Band alignment and Schottky behaviour of InN/GaN heterostructure grown by low-temperature low-energy nitrogen ion bombardment

Abstract

InN/GaN heterostructure based Schottky diodes are fabricated by reactive Low Energy Nitrogen Ion (LENI) bombardment at low substrate temperature (300 °C). The valence band offset (VBO) of the nitrogen ion induced In-polar InN/GaN hetero-interface has been analyzed by X-ray photoelectron spectroscopy and it is determined to be 0.72 ± 0.28 eV, a type-I straddled band alignment is formed at the InN/GaN interface. Fermi level pinning is observed to be 1.3 ± 0.1 eV above the conduction band minimum resulting in a strong downward band bending. Valence band maxima of InN/GaN show that the surface electron accumulation occurs due to the presence of In adlayer on the film. Atomic force microscopy analysis divulged the formation of a step like InN structure on the GaN surface. I–V characteristic showed that the junction between InN and GaN exhibits a Schottky type behaviour. The room temperature barrier height and the ideality factor of the InN/GaN Schottky diodes are calculated by using the thermionic emission (TE) model and found to be 0.72 eV and 20.8 respectively.