Electroreflectance and band structure of gallium selenide

The electroreflectance spectrum of the layer compound gallium selenide shows that the peaks at 3.63 eV and 4.9 eV of the absolute reflectivity are due to threedimensional saddle points. The first transition is resolved in a doublet arising from a spin-orbit split valence state associated with the p orbitals of Se; this contrasts with some theoretical models and favours the view that the p x p y states of selenium are important in forming the upper valence band.