AlxGa1-xN is characterized by a significant spontaneous and piezoelectric polarization, which increases with the aluminum content. As a result, a surface bound charge is present, which favors compensation by surface states and influences the reliability of AlGaN/GaN devices. This work, therefore, focused on the effects of the polarization charge for GaN and AlGaN with three different aluminum concentrations 15%, 25%, and 35%. The band bending of AlxGa1-xN surfaces was measured after a N2/H2 plasma pretreatment, which reduced the carbon and oxygen contamination below the detection limit of x-ray photoelectron spectroscopy. Surface band bending was then related to surface states, where the band bending of oxygen-free surfaces - as obtained with a high-temperature, immersed hydrogen/nitrogen plasma clean - scales with the aluminum content. In addition, the band offsets at the plasma-enhanced atomic layer deposited SiO2/AlxGa1-xN interface were measured, giving 3.4 eV, 3.3 eV, 3.3 eV, and 3.0 eV for respective 0%, 15%, 25%, and 35% aluminum concentrations. These values are in accordance with the charge neutrality level model, which implies that SiO2 will confine carriers over nearly the full range of the aluminum content.
ASJC Scopus subject areas
- Physics and Astronomy(all)