Carrier concentration and surface electron accumulation in indium nitride layers grown by high pressure chemical vapor deposition

Electronic and structural properties of InN layer grown by high pressure chemical vapor deposition have been studied by high-resolution electron energy loss spectroscopy (HREELS) and room temperature infrared reflection measurements. HREEL spectra after atomic hydrogen cleaning exhibit N–H bending and stretching vibrations with no indications of an indium overlayer or droplet formation. Broad conduction band plasmon excitations are observed centered at 3100–4200 cm^-1 at various locations across the surface in HREEL spectra acquired with 25 eV incident electron energy. The plasmon excitations are shifted about 300 cm^-1 higher in spectra acquired using 7 eV electrons due to higher plasma frequency and carrier concentration at the surface than in the bulk which indicates surface electron accumulation. Infrared reflectance data acquired at various spots across the surface showed a similar variation in bulk plasma frequency. A three phase thin film reflection model fitted to the infrared data yielded carrier concentrations from 8.2×10¹⁹ to 1.5×10²⁰ cm^-3 and carrier mobilities from 105 to 210 cm²/V s.