Gallium nitride is a substance that does not exist in nature and has to be synthesized completely by artificial synthesis. Gallium nitride has no liquid state, so it cannot be pulled out single crystal by the traditional straight pulling method of single crystal silicon production process, and it is synthesized purely by gas reaction. Due to the long reaction time, slow speed, many by-products, harsh equipment requirements, extremely complex technology, and extremely low production capacity, GaN single crystal material is extremely rare, so the price of 2 inches is more than 20,000. In commercial scenarios, GaN heterogeneous epitaxial wafers are more often used.
GaN crystals are difficult to fabricate.
When GaN material was first invented for blue LEDs, it was already found to be very difficult to make GaN crystals. Later, the research on wide band gap semiconductor materials became more advanced, and it was found that GaN material has high insulation resistance, which is suitable for making power devices, and thus the GaN charging head was born. However, the crystallinity of GaN is required for power devices. The issue of single-crystal GaN production, once avoided en masse, came back to the fore.
Unlike traditional Si materials, GaN cannot be grown single-crystalline by the CZ method. The prevailing production method is to produce a GaN film about 1 mm thick on other crystalline surfaces, then peel it off and polish it for use as a GaN substrate. This is a very low yield when compared with the ability to produce up to 2 m of Si in a single pull. When exfoliating heterogeneous crystals, stress buildup often leads to substrate rupture due to multiple crystals attached around the single crystals and internal crystallization defects. In fact, it can be said that mankind has not yet mastered the ability to produce GaN single crystals on a large scale.
Against this backdrop, GaN products are still being forced to be commercialized at a much higher price (compared to conventional Si semiconductors).
