Photoreflectance (PR) modulation spectroscopy was performed to investigate surface properties of GaN films grown on sapphire substrates. From the period of the Franz-Keldysh oscillations, the surface electric field across the GaN space charge region was found to be (197.3 '' 11.4) kV/cm, which corresponds to a surface state density of 1.0 x 10e12 cm^-2. A surface barrier height (SBH) of 0.71 eV was determined by fitting the dependence of the PR intensities on pump beam power density. We suggest that a deep level is formed at 2.68 eV above the GaN valence band edge due to the large density of surface states.
Proceedings Title: MRS Electronic Proceedings
Conference Dates: November 29-December 3, 2004
Conference Location: Boston, MA
Pub Type: Conferences
GaN, Photoreflectance, Surface electronic properties