Mechanisms of lateral epitaxial overgrowth of gallium nitride by metalorganic chemical vapor deposition

We investigate the effect of growth temperature (1015-1100 degrees C), growth duration (3-90 min), and pattern geometry on the lateral epitaxial overgrowth (LEO) of GaN stripes using a SiO2-masked GaN/Al2O3 seed. The mask openings (5 and 10 mu m) are aligned in the < 1 (1) over bar 0 0 > directions and the fill factor (ratio of opening width to pattern period) is varied between 0.01 and 0.5. Vertical {1 1 (2) over bar 0} sidewalls are observed in conditions of hgh temperature or high fill factor, whereas inclined {1 1 (2) over bar n} facets (n approximate to 1-2.5) are observed in conditions of low temperature or low fill factor. The set of exposed facets is roughly independent of growth duration between 3 and 90 min, We suggest that the observed morphologies result from the bonding structure of the various facets in conjunction with the local variations of the V/III ratio. (C) 1998 Elsevier Science B.V. All rights reserved.