High quality cubic GaN films were successfully grown on an AlN/GaN ordered alloy by RF-MBE. AlN/GaN ordered alloy is here employed instead of a AlGaN nucleation layer formed by nitridation of an AlGaAs buffer layer. Dominant cubic GaN epilayer (1.0 μm) growth was confirmed by insitu RHEED observations, AFM, TEM, PL and X-ray diffraction measurements.

. Hg; 78.66.Fd; 81.05.Ea; 81.15.Hi Cubic GaN films were grown on GaAs (100) using a newly introduced AlN/GaN ordered alloy fabricated by plasma-assisted molecular beam epitaxy. Dominant cubic GaN growth was confirmed by in situ reflection high-energy electron diffraction observations, photoluminescence (14 K) and X-ray diffraction measurements.Introduction Cubic GaN is expected to have lower resistivity and higher doping efficiency than the hexagonal phase due to its higher crystal symmetry. If high-quality c-GaN thin-film growth is realized, better performance of devices such as light emitting diodes (LEDs) and laser diodes (LDs) will be achievable.In earlier work we reported that using an AlGaN layer formed by the nitridation of an Al 0.17 Ga 0.83 As buffer layer was an efficient process for ensuring growth of a highpurity c-GaN film [1,2]. However, there still remain some problems regarding AlGaAs growth. The first relates to the fluctuation of Al molar content, which in turn affects significantly the purity of the structural phase of the epilayer. The second is the difficulty of maintaining high-quality stoichiometric growth for an extended period of time because careful control of each beam flux (Al, Ga and As) is required.In this work, a newly developed AlN/GaN ordered alloy (OA) is employed as a buffer layer. It is expected that a uniform effective Al molar content can be maintained by varying the ratio of each layer thickness. This process makes it easier to obtain highquality stoichiometric growth for extended periods because all constituent layers are binary materials. By the use of an OA buffer layer, the effective Al molar content can be kept low enough to prevent both the generation of hexagonal nuclei and the concomitant high resistivity by careful thickness control of each layer in the ultrathin region.High-quality c-GaN film growth was achieved using an AlN/GaN OA on GaAs by plasma-assisted molecular beam epitaxy (RF-MBE). Detailed X-ray diffraction (XRD) measurements, such as w scans, reciprocal area maps and pole figures, were carried out on the c-GaN epilayer. As no mixing of the hexagonal phase could be detected by these measurements, it was concluded that almost 100% phase purity was obtained.

Cubic GaN films on GaAs (100) were successfully grown using a newly introduced AlN/GaN ordered alloy (OA) and plasma-assisted molecular beam epitaxy. The epilayer quality was obtained by using a (AlN) 1 (GaN) 9 OA buffer layer (the numbers represent the number of monolayers). Dominant cubic GaN growth was confirmed by in-situ RHEED observation, photoluminescence (14 K) and X-ray diffraction measurements.

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