Research on the Micromorphology of the Native Surface of 2-Inch Aluminum Nitride Single Crystals

High-quality 2-inch aluminum nitride (AlN) crystals were grown using a double-zone resistance heating system, and the growth mechanism of AlN bulk crystals was further investigated. It was found that during the growth process, the vapor pressure at the growth interface, as well as the quality and structure of the seed crystal, was closely related to the growth conditions. The 2-inch AlN crystals were characterized using high-resolution X-ray diffraction (HRXRD) and optical microscopy. Optical microscopy observations of different regions on the native surface of the crystals revealed several morphologies, including regular step flow, irregular step flow, and domain-like structures. Comparisons showed that areas of the crystal surface with regular step-flow morphology exhibited high crystal quality, whereas the crystal quality decreased progressively as the step-flow morphology diminished. Therefore, the crystal quality can be preliminarily assessed through the surface morphology, providing guidance for improving the crystal growth process.