Angle-resolved photoemission study and first-principles calculation of the electronic structure of GaTe

The electronic band structure of GaTe is calculated by numerical atomic orbital density-functional theory, in the local-density approximation. In addition, the valence-band dispersion along various directions of the GaTe Brillouin zone is determined experimentally by angle-resolved photoelectron spectroscopy. Along these directions, the calculated valence-band structure is in good concordance with the valence-band dispersion obtained by these measurements. It is established that GaTe is a direct-gap semiconductor with a band gap located at the Z point, that is, at a Brillouin-zone border in a direction perpendicular to the layers. The valence-band maximum shows a marked p-like behavior, with a pronounced anion contribution. The conduction band minimum arises from states with a comparable s- p-cation and p-anion orbital contributions. Spin-orbit interaction appears to especially alter the dispersion and binding energy of states of the topmost valence bands lying at Γ. Spin-orbit interaction favors a hybridization of the topmost pz-valence band with deeper and flatter pₓ-py bands, and the valence-band minimum at Γ is raised toward the Fermi level since it appears to be determined by the shifted-up pₓ-py bands.