MOCVB growth of GaBN on 6H-SiC (0001) substrates

BxGa1-xN films were deposited on 6H-SiC (0001) substrates at 1000 degrees C by low pressure MOVPE using diborane, trimethylgallium, and ammonia as pre cursors. The presence of boron was detected by Auger scanning microprobe, t he shift of the (00.2) x-ray diffraction peak, and low-temperature photolum inescence. A single-phase BxGa1-xN alloy with x = 1.5% was produced at the gas phase B/Ga ratio of 0.005. Phase separation into wurtzite BGaN and the B-rich phase occurred for a B/Ga ratio in the 0.01-0.2 range. Only BN was f ormed for B/Ga > 0.2. The B-rich phase was identified as h-BN with sp(2) bo nding based on the results of Fourier transform infrared spectroscopy. As t he diborane flow exceeds the threshold concentration, the growth rate of BG aN decreases sharply, because the growth of GaN is poisoned by the formatio n of the slow growing BN phase. The bandedge emission of BxGa1-xN varies fr om 3.45 1 eV for x = 0% with FWHM of 39.2 meV to 3.465 eV for x = 1.5% with FWHM of 35.1 meV. The narrower FWHM indicates that the quality of GaN epil ayer is improved with a small amount of boron incorporation. The PL linewid ths become broader as more boron is introduced into the solid solution.