A Two-Step Method for Epitaxial Lateral Overgrowth of GaN

We report on a two-step process for the epitaxial lateral overgrowth of GaN. In the first step, the selective area epitaxy proceeds at low temperature and GaN stripes with a triangular cross section are rapidly obtained. Then, in a second step, these stripes are used as seeds for epitaxial lateral overgrowth, the growth conditions being changed either by increasing the growth temperature or by introducing a Mg precursor. Fully coalesced and planar GaN samples are thereby achieved. A comparison between samples grown without and with this two-step process evidences an additional reduction in the threading defects density with the two-step process. The dislocations emerging from the seeds are drastically reduced to 5 × 106 to 107 cm—2 between the coalescence boundaries.