The characteristics of clean n-and p-type GaN (0001) surfaces and the interface between this surface and Si0 2 , Si 3 N 4 , and Hf0 2 have been investigated. Layers of Si0 2 , Si 3 N 4 , or Hf0 2 were carefully deposited to limit the reaction between the film and clean GaN surfaces. After stepwise deposition, the electronic states were measured with x-ray photoelectron spectroscopy (XPS) and ultraviolet photoemission spectroscopy (UPS). A valence band offset (VBO) of 2.0 ± 0.2 eV with a conduction band offset (CBO) of 3.6 ± 0.2 eV was determined for the GaN/Si0 2 interface. The large band offsets suggest Si0 2 is an excellent candidate for passivation of GaN. For the GaN/Si 3 N 4 interface, type II band alignment was observed with a VBO of -0.5 ± 0.2 eV and a CBO of 2.4 ± 0.2 eV. While Si 3 N 4 should passivate n-type GaN surfaces, it may not be appropriate for p-type GaN surfaces. A VBO of 0.3 ± 0.2 eV with a CBO of 2.1 ± 0.2 eV was determined for the annealed GaN/Hf0 2 interface. An instability was observed in the Hf0 2 film, with energy bands shifting -0.4 eV during a 650 °C densification anneal. The electron affinity measurements via UPS were 3.0, 1.1, 1.8, and 2.9 ±0.1 eV for GaN, Si0 2 , Si 3 N 4 , and Hf0 2 surfaces, respectively. The deduced band alignments were compared to the predictions of the electron affinity model and deviations were attributed to a change of the interface dipole. Interface dipoles contributed 1.6, 1.1 and 2.0 ± 0.2 eV to the band alignment of the GaN/Si0 2 , GaN/Si 3 N 4 , and GaN/Hf0 2 interfaces, respectively. It was noted that the existence of Ga-0 bonding at the heterojunction could significantly affect the interface dipole, and consequently the band alignment in relation to the GaN.