Influence of NrGa-flux ratio on optical properties and surface morphology of GaN grown on sapphire 0001/by MBE

We studied the correlation between the low-temperature optical properties and the surface morphology of molecular beam epitaxy MBE.grown GaN on sapphire 0001.. The samples were grown under Ga-rich conditions, with the Ga-flux as a parameter, and with all other growth parameters constant. High-resolution scanning electron microscopy SEM.provided a measure of the surface morphology, while the optical properties were characterised by low-temperature photoluminescence. These spectra were dominated by the exciton bound to neutral donor transition, at 3.472–3.474 eV, indicating fairly strain relaxed layers. This peak width is increased when the surface morphology improved. Our results also showed a clear correlation between the optical properties and the purity of the nitrogen source, as improved oxygen purification improved the photoluminescence linewidth from 41 to 20 meV. q2000 Elsevier Science B.V. All rights reserved.