Photoemission Studies of the Electronic Structure of GaN Grown by Plasma Assisted Molecular Beam Epitaxy

The results of experimental studies of the electronic and photoemission properties of the GaN epitaxial layer grown by molecular beam epitaxy with plasma activation of nitrogen on a SiC/Si (111) substrate are presented. The electronic structure of the GaN surface and the ultrathin Li/GaN interface was first studied in situ under ultrahigh vacuum with various Li coatings. The experiments were carried out using photoelectron spectroscopy with synchrotron radiation in the photon energy range of 75–850 eV. Photoemission spectra in the region of the valence band and surface states and photoemission spectra from N 1s, Ga 3d, and Li 2s core levels are studied with various submonolayer Li coatings. It is found that Li adsorption causes significant changes in the general form of the spectra caused by charge transfer between the Li layer and the lower N and Ga layers. It is established that the GaN surface has predominantly the N polarity. The semiconductor nature of the Li/GaN interface is shown.