1. GaN Substrate Material for III–V Semiconductor Epitaxy Growth

The rapid commercialization of III-nitride semiconductor devices for applications in visible and ultraviolet optoelectronics and in high-power and high-frequency electronics accelerates the research, development, and commercial production of GaN substrate materials. GaN substrate with low defect density will be conducive to improve the performance and lifetime of the devices, leading to significant progress in the development of several optoelectronic and high-power devices. In this paper, various fabrication techniques and their corresponding development, considered with high potential to deliver high-quality and/or cost-effective and scalable GaN crystals, are reviewed, including liquid-phase methods and gas-phase methods. Among these growth methods, hydride vapor-phase epitaxy (HVPE) is well known as the major substrate technology with high growth rate, high crystal quality, and low cost, which attracts more attention. So, we have a special discussion on the detailed technological aspects of HVPE for the production of GaN substrate materials.