Epitaxial growth of nitride semiconductors and their devices
The nitride semiconductor InGaAlN, known for blue light-emitting-diodes LEDs), has realized white LEDs for lighting and transistors for the base stations of cellar phones. However, there is no commercially available substrate of a nitride semiconductor itself.
At present, the cystals of nitride semiconductors have been grown on foreign substrates, and the density of threading dislocations (TDD) is as high as 108/cm2, which is extremely poor compared with TDD less than 103/cm2 for conventional semiconductors. Moreover, The crystal structure of all the conventional semiconductors applied for devices is cubic, whereas a nitride semiconductor is hexagonal, but their characteristics are not fully employed at present.
Our laboratory has possessed the fabrication technology of devices based on controlling the crystal polarity that is unprecedented in the world. By developing this technology, we are conducting the research on the fabrication of GaN single-crystal substrates, high-frequency and high-power transistors for post-5G applications (patent pending), UV light sources for sterilization, and high-power semiconductor lasers for machining.