Contactless electroreflectance study of Fermi-level pinning at the surface of cubic GaN

Van Hoof structures C. Van Hoof, K. Deneffe, J. De Boeck, D. J. Arent, and G. Borghs, [Appl. Phys. Lett. 54, 608 (1989)] with various thicknesses of the undoped layer, for which a homogeneous built-in electric field is expected, were grown for studies of the Fermi-level pinning at the surface of cubic GaN. The built-in electric field in the undoped GaN layer was determined from contactless electroreflectance measurements of Franz–Keldysh oscillations. A good agreement between the determined and calculated electric field has been found for the Fermi-level located ∼0.4 eV below the conduction band at the surface.