Effect of bismuth flux on the optical and morphological properties of GaAsBi grown by Molecular Beam Epitaxy

Optical and morphological characterizations of GaAsBi bulk layer with different bismuth fluxes are reported in this work. A set of GaAsBi samples are grown by using MBE machine at fixed growth temperature and layer thickness. Bismuth cell temperature ranging between 450 to $475^{\circ} C$ are used during the growth to study the effect on bismuth content in the layer. Photoluminescence study shows different peak wavelength output indicating different bismuth percentage incorporated to GaAs during the growth. More bismuth is incorporated as the bismuth cell temperature increase. Then, it saturates after $465^{\circ}C$. However, the photoluminescence intensity is lower at device with higher bismuth content. This is due to oversupplying of bismuth, and it affects the optical behaviour and surface morphology. Nomarski imaging study provides surface tomography in term of three-dimensional image structure of the devices. Different density of metallic droplets is identified on the samples tested confirming the oversupply of bismuth during the growth process. In conclusions, these characterizations allow us to identify the bismuth fluxes needed for optimum atom incorporation without compromising the quality of the device surface.