The electronic structure of the epitaxial GaN/Si(111) layers and the Li/GaN/Si(111) interface with a monolayer Li coverages has been studied in situ under ultrahigh vacuum conditions. The experiments were carried out using photoelectron spectroscopy with synchrotron radiation in the photon energy range 75 eV – 850 eV. The photoemission spectra in the valence band and the core levels of Ga 3d, N 1s, and Li 1s are studied for the monolayer Li coating. It is found that Li adsorption causes a significant decrease in the intensity of the photoemission line of the intrinsic surface state and the appearance of an induced surface state due to charge transfer between the adsorbed Li layer and surface Ga atoms. It has been found that the GaN/Si(111) surface has predominantly Ga polarity. The Li/GaN/Si(111) interface has a semiconductor character.

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