Information of Sapphire Substrates Sapphire substrates are critical foundational materials for LEDs and GaN devices. Although its own market size (approximately USD 833 million globally by 2031) is relatively limited, it underpins downstream applications worth trillions of dollars, bearing strategic and pioneering significance. Upstream: High-purity alumina (mainly 4N5 and above), crystal growth equipment (such as Kyropoulos furnaces), and tungsten‑molybdenum thermal fields.