Surface morphology evolution of m-plane ( 1 1 ¯ 00 ) GaN during molecular beam epitaxy growth: Impact of Ga/N ratio, miscut direction, and growth temperature J. Appl. Phys. 114, 023508 (2013) The effect of Ga/N flux ratio on surface morphology, incorporation of point defects and electrical transport properties of GaN films grown by plasma-assisted molecular beam epitaxy in a recently developed high-temperature growth regime was investigated. The homoepitaxial ͑0001͒ GaN films grown at ϳ780-790°C showed smoothest morphologies near the cross-over between N-rich and Ga-rich growth ͑0.75Ͻ Ga/ N Ͻ 1.1͒ contrasting previous observations for low-temperature growth.The higher-quality growth near Ga/ N ϳ 1 resulted from lower thermal decomposition rates and was corroborated by slightly lower Ga vacancy concentrations ͓V Ga ͔, lower unintentional oxygen incorporation, and improved electron mobilities. The consistently low ͓V Ga ͔, i.e., ϳ10 16 cm −3 for all films attribute further to the significant benefits of the high-temperature growth regime.

Vacancy-type defects in Si-doped InN grown by plasma-assisted molecular-beam epitaxy probed using monoenergetic positron beams

The introduction of vacancy type point defects by Si doping in InN grown by plasma-assisted molecular beam epitaxy was studied using a monoenergetic positron beam. With the combination of positron lifetime and Doppler broadening measurements, compensating In-vacancy (V In ) acceptors were identified in the material. For increasing Si doping an enhanced formation of V In defects was observed, up to a concentration of c V ¼ 7 Â 10 17 cm À3 in the highest doped sample (n e ¼ 6:6 Â 10 20 cm À3 ). A strong inhomogeneity of the defect profile with a significant increase of the V In concentration toward the layer/substrate interface could be detected. Additionally, larger vacancy clusters containing several V In are formed in the proximity of the interface.

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