Is electron accumulation universal at InN polar surfaces?

Recent experiments indicate the universality of electron accumulation and downward surface band bending at as-grown InN surfaces with polar or nonpolar orientations. Here, we demonstrate the possibility to prepare flatband InN $(0001¯)$ surfaces. We have also measured the surface stoichiometry of InN surfaces by using core-level photoelectron spectroscopy. The flatband InN $(0001¯)$ surface is stoichiometric and free of In adlayer. It implies that the removal of In adlayer at the InN $(0001¯)$ surface leads to the absence of downward surface band bending. On the other hand, the stoichiometric InN (0001) surface still exhibits surface band bending due to the noncentrosymmetry in the wurtzite structure.