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Advantages and remaining issues of state-of-the-art m-plane freestanding GaN (FS-GaN) substrates grown by halide vapor phase epitaxy (HVPE) for m-plane In x Ga 1−x N epitaxial film growth by metalorganic vapor phase epitaxy are described. Because of the low threading dislocation and basal-plane stacking fault densities, improved quantum efficiency and short radiative lifetime are achieved for the near-band-edge emission of 200-250 nm thick m-plane pseudomorphic In x Ga 1−x N (x 0.14) epilayers. Values of full-width at half-maximum for the x-ray ω-rocking curves remain unchanged as the substrate values being 80 and 60 arcsec for the (1010) diffraction with 0001 and 1120 azimuths, respectively, and 80 arcsec for the (1012) diffraction. As the surface flatness is greatly improved, the In-incorporation efficiency (η In inc ) is lower than the cases for conventional c-plane growth and m-plane growths on defective GaN bases. The former originates from nonidentical surface kinetics, and the latter is due to the reduction in the area of inclined and tilted planes. Sub-micrometer-wide zonary patterns parallel to the c-axis and 2 μm long axis figure-of-eight patterns parallel to the a-axis are clearly visualized in the monochromatic cathodoluminescence (CL) intensity images. Because the spatio-time-resolved CL measurement reveals very little spatial variation of low-temperature radiative lifetime, the slight peak energy variation is interpreted to originate from nonidentical η In inc for the growing surfaces exhibiting various miscut angles. The figure-of-eight patterns are ascribed to originate from the anisotropic, severe m-plane tilt mosaic along the a-axis of the GaN substrate, and the zonary patterns may originate from the m-plane tilt mosaic along the c-axis. Further reduction in the tilt and twist mosaics is necessary for HVPE of FS-GaN substrates, in order to grow homogeneous InGaN epilayers.

cathodoluminescence (STRCL) spectroscopy is implemented to assess the local carrier dynamics in a 70-nm-thick, very low threading dislocation (TD) density, pseudomorphic m-plane In 0:05 Ga 0:95 N epilayer grown on a freestanding GaN substrate by metalorganic vapor phase epitaxy. Although TDs or stacking faults are absent, sub-micrometer-wide zonary patterns parallel to the c-axis and 2-m-long-axis figureof-8 patterns parallel to the a-axis are clearly visualized in the monochromatic cathodoluminescence intensity images. Because the STRCL measurement reveals very little spatial variation of low-temperature radiative lifetime, the considerable peak energy variation is interpreted to originate from nonidentical In-incorporation efficiency for the growing surfaces exhibiting various miscut angles. The figure-of-8 patterns are ascribed to originate from the anisotropic, severe m-plane tilt mosaic along the a-axis of the GaN substrate, and the zonary patterns may originate from the m-plane tilt mosaic along the c-axis. #

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Reactions between a precursor-absorbed SiO2 surface and energetic ion species, i.e. Ar+ or O+ ions, in a plasma enhanced atomic layer deposition (PEALD) process were investigated using an in situ X-ray photoelectron spectrometer system and a molecular dynamics (MD) simulation. Both the experiment and simulation results showed that N and/or C atoms originating from the precursor molecules remained on the surface as amorphous carbon and/or cyanide after 50 eV ion bombardment. The precursor-originated atoms as well as the SiO2 film were removed by the incident ions when its energy increased to 100 eV, and exceedingly small amount remained on the surface. The MD simulation results showed that chemical effects had a more obvious effect on the removal of C atoms at lower incident energies, while purely physical effects dominated at high O+ ion incident energies. These results indicated the importance of ion energy in PEALD processes in terms of film quality.