Influences of ALD Al₂O₃ on the surface band-bending of c-plane, Ga-face GaN

The recently demonstrated approach of grafting n-type GaN with p-type Si or GaAs, by employing ultrathin Al₂O₃ at the interface, has shown the feasibility to overcome the poor p-type doping challenge of GaN. However, the surface band-bending of GaN that could be influenced by the Al₂O₃ has been unknown. In this work, the band-bending of c-plane, Ga-face GaN with ultrathin Al₂O₃ deposition at the surface of GaN was studied using X-ray photoelectron spectroscopy. The study shows that the Al₂O₃ can help suppress the upward band-bending of the c-plane, Ga-face GaN with a monotonic reduction trend from 0.48 eV down to 0.12 eV as the number of Al₂O₃ deposition cycles increases from 0 to 20. The study further shows that the band-bending can be mostly recovered after removing the Al₂O₃ layer, concurring that the introduction of ultrathin Al₂O₃ is the main reason for the surface band-bending modulation. (author)