Electron accumulation at nonpolar and semipolar surfaces of wurtzite InN from generalized infrared ellipsometry

The free electron properties of nonpolar (112¯0)-oriented and semipolar (101¯1)-oriented wurtzite InN films are studied by generalized infrared ellipsometry (GIRSE). We demonstrate the sensitivity of GIRSE to the surface charge accumulation layer and find a distinct surface electron accumulation to occur at all surfaces. The obtained surface electron sheet densities are found to vary from 0.9×1013 to 2.3×1014 cm−2 depending on the surface orientation and bulk electron concentration. The upper limits of the surface electron mobility parameters of 417–644 cm2/V s are determined and discussed in the light of electron confinement at the surface.