Investigation of electromechanical distortions in gallium nitride by reflectance anisotropy spectroscopy

Real time reflectance spectroscopy has been used to investigate the extent and development of dielectric anisotropy during chemical beam epitaxy of ga llium nitride on a GaAs(001) substrate using a low temperature aluminium ni tride buffer layer. Reflection anisotropy between the [(1) over bar 10] and [110] directions indicates a strong cubic symmetry with bulk anisotropic s trains of the order of 0.001. post-growth reflectance measurements have bee n made to investigate electromechanical distortions in the gallium nitride epilayer when an electric field was applied in the [001] direction, The d(1 4) piezoelectric modulus of cubic gallium nitride is estimated to be 1.95 p m V-1. Reflectance anisotropy spectroscopy is shown to be a sensitive metho d for the measurement of electromechanical effects in thin films, and in pa rticular a novel method for investigating thin film semiconductor piezoelec tric materials. (C) 2000 Elsevier Science S.A. All rights reserved.