Kinetically limited growth of GaAsBi by molecular-beam epitaxy

The growth of GaAsBi alloys is plagued by the appearance of Bi droplets due to excess Bi that accumulates during growth. Here we present an alternate growth regime that kinetically limits the amount of Bi on the surface, eliminating Bi droplets for a wide range of Bi compositions, while yielding atomically smooth surfaces. Growth rate plays a major role in the amount of Bi that accumulates on the surface, with high growth rates and low Bi fluxes leading to less surface Bi. A balance can be achieved between low Bi coverage, the resultant rough surfaces, and the excessive Bi coverage that leads to Bi droplets. Bi incorporation in this growth regime is linear with Bi flux and scales inversely with growth rate. Unlike previous studies, there is no sign of saturating Bi incorporation with increasing Bi flux, allowing for intuitive prediction and control of Bi content in this regime.

► GaAsBi growth by molecular-beam epitaxy.
► Bi segregation is kinetically limited at higher growth rates.
► Atomically smooth, droplet-free GaAsBi is demonstrated.
► Smooth growth requires selecting the proper growth rate for a given Bi composition.