Sublimation Growth of Bulk AlN Crystals on SiC Seeds

Abstract

AlN bulk crystals were grown by the sublimation “sandwich method” on the SiC substrates. Two types of containers were used: (i) Ta container with a surface layer of TaC created by the special annealing in contact with carbon, (ii) TaC container created by pressing of TaC powder. Cryptocrystalline AlN wafers grown by oversublimation of the original industrial high purity AlN powder were used as a vapor source. So a considerable decrease of oxygen concentration in the source (10 – 30 times) was achieved. 4H and 6H SiC bulk crystals grown by Nitride Crystals, Ltd., which were used as wafers, were crack-free, micropipe-free and have a low dislocation density (1- 4.103cm-2). The method allowed to grow thick AlN bulk crystals up to 5mm height and up to two inches in diameter with smooth mirror-like surface. X-ray diffractometry and topography of the grown AlN layers show that FWHMs of the rocking curves in ω-scan lie in the range of 60-120 arcsec.