Photoemission study of HfO${}_2$ films deposited on GaN/Al${}_2$O${}_3$

Heterostructure composed of HfO${}_2$ and GaN has attracted much attention due to its outstanding potential for electronics. The band alignment at their interface is crucial for understanding the electrical properties. Here, X-ray photoelectron spectroscopy, through measuring the binding energy difference between core level and valence band maximum, was used to determine the band alignment at the interface between HfO${}_2$ and GaN. The type I or "straddling" band alignment with valence and conduction band offsets of 1.03 eV and 1.77 eV, respectively, was realized in HfO${}_2$/GaN heterostructure.