Poole-Frenkel emission in epitaxial nickel oxide on AlGaN/GaN heterostructures

In this letter, the conduction mechanism through epitaxial nickel oxide (NiO) dielectric films grown by metal-organic chemical vapor deposition on AlGaN/GaN heterostructures was investigated. In particular, macroscopic 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 microscopic measurements were carried out to directly image the presence of preferential current spots on the NiO surface, which have been correlated to the defects responsible for the PF emission.