Conduction mechanisms in epitaxial NiO gate dielectric on AlGaN/GaN heterostructure

The electron transport through epitaxial nickel oxide (NiO) films grown by metal-organic chemical vapor deposition (MOCVD) on AlGaN/GaN heterostructures was investigated. Current-voltage measurements carried out at different temperatures allowed to demonstrate that Poole-Frenkel (PF) mechanism rules the conduction through the dielectric layer, with an emission barrier of 0.2 eV. Conductive Atomic Force Microscopy measurements faced the presence of preferential current spots on the NiO surface, which have been correlated to the defects responsible for the PF emission. The interface state density has been also determined.