Homoepitaxial growth of 3-inch single crystalline AlN boules by the physical vapor transport process
Qikun Wang, Dan Lei, Jiali Huang, Xiaojuan Sun, Dabing Li, Zhenxiang Zhou, Liang Wu
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.