Indium nitride: Evidence of electron accumulation

The electronic properties of clean InN(0001) surfaces have been investigated by high-resolution electron-energy-loss spectroscopy of the conduction band electron plasmon excitations and valence band x-ray photoemission spectroscopy. An intrinsic surface electron accumulation layer is found to exist, with the associated downward band bending occurring to neutralize charged donor-type surface states. Semiclassical dielectric theory simulations of the energy-loss spectra and charge profile calculations indicate a surface state density of 2.5(±0.2)×1013 cm−2 and a surface Fermi level of 1.64±0.10 eV above the valence band maximum and 0.89±0.10 eV above the conduction band minimum. This location of the surface Fermi level is in agreement with the valence band photoemission spectra. These observations are compared with recent evidence of electron accumulation at InN surfaces provided by capacitance–voltage profiling, Hall measurements, and synchrotron-radiation photoemission spectroscopy.