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

Abstract

B_xGa_1−xN films were deposited on 6H-SiC (0001) substrates at 1000°C by low pressure MOVPE using diborane, trimethylgallium, and ammonia as precursors. The presence of boron was detected by Auger scanning microprobe, the shift of the (00.2) x-ray diffraction peak, and low-temperature photoluminescence. A single-phase B_xGa_1−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 formed for B/Ga >0.2. The B-rich phase was identified as h-BN with sp² bonding based on the results of Fourier transform infrared spectroscopy. As the diborane flow exceeds the threshold concentration, the growth rate of BGaN decreases sharply, because the growth of GaN is poisoned by the formation of the slow growing BN phase. The bandedge emission of B_xGa_1−xN varies from 3.451 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 epilayer is improved with a small amount of boron incorporation. The PL linewidths become broader as more boron is introduced into the solid solution.