Surface states and carrier transport properties at semipolar (11-22) n-type GaN planes

The surface states and carrier transport properties at semipolar (11-22) n-type GaN surfaces were investigated using Schottky diodes fabricated with various metals including Cu, Pd, and Pt. Thermionic field emission theory applied to the forward current-voltage curves yielded the relatively low S-parameter of 0.26, resulting in a density of surface states as high as 3.2 × 10¹³ states/cm²/eV and a large bare surface barrier height of 1.57 eV, which are associated with pinning of the Fermi level at the semipolar n-GaN surfaces.