth rate, Sb concentration, or surface morphology. Ordered domains with c-axes along the [0 0 1] growth direction were not observed. Photoluminescence and optical absorption measurements did not detect band gap changes in GaAsSb samples with and without {1 0 0} and {2 1 0} ordering, respectively.