Efficient diameter enlargement of bulk AlN single crystals with high structural quality

We present the growth of bulk AlN crystals by physical vapor transport and the structural characterization by various X-ray techniques and defect-selective etching. Starting from native AlN seeds with 8 mm in diameter we show a fast increase of the crystal diameters with expansion angles of about 45 degrees. Only two subsequent grown seeded crystals are required to reach crystals up to 34 mm in diameter. The threading dislocation density is below 10(4) cm(-2). The process outlines a shortcut path to industrially relevant AlN crystal diameters compared to all other published expansion processes for bulk AlN crystals so far. (c) 2023 The Author(s). Published on behalf of The Japan Society of Applied Physics by IOP Publishing Ltd