Bulk AlN growth by physical vapour transport

The process technologies of AlN growth by physical vapour transport are reviewed in this paper with a focus on the growth parameters, crucible materials, and the type of seeding/nucleation. In this context the three growth strategies for the first generation of AlN seeds, (i) grain selection, (ii) heteroepitaxially seeding on SiC, and (iii) spontaneous nucleation, are evaluated regarding their impact on the structural properties and the sizes of the grown AlN crystals. Major issues for subsequent homoepitaxial growth runs with controlled diameter enlargement, such as thermal field design and seed fixation, are addressed. Furthermore, the influences of the growth conditions on the main optical absorption bands in AlN are discussed. (invited article)