Experimental Determination of Electron Affinities for InN and GaN Polar Surfaces

Abstract

We have measured the electron affinities of clean, stoichiometric InN and GaN polar surfaces via ultraviolet photoelectron spectroscopy. The electron affinities of InN were measured to be 4.7 and 4.6 eV for In- and N-polar surfaces, respectively. In contrast, the electron affinities of GaN vary greatly with the film polarity, i.e., 3.8 and 3.3 eV for Ga- and N-polar surfaces, respectively. We propose that the difference between polar surfaces originates from the spontaneous polarization effect. Furthermore, it's closely related to the film carrier concentration. With the measured electron affinities, we are able to confirm the known polar heterojunction band alignments.