Bismuth surface segregation and disorder analysis of quaternary (Ga,In)(As,Bi)/InP alloys

The incorporation of small fractions of bismuth atoms in III–V semiconductors such as (Ga,In)As leads to a vast decrease of the bandgap energies accompanied by an increase of the spin-orbit splitting energies of the alloy compared to the host material. This effect is commonly described by an anticrossing of the bismuth-level with the valence bands of the matrix. Growth and characterization of quaternary alloys like (Ga,In)(As,Bi) remains challenging due to the required low growth temperatures, since Bi generally tends to have pronounced surfactant properties on the one hand and the similar influence in Bi and In on most structural, electronic, and optical properties such as the lattice constant or the bandgap energy. In this study, we uniquely identify surface diffusion of the bismuth atoms with X-ray photoelectron spectroscopy and relate the finding to growth parameters and photoluminescence properties and X-ray diffraction patterns of the material. We show the influence of different partial pressures of the MOVPE growth on the bismuth segregation process as well as a consequence thereof the disorder properties of those samples compared to (Ga,In)As/InP reference alloys.