The GaN/substrate bi layer is cooled from a growth temperature at which {HEAD ~ the bulk layer} is grown to {TAIL ~ an ambient temperature}, wherein GaN material of the bi layer cracks laterally and separates from the substrate to form a substantially crack free free standing GaN article 
is grown to
The GaN / substrate bi layer is cooled from a growth temperature at which { HEAD ~ the bulk layer } is grown to { TAIL ~ an ambient temperature } , wherein GaN material of the bi layer cracks laterally and separates from the substrate to form a substantially crack free free standing GaN article
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH