Epitaxial lateral overgrowth of GaN on Si (111)

Completely coalesced epitaxial lateral overgrowth (ELO) of GaN on silicon (111) is presented for ELO layer thicknesses below 3 μm. Fast lateral expansion of the ELO-GaN was achieved by metalorganic vapor phase epitaxy at high growth temperature (1120 °C), low pressure (100 mbar), and a high V/III ratio of 8000. Thus full coalescence and a smooth surface (roughness of 5 nm across 100 μm2) are accomplished for wide SixNy masks along 〈11_00〉GaN with a 10 μm period and 3 μm openings. Atomic force microscopy and transmission electron microscopy are used to assess the quality of the layers. The density of dislocations is reduced from 8×109 cm−2 in the GaN template down to 8×108 cm−2 above the mask openings, and finally to 5×107 cm−2 in the laterally overgrown regions. The corresponding strong improvement of the optical properties and the stress present within the epilayer are evidenced by scanning cathodoluminescence microscopy.