Improved GaN layer morphology by hydride vapor phase epitaxy on misoriented Al(2)O(3) wafers

Crack-free thick GaN layers have been grown by hydride vapor phase epitaxy on on-axis as well as on off-axis GaN-Al2O3 templates. A dramatic difference in surface quality could be traced back to the misorientation of the substrates: Mirror-like layers have been obtained for slightly off-oriented substrates, whereas pyramids and other surface structures were found on samples grown on exactly oriented wafers. Such excellent surfaces may make further surface treatment prior to a subsequent use of these wafers in further epitaxial processes obsolete.