The roles of Bi in InAs and InAsBi nanostructure growth

Incorporation of bismuth into the III-V semiconductors expands the bandgap towards the mid-infrared range by bandgap bowing and spin-orbit splitting, providing new opportunities and functionalities in optoelectronic applications. However, growing high Bi-containing III-V-Bi alloys remains a challenge due to the large atomic radius difference and miscibility gap between III-Vs and Bi. Here, we report a detailed study on incorporation of Bi into InAs grown by molecular beam epitaxy. Under low and intermittent Bi supply, Bi predominantly functions as a surfactant, guiding phase transitions in InAs nanowires from wurtzite to zinc blende. Conversely, high and continuous Bi supply increases Bi concentration in the InAsBi alloy, prompting the development of 3D dendritic and 1D axial heterostructures. This elevated Bi incorporation is likely due to the formation of Bi droplets, which shifted the growth into Bi-catalyzed growth. Density functional theory calculations confirm the bandgap of the 12.5% Bi-incorporated InAsBi alloy at 0.038 eV, underscoring its prospective applications in the mid and long-wave infrared spectrum.