Investigation of Surface Band Bending of Ga-Face GaN by Angle-Resolved X-ray Photoelectron Spectroscopy

The surface band bending of Ga-face n-type GaN is clarified via angle-resolved X-ray photoelectron spectroscopy (ARXPS) of test samples with and without hydrofluoric acid (HF) cleaning. For samples without HF cleaning, a slight downward band bending is obtained, indicating an accumulated GaN surface. On the other hand, a 0.3-eV upward band bending is observed on samples with HF cleaning, pointing to a depleted surface region. The change may be ascribed to the removal of the native gallium oxide (and the associated positive surface charges) by the HF etchant, thus resulting in the n-type GaN being depleted by the polarization-induced negative surface charges (previously compensated). Based on the ARXPS results and an electrostatics analysis, a net positive surface charge density of 2.09 x 10(12) cm(-2) is obtained for samples without HF cleaning, whereas a net negative surface charge density of 1.0 x 10(12) cm(-2) is obtained for samples with HF cleaning. (C) 2016 The Electrochemical Society. All rights reserved.