Investigation of hydride vapor phase epitaxial growth of AlN on sputtered AlN buffer layers

The influence of sputtered AlN buffer annealing conditions on the crystal quality of AlN thick films, fabricated by hydride vapor phase epitaxy, has been investigated. Compared with the AlN thick film grown on a sputtered AlN buffer layer without annealing, AlN thick films on annealed sputtered AlN buffers exhibit narrower XRC peaks and fewer cracks. In this work, the crystalline quality of AlN thick films without cracks can be most improved by using sputtered AlN buffer layers annealed at 1500 degrees C for 2 h, with FWHM values of the (0002)- and (1012)-plane of 28 and 410 arcsec, respectively. This improvement in the crystal quality of the AlN films can be attributed to the reduction of dislocations, which are firstly caused by grain growth of the buffer layer during annealing, followed by dislocation bending and interaction during the regrowth process. Furthermore, the crack suppression of AlN thick films on annealed sputtered AlN buffers is likely due to the strain relaxation related to the generation of nano-voids at the AlN and sapphire interface.