Effect of grain boundary scattering on electron mobility of n-polarity InN films

Transport properties of InN layers with both lattice polarities are reported. It is proposed that grain boundaries form potential barriers for electrons and thus lead to a reduction of electron mobility. However, these grain boundaries are important scattering centers only in the N-polarity InN films, but not in the In-polarity ones, which is consistent with the grain feature of the N-polarity InN surfaces. The carrier mobility in grain boundaries is estimated to be about 75 cm² V^-1 s^-1 at room temperature for our sample, far less than the carrier mobility in the grains.