An Oxygen Doped Nucleation Layer for the Growth of High Optical Quality GaN on Sapphire

Abstract

We present a new oxygen-doped AlN nucleation layer for the growth of high quality GaN on sapphire by metalorganic vapor phase epitaxy. We investigated in detail the influence of oxygen in the gas phase in a range from 0.5 to 10 ppm. Around 4 ppm we obtained very stable and reproducible process conditions. A further optimization of the nucleation thickness resulted in GaN layers showing smooth and featureless surfaces with excellent spectroscopic properties. The best values were 45 arcsec in XRD rocking curve of the (002) peak and 1.7 meV in low temperature photoluminescence (PL) of the donor bound exciton. No yellow luminescence even at room temperature could be detected. Because of the low FWHM in PL a lot of features near the bandgap of GaN could be resolved. We observed the donor and acceptor bound exciton as well as the free A, B and C exciton.