GaN single crystals are grown from the solution of atomic nitrogen in liquid Ga at N2 pressure up to 20 kbar. The crystals reaching dimensions of 1cm, with dislocation density of 103 - 105 cm-2 are currently obtained and successfully used for homoepitaxy by MOCVD and MBE.
The increase of the maximum size of GaN crystals with stable morphology requires the increase of the volume of the crucible. Beside the obvious geometric factors, the increase of the volume of the furnace and crucible allows to achieve much better control of supersaturation profiles in the solution and therefore better control of growth process. It helps to avoid morphological instabilities and leads to the growth of transparent, inclusion free crystals.
In the paper, the results of crystallization of substrate quality GaN crystals obtained with the use of large volume high pressure reactor will be presented. The crystals were characterized by High Resolution X-ray Diffraction and Atomic Force Microscopy. It will be shown that the quality of GaN crystals does not deteriorate with the increasing size and that epi-ready surfaces of GaN substrates can be obtained. Two-dimensional growth by propagation of monoatomic steps of GaN homoepitaxial layers will be presented as a verification of the quality of GaN substrates.