Comparison of the Physical Properties of GaN Thin Films Deposited on (0001) and(0112) Sapphire Substrates

摘要

Gallium nitride (GaN) is one of the most promising wide-gap III-V semiconductorsfor optical devices in the region of blue to ultraviolet light, because it has a direct band gap of 3.39 eV and high external photoluminescence quantum efficiency. It has been very difficult to obtain high-quality GaN films because of the large lattice mismatch and the large difference in the thermal expansion coefficient between GaN and substrates. Numerous substrate materials have been used for the deposition of GaN. For lack of an ideal substrate, nearly all the GaN has been grown on sapphire substrates despite its poor structural and thermal match.