Electronic properties of GaAsBi(001) alloys at low Bi content

We present an in-depth investigation of structural and electronic properties of GaAsBi epilayers. High (001) crystalline order is achieved using careful molecular beam epitaxy and surface preparation procedures. High surface order allows us to use x-ray, ultraviolet, and angle-resolved photoemission spectroscopy at variable photon energies and to disentangle electronic effects of an atomically thin Bi-rich surface layer with $(2\ifmmode\times\else\texttimes\fi{}3)$ symmetry from those of Bi atoms incorporated in the GaAs bulk matrix. The influence of bulk-integrated Bi concentrations on the GaAs band structure becomes visible in angle-resolved photoemission after removing Bi-rich surface layers by a brief and mild ion bombardment and subsequent annealing treatment. Experimental observations are supported by density functional theory simulations of the valence band structure of bulk and surface-reconstructed GaAs with and without Bi. Bi-induced energy shifts in the dispersion of GaAs heavy and light hole bulk bands are evident both in experiment and theory, which are relevant for modulations in the optical band gap and thus optoelectronic applications.