Abstract:This paper introduces a photo-assisted atomic force microscope (AFM) local oxidation technique which is capable of producing highly smooth oxide patterns with heights reaching several tens of nanometres on both n- and p-types of GaN (and in principle on most semiconductors) without the use of chemicals. The novel methodology relies on UV illumination of the surface of the substrate during conventional AFM local oxidation. A low 1.2 V threshold voltage for n-type GaN was obtained, which can be explained by UV photo-generation of excess electron–hole pairs in the substrate near the junction, thereby reducing the electric field required to drive carrier flow through the tip–sample Schottky barrier. It was demonstrated that the presence or absence of light alone was sufficient to switch the growth of the oxide on or off. The photo-assisted AFM oxidation technique is of immediate interest to the semiconductor industry for the fabrication of GaN-based complementary metal–oxide–semiconductor devices and nanodevices, improves chances for AFM-type data storage, and presents new degrees of freedom for process control technique.