Uniform growth of ͑1-101͒GaN was performed on coalesced stripes of GaN which had been prepared by selective metalorganic vapor phase epitaxy on a 7°off-axis ͑001͒Si substrate via an AlN intermediate layer. The cathodoluminescence spectra at 4 K exhibited a donor bound excitonic emission at 358 nm followed by defect-related emission peaks at 363, 371, and 376 nm. The 363 and 376 emission bands are observed upon the coalescence region. The Hall measurements exhibited p-type conduction at 80-300 K ͑the hole carrier density 6.3ϫ10 12 cm Ϫ2 and hole mobility 278 cm 2 /V s at 100 K͒. The activation energy of the acceptor was estimated to be 60 meV. The possible origin of the p-type conduction is discussed in relation to the unintentionally doped carbon.
The growth of a trapezoidal AlGaN/GaN heterostructure was attempted on a (111) Si substrate by selective area metal organic vapour phase epitaxy. On the trapezoidal sample we found that the manner of ridge growth is different in GaN growth from that in AlGaN growth. Analysing the thickness and composition with scanning electron microscopy (SEM), reflection electron microscopy (REM) and cathode luminescence (CL) spectroscopy, the diffusion length of Ga chemical species on the (0001) AlGaN surface was determined.
Using a selective metal organic vapour phase epitaxy method, (1-101)GaN was grown on a (001)Si substrate. Intentional carbon doping was attempted using CCl 4 as the souce gas and the electrical properties were studied as a function of the doping level. All samples showed the p-type conduction. The hole concentration was increased by the doping, determined by the ratio of the carbon source and NH 3 flow rates. The results indecated that the p-type conduction is due to the incorporation of carbon in the (1-101)GaN.
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