Temperature invariance of InN electron accumulation

The temperature dependence of the electron accumulation at clean InN(0001)-(1x1) surfaces has been investigated by high-resolution electron-energy-loss spectroscopy. Semiclassical dielectric theory simulations of the energy-loss spectra at 295 K and 565 K along with solutions to the Poisson equation enable carrier profiles of the near-surface region to be determined. These measurements reveal similar electron accumulation for both temperatures. The surface-state density, N-ss, and the surface Fermi level, E-FS, were found to be independent of temperature, with N(ss)similar to2.4x10(13) cm(-2) and E(FS)similar to1.5 eV above the valence-band maximum. The slight difference in the carrier profiles between the two temperatures can be accounted for by the change in the electron screening length. This is a consequence of the reduction in the band gap that results in a decrease in the electron effective mass with increasing temperature.