Surface morphology and Bi incorporation in GaSbBi(As)/GaSb films

•X-ray diffraction and Rutherford backscatter analysis show residual As in GaSbBi.•Droplets form that show sub-droplets, phase separation, and etching.•Bi and residual As incorporation results in film strain auto-compensation.

Several GaSbBi(As)/GaSb films were grown to investigate the effects of Bi on GaSb surface morphology and bulk composition as a function of growth conditions. Scanning electron microscopy of the surface shows several biphasic droplets consisting of Ga- and Bi-rich phases ≈1μm in diameter form on the surface. Some of these droplets exhibit more unusual features such as facets, sub-droplets, and droplet etching into the underlying film. Bi droplet coverage shows a direct increase with increasing Bi:Ga and Bi:Sb BEP ratios. Rutherford backscatter and X-ray diffraction analyses of these films show Bi concentration of up to 12% and a concurrently increasing unintentional As concentration of up to 9.3%, suggesting the presence of a strain auto-compensation mechanism during film growth. Once Bi concentration reaches 10–12%, Bi incorporation saturates, with excess Bi atoms instead accumulating in the droplets.