Structural and Optical Properties of InAsSbBi Grown by Molecular Beam Epitaxy on Offcut GaSb Substrates

Three InAsSbBi samples are grown by molecular beam epitaxy at 400 degrees C on GaSb substrates with three different offcuts: (100) on-axis, (100) offcut 1 degrees toward [011], and (100) offcut 4 degrees toward [011]. The samples are investigated using X-ray diffraction, Nomarski optical microscopy, atomic force microscopy, transmission electron microscopy, and photoluminescence spectroscopy. The InAsSbBi layers are 210 nm thick, coherently strained, and show no observable defects. The substrate offcut is not observed to influence the structural and interface quality of the samples. Each sample exhibits small lateral variations in the Bi mole fraction, with the largest variation observed in the on-axis growth. Bismuth rich surface droplet features are observed on all samples. The surface droplets are isotropic on the on-axis sample and elongated along the [01 (1) over bar] step edges on the 1 degrees and 4 degrees offcut samples. No significant change in optical quality with offcut angle is observed.