High quality GaN grown at high growth rates by gas-sourcemolecular beam epitaxy

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Abstract
High quality GaN has been grown by gas-source molecular beam epitaxy (MBE) using ammonia as the nitrogen source. A growth rate as high as 1 µm/h, which is an order of magnitude higher than previously reported for the growth of GaN by MBE, has been achieved. Strong reflection high-energy electron diffraction (RHEED) intensity oscillations have been observed during the growth, making in situ thickness monitor and control as thin as one monolayer possible. The undoped GaN demonstrated an unintentional n-type carrier density of 2 × 1017 cm-3 and an electron Hall mobility of 110 cm2/V.s, the best ever achieved by MBE. For Mg-doped p-type GaN films a hole density of 4 × 1017 cm-3 and hole mobility of 15 cm2/V.s were achieved without post-growth annealing. Low temperature photoluminescence of as-grown materials was dominated by band-edge emissions, indicative of high quality materials which are promising for applications to blue light emitters and high-temperature electronic devices.