NOVELTY - Growing bulk single crystals of aluminum nitride (AlN) on a single crystal seed (68) involves providing a crucible (20) having removable cap (28); fusing a single crystal seed to a surface of cap that faces interior of crucible chamber; placing an AlN source material in the chamber in spaced relation to seed fused to cap; heating crucible to establish a temperature gradient between source material and seed, where the seed is at a higher temperature than the source material to evaporate an outer layer of the seed; and inverting temperature gradient between source material and seed.    USE - For growing bulk single crystals of aluminum nitride (AlN) on a single crystal seed for preparing aluminum nitride single substrate useful in e.g. light emitters such as light emitting device and laser diodes, light detector, and high power and/or high-frequency transistors.    ADVANTAGE - The process is capable of removing contaminants on exposed surface of the seed, as well as removing surface and sub-surface damage caused by cutting, grinding, or polishing during the seed fabrication process. The process establishes temperature gradient between the source material and the seed where seed is maintained at a higher temperature, for facilitating evaporation of an outer layer of the seed while preventing deposition of the source material onto the damaged or contaminated surface of the seed. The method firmly affixes seed to the crucible cap without using high temperature glues/binders or mechanical clamping structures, which can introduce sources of contamination into the process and which fail to provide maximal thermal contact between the seed and the crucible cap. The process enables homoepitaxial growth of high quality aluminum nitride (AlN) crystals on AlN seeds of any given crystallographic orientation. The process allows growth process interruptions and consecutive resumption of epitaxial growth on the previous growth front while suppressing unwanted, secondary nucleation that would otherwise adversely affect the crystal quality; and enables the preparation of large-size, single crystalline AlN boules through iterative regrowth on previously deposited material without losing the crystallographic relationship between the previously deposited growth and overgrown material. The process provides an integrated process route for batch-process boule production during which a slice or wafer cut from a previously grown boule is used as a seed for the growth of the next boule.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) securing single crystal seed to crucible involving subliming aluminum nitride source material to deposit a condensed polycrystalline mass of the material on an internal surface of chamber, placing a single crystal seed on a surface of the cap facing the interior of chamber, closing open end of chamber with the cap carrying the seed, and heating the crucible chamber to fuse the seed to cap; and an aluminum gallium nitride device comprising AlN substrate.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic representation of process for growing bulk single crystals of aluminum nitride.    crucible (20)    removable cap (28)    polycrystalline mass (64)    single crystal seed. (68)