GaN growth using a low-temperature GaNP buffer on sapphire by metalorganic chemical vapor deposition

We developed a buffer layer to grow GaN epilayers by metalorganic chemical vapor deposition. The buffer layer consists of a thin GaN-rich GaNP layer deposited at low temperature (LT) (500 °C) on sapphire substrate, using phosphine (PH3) as the phosphorus source. For high-temperature GaN epilayers grown on this type of buffer, full-width at half maximum values from both (0002) and (101̄2) x-ray rocking curves decrease as phosphorus composition in the GaNP buffer increases; a dislocation density observed by transmission electron microscopy is as low as 5×108 cm−2, which is a factor of 2 less compared to that in a conventional GaN buffer epilayer. These results reveal that LT GaNP can be used as an appropriate buffer for further improving quality of GaN-based films.