Growth of GaN directly on Si(111) substrate by controlling atomic configuration of Si surface by metalorganic vapor phase epitaxy

The direct growth of a GaN epitaxial layer on a Si(111) substrate by metalorganic vapor phase epitaxy (MOVPE) was performed using a low-temperature (LT)-GaN buffer layer with no Al-containing intermediate layer (e.g., A1N or AlGaN). No deterioration in the Si surface caused by the reaction between Si and Ga vapor was observed. However, when there were Ga droplets on the surface, Ga and Si formed a Ga-Si alloy, which caused the generation of numerous holes on the surface by melt-back etching at high temperatures. In addition, it was revealed that the coverage of the LT-GaN buffer layer on Si was strongly affected by the hydrogen (H₂) partial pressure in the carrier gas. Using nitrogen (N₂) carrier gas, a complete coverage of the LT-GaN buffer layer could be achieved directly over the Si surface. These features can be explained by the facts that the Si surface is partially terminated by hydrogen atoms and the coverage of hydrogen on Si surface depends on H ₂ partial pressure.