Influence of buffer layers on metalorganic vapor phase epitaxy grown GaN on Si(001)

GaN layers grown by metalorganic vapor phase epitaxy on Si(001) substrates were investigated by x-ray analysis and scanning electron microscopy. Several sample series were grown changing the AlN/GaN buffer layer deposition temperature, sequence, and thickness. By variation of the buffer layer structure, two different growth orientations could be realized. First, GaN grows $c$ -axis oriented on the Si(001) substrates with two rotational alignments. Second, the $r$ plane $\text{(101̄2)}$ of the hexagonal GaN-structure is oriented parallel to the surface. In the latter case, four rotational in-plane alignments are observed. By a miscut (2°–6° off) of the Si substrates one of these alignments is preferred.