Valence band discontinuity at the GaN/SiC(0001) heterojunction studied in situ by synchrotron-radiation photoelectron spectroscopy

The valence band discontinuity and the interface formation of the n-type hexagonal GaN/SiC(0 0 0 1) heterointerface have been studied by means of angle-resolved photoelectron spectroscopy using synchrotron radiation. Gallium nitride thin films were grown on SiC(0 0 0 1) substrates by molecular beam epitaxy using either nitrogen plasma or ammonia gas as nitrogen source. The interface properties were investigated in situ by a combination of core level and valence band spectroscopy. The interface formation and the valence band offset of the epitaxial GaN films grown by the two methods have been compared. The GaN/SiC interface shows Si-N bond formation and the measured valence band discontinuity is 1.02 +/- 0.1 eV for the ammonia grown films and 1.10 +/- 0.1 eV for the nitrogen plasma grown films. These values are in good agreement with the theoretical prediction and indicate that the band alignment of the GaN/SiC heterojunction is of the staggered type. (c) 2005 Elsevier B.V. All rights reserved.