Effect of Bi surfactant on atomic ordering of GaAsSb

Abstract

The addition of small quantities of a Bi surfactant is shown to have dramatic effects on the microstructure of GaAsSb alloys grown by organometallic vapor phase epitaxy (OMVPE). Epilayers grown without Bi show weak atomic ordering in plan-view selective area electron diffraction measurements, with periodicity of three or six times the [110] lattice spacing as previously reported. The addition of Bi at a ratio of 1% Bi∕Ga to the gas flow results in the appearance of strong CuAu and chalcopyrite ordering, as determined from electron diffraction measurements in both undoped, and heavily carbon doped layers. High-resolution, transmission electron microscopy lattice images clearly show the coexistence of {100}, {210} ordered and disordered structures with domain sizes of ∼10–20nm. Photoluminescence shows no band gap changes in GaAsSb samples with and without {100} and {210} ordering.