Energy dependence of electron inelastic mean free paths in bulk GaN crystals

Recent advances in fabrication and commercialization of high-brightness blue and green light-emitting devices based on gallium nitride have renewed intense research of its basic properties. Since information on electron transport processes in GaN is scarce, their systematic studies are highly desirable. The electron inelastic mean free path (IMFP) is a crucial parameter for quantitative interpretation of surface electron spectra. The energy dependence of IMFP for bulk GaN crystals with different surface concentrations of their constituents was obtained from elastic peak electron spectroscopy (EPES) with use of the Ni standard in the energy range 200–2000 eV. The measured IMFPs were compared with the values predicted by the TPP-2M and G-1 formulae. A reasonable agreement was found between the measured IMFPs in bulk GaN with an ideal stoichiometric surface composition and the corresponding calculated IMFPs. Compared with the bulk IMFPs, experimental IMFPs valid for the GaN sample with a thin surface layer enriched in ∼70 at.% Ga are only slightly smaller by 5–10%, depending on the electron energy.