Scanning probe investigation of surface charge and surface potential of GaN-based heterostructures

Scanning Kelvin probe microscopy (SKPM) and electrostatic force microscopy (EFM) have been employed to measure the surface potentials and the surface charge densities of the Ga- and the N-face of a GaN lateral polarity heterostructure (LPH). The surface was subjected to an HCl surface treatment to address the role of adsorbed charge on polarization screening. It has been found that while the Ga-face surface appears to be unaffected by the surface treatment, the N-face surface exhibited an increase in adsorbed screening charge density (1.6 +/- 0.5x10(10) cm(-2)), and a reduction of 0.3 +/- 0.1 V in the surface potential difference between the N- and Ga-face surfaces.