Electronic structure of wurtzite- and zinc blende-GaN studied by angle-resolved photoemission

Abstract

The valence band structures of both wurtzite- and zinc blende-GaN were investigated by angle-resolved photoemission spectroscopy. It was found the k dispersions of the upper valence bands show band structures corresponding to wurtzite or zinc blende structure. In wurtzite-GaN, band width of the upper valence band is 6.7 eV in good agreement with the theoretically predicted value. However, the binding energy of Ga 3d level was found to be 15.7 eV relative to the valence band maximum, which is about 2 eV higher binding energy than those predicted by local density approximation calculations. In zinc blende-GaN, some discrepancies in the binding energy of the topmost bands around the valence band maximum was observed. We discuss the cause of these discrepancies by taking into account the strain effect.