Band offset measurements of the GaN (0001)/HfO2 interface

Photoemission spectroscopy has been used to observe the interface electronic states as ${\mathrm{HfO}}_2$ was deposited on clean n-type Ga-face GaN (0001) surfaces. The ${\mathrm{HfO}}_2$ was formed by repeated deposition of several monolayers of Hf followed by remote plasma oxidation at 300 °C, and a 650 °C densification anneal. The 650 °C anneal resulted in a 0.6 and 0.4 eV change in band bending and valence band offset, respectively. The final annealed ${\mathrm{GaN/HfO}}_2$ interface exhibited a valence band offset of 0.3 eV and a conduction band offset of 2.1 eV. A 2.0 eV deviation was found from the electron affinity band offset model.