Homoepitaxial growth of 3-inch single crystalline AlN boules by the physical vapor transport process

Abstract

Single crystalline aluminum nitride (sc-AlN or AlN) boules with a diameter of 3-inch (Φ76 mm) were successfully prepared by the physical vapor transport (PVT) process. The initial homoepitaxial growth run was performed on an aluminum nitride seed sliced from a Φ51 mm aluminum nitride boule, and diameter enlargement was conducted iteratively via the lateral expansion technique until a Φ76 mm boule was achieved. During the diameter expansion growth runs, the crystal shape transitioned from a hexagonal pyramid to a cylindrical pyramid. After the standard slicing and wafering processes, the as-obtained substrates were characterized by high-resolution X-ray diffraction (HRXRD), preferential chemical etching, and optical spectroscopy. The characterization results revealed that the aluminum nitride substrates showed good crystallinity and excellent UV transparency, although a slight quality deterioration was observed when the crystal size was expanded from Φ51 to Φ76 mm, while the deep-UV (DUV) transparency remained very similar to that of the aluminum nitride seeds. The Φ76 mm aluminum nitride boules obtained in this study are an important milestone towards achieving Φ100 mm (4-inch) aluminum nitride, which are essential for the rapid commercialization of deep-UV optoelectronics and ultra-wide bandgap (UWBG) electronics.