Optical and structural properties of BGaN layers grown on different substrates

Growth of BGaN epitaxial layers by metalorganic chemical vapor deposition (MOCVD) using triethylboron (TEB) as a boron source was studied on 6H-SiC substrate and on GaN and AlN templates on sapphire. X-ray diffraction, atomic force microscopy and photoluminescence spectroscopy were exploited to characterize the structural quality, surface morphology, luminescence efficiency, and boron content. Silicon carbide was shown to be slightly superior to AlN/sapphire and considerably better than GaN/sapphire as the most favorable substrate to incorporate a possibly higher boron content. Increasing TEB flow rate at correspondingly optimized growth temperature and V/III ratio enabled us to achieve the boron content of up to 5.5%, though at the expense of structural quality. We showed that the band gap bowing parameter is similar for the epilayers deposited on all the three templates/substrates under study and is approximately equal to 4 eV, substantially lower than reported before.