PUB - Publikationen an der Universität Bielefeld

We have studied the symmetry properties of the bands of the layered semiconductor GaSe along the Delta direction by means of spin-resolved electron spectroscopy using circularly polarized synchrotron radiation and by means of a relativistic LAPW band-structure calculation. The photoelectron spectra show in the main a pair of weakly dispersing peaks caused by direct transitions from valence-band states with symmetries Delta(9)(5), Delta(9)(6) and Delta(7)(5), Delta(8)(6). Our data determine the spin-orbit splitting of these valence bands to be DeltaE(so)=0.3+/-0.1 eV. We find a gap in the unoccupied bands along Delta about 8 eV above the fundamental gap. The analysis of the photoelectron spin polarization reveals that also unoccupied states with low symmetries Delta(7)(5), Delta(8)(6) and Delta(9)(5), Delta(9)(6) are involved in excitation and emission. Spin resolved spectra measured at Auger electrons following the decay of Ga 3d core holes confirm that p derived unoccupied states exists below the vacuum level.