Epitaxial lateral overgrown GaN on SiC was studied. A defect density of below 2.2 x 107/cm2 in the wings, compared to 2 x 109/cm2 in the windows, was achieved. Interaction of the overgrown GaN with the SiO2 mask caused a few degrees of wing-tilt, and a transition region of high defect-density between windows and wings. Diminished photoluminescence, strong tensile stresses and a defect-correlated line (at around 3.4eV) emerged in this up-to-2μ-wide transition region. By changing the mask material from SiO2 to SiN, it was possible to reduce the wing-tilt markedly, to below 0.7°. This eliminated the defective transition region and extended the low strain and the low defect density area of the epitaxial lateral overgrown wings. Microphotoluminescence, transmission electron microscopy, X–ray diffraction and scanning electron microscopy were used to study strain, wing-tilt and threading dislocations in the epitaxial lateral overgrown samples. Use of the first moment of the microphotoluminescence spectra was also demonstrated to be an effective means for measuring strain distributions.

Correlation of Strain, Wing Tilt, Dislocation Density and Photoluminescence in Epitaxial Lateral Overgrown GaN on SiC Substrates. N.Gmeinwieser, K.Engl, P.Gottfriedsen, U.T.Schwarz, J.Zweck, W.Wegscheider, S.Miller, H.J.Lugauer, A.Leber, A.Weimar, A.Lell, V.Härle: Journal of Applied Physics, 2004, 96[7], 3666-72