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Phone: þ1-807-3438311, Fax: 1 201 839 4341InN thin films were grown by a new technique, migration enhanced afterglow (MEAglow), a chemical vapour deposition (CVD) form of migration enhanced epitaxy (MEE). Here we describe the apparatus used for this form of film deposition, which includes a scalable hollow cathode nitrogen plasma source. Initial film growth results for InN are also presented including atomic force microscopy (AFM) images that indicate step flow growth with samples having root mean square (RMS) surface roughness of as little as 0.103 nm in some circumstances for film growth on sapphire substrates. X-ray diffraction (XRD) results are also provided for samples with a full width half maximum (FWHM) of the (0002) v-2u peak of as little as 290 arcsec. Low pressure conditions that can result in damage to the InN during growth are described.1 Introduction We report on the initial results for indium nitride films grown by a new technique that we have coined migration enhanced afterglow (MEAglow) deposition. Traditionally in RF plasma MBE systems, for the migration enhanced epitaxy (MEE) of group III metal nitrides, the metal is deposited as a thin wetting layer on a substrate and is subsequently nitrided using a nitrogen plasma to form a thin nitride semiconductor layer. A number of cycles of metal deposition with subsequent nitriding are used to build up a thicker film. Past thought has limited the thickness of the metal layer used for each cycle because deposition of more than a couple of monolayers of metal at a time can result in the formation of metal droplets on the substrate surface. It was believed that the nitridation of metal droplets would be difficult at best. However, recently it has been shown that even with these droplets being present good quality InN film growth can be achieved using thick metal deposition in a process that may be similar in some respects to liquid phase epitaxy (LPE) [1].For the work presented here we have migrated these recent MEE results to a low pressure chemical vapour deposition (CVD) environment for the deposition of InN. A nitrogen plasma is also used in this situation, however the

Some initial results are presented for gallium nitride and indium nitride thin films grown on c‐plane sapphire using a prototype migration enhanced afterglow (MEAglow) system. Smooth surfaces of less than 1 nm root mean square surface roughness have been achieved for both InN and GaN films at growth temperatures of 450‐560 °C and 665 °C respectively. This result is attributed to the increased adatom diffusion length allowed for the metal species during the growth process. Thicker GaN layers can now be grown than those previously reported. For InN, an impressive full width half maximum value of 290 arcsec has been achieved for the (0002) reflection using ω−2θ X‐ray diffraction scans. Greater progress has so far been achieved for the growth of InN films because of the relative ease with which thick layers of indium metal can be nitrided to form a good quality layer. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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The effect of known growth artifacts on the absorption and photoluminescence properties of InN films is determined using linear combination of atomic orbitals electron band structure calculations. InxAl1−xN interfacial layers are examined for various atomic fractions of Al, since these layers are observed to be relatively thick (up to 100 nm) for thin films of InN deposited on AlN or sapphire. It is found that for penetration of Al atoms in InN, forming In-rich InxAl1−xN, a decrease of the energy band gap of InN occurs, despite AlN having a much larger band gap than InN. Γc13↔Γν154 exciton emissions for InxAl1−xN are found to have an energy of 0.765–0.778 eV and may explain recent photoluminescence data for InN. Optical absorption for this alloy is dominated by a 1.58–1.62 eV transition. The second artifact investigated here is high concentration oxygen impurity atoms in wurtzite InN. Segregated oxygen species are not considered, only alloyed species with oxygen substituting on the nitrogen site. For this arrangement a new ternary semiconductor InOyN1−y with y∼0.1 is identified. A model of the tetrahedral cell In–O is made and the energy band gap of InOyN1−y is calculated. It is found that the presence of O atoms in InN can decrease the energy band gap. Optical absorption as low as 1.19 eV can be evident. The exciton emissions Γc12↔Γν151 in InOyN1−y were found to vary in energy over the range 0.84–1.01 eV.

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