Epitaxial lateral overgrowth of GaN on silicon (111)

摘要

Epitaxial lateral overgrowth (FLOG) of GaN was achieved on silicon (111) by metalorganic vapor phase epitaxy. Lateral expansion is obtained at high growth temperature (1120°C), low pressure (100 mbar) and with high V/Ill ratio (8000). Growth rate of the (0001) c-plane and the lateral facets was investigated for stripes along the [1010]{sub}GaN and the [1120]{sub}GaN crystallographic directions. Although full coalescence is more difficult on Si (111) substrate than on sapphire, FLOG process with large mask is possible with stripes oriented along the [1010]{sub}GaN axis. Coalescence can be achieved with a 10 μm period mask with an overgrown layer thickness lower than 3 μm. Atomic force microscopy and transmission electron microscopy are used to characterize the quality of the layers. The density of dislocations can be decreased from 8×10{sup}8 cm{sup}(-2) in the underlying layer of GaN down to 5×10{sup}7 cm{sup}(-2) in the laterally overgrown region, and 8 ×10{sup}8 cm{sup}(-2) in the opening of the mask. Cathodoluminescence was used to determine the stress in the FLOG layer before and after coalescence.