Propagation of guided optical waves in thick GaN layers grown on (0001) sapphire

We report on the propagation of guided optical modes in insulating and Si-d oped n-GaN layers grown by low-pressure metalorganic chemical vapor deposit ion (MOCVD) on (0001) sapphire substrates. The effective refractive indices of the guided modes were measured using the prism-coupling technique for l ayers with thicknesses from 1 to 6 mu m. Ordinary and extraordinary refract ive indices of GaN layers at wavelength of 632.8 nm were evaluated from the comparison of the measured index values and the index values calculated by solving the characteristic equation for a planar optical waveguide. The ob tained results are in a good agreement with the step-like index profile mod el, indicating a high optical homogeneity of the investigated layers. (C) 2 000 American Institute of Physics. [S0003-6951(00)05116-0].