Determination of band offsets between p-NiO gate electrode and unintentionally doped GaN for normally-off GaN power device

Combining the p-NiO gate electrode and the stack barrier structure with unintentionally doped GaN insertion layer (serves as etching termination layer) is promising for achieving normally-off GaN power device. The band alignment and band offsets at the interface of NiO and GaN insertion layer play a crucial role in determining the performance of GaN device. In this letter, the p-NiO thin film/unintentionally doped GaN heterojunction was fabricated through a simple thermal oxidation method. The p-NiO thin film presents face-centered cubic crystalline structure with a band gap of approximately 3.69 eV. The interfacial band alignment of the heterojunction is characterized by X-ray photoelectron spectroscopy. Based on core-level binding energies and valence band maximum values, the valence and the conduction band offsets were determined to be 1.16 eV and 1.45 eV, respectively. The NiO/GaN heterojunction is concluded to be type-II staggered band configuration.