@article{oktyabrsky_dovidenko_sharma_joshkin_narayan_1999, title={Crystal structure and defects in nitrogen-deficient GaN}, volume={4S1}, number={G6.43}, journal={MRS Internet Journal of Nitride Semiconductor Research}, author={Oktyabrsky, S. and Dovidenko, K. and Sharma, A. K. and Joshkin, V. and Narayan, J.}, year={1999} }
 @article{oktyabrsky_dovidenko_sharma_narayan_joshkin_1999, title={Cubic GaN formation under nitrogen-deficient conditions}, volume={74}, ISSN={["0003-6951"]}, DOI={10.1063/1.123882}, abstractNote={We have studied crystal structure and associated defects in GaN/α-Al2O3 (0001) films grown under nitrogen-deficient conditions by metalorganic chemical vapor deposition and pulsed laser deposition. N-deficient films exhibit polycrystalline structure with a mixture of cubic zinc-blende and wurtzite hexagonal GaN grains retaining tetragonal bonding across the boundaries and hence the epitaxial orientations and polarity. Renucleation of the wurtzite phase at different {111} planes of cubic GaN results in a rough and faceted surface of the film. We elucidate that the cubic phase is more stable under the nitrogen deficiency.}, number={17}, journal={APPLIED PHYSICS LETTERS}, author={Oktyabrsky, S and Dovidenko, K and Sharma, AK and Narayan, J and Joshkin, V}, year={1999}, month={Apr}, pages={2465–2467} }
 @article{joshkin_parker_bedair_muth_shmagin_kolbas_piner_molnar_1999, title={Effect of growth temperature on point defect density of unintentionally doped GaN grown by metalorganic chemical vapor deposition and hydride vapor phase epitaxy}, volume={86}, ISSN={["0021-8979"]}, DOI={10.1063/1.370727}, abstractNote={We report on the investigation of the effect of growth temperature on point defect density of unintentionally doped GaN grown by atmospheric pressure metalorganic chemical vapor deposition and hydride vapor phase epitaxy. A correlation between photoluminescence (PL) spectra and the concentration of donors and acceptors in unintentionally doped GaN is presented. The effects of oxygen and native acceptors on the electrical and optical properties of GaN epitaxial layers are discussed and a classification of PL data is presented. On this basis we show that oxygen creates a shallow donor in GaN with an activation energy of about 23.5±1 meV. We determine that the concentration of native acceptors in GaN increases with an increase in growth temperature. These native acceptors, probably gallium antisites (GaN) and/or gallium vacancies (VGa), are nonradiative defects. We show that a second donor level in GaN has an activation energy of about 52.5±2.5 meV and produces a PL peak with an energy of about 3.45 eV at lo...}, number={1}, journal={JOURNAL OF APPLIED PHYSICS}, author={Joshkin, VA and Parker, CA and Bedair, SM and Muth, JF and Shmagin, IK and Kolbas, RM and Piner, EL and Molnar, RJ}, year={1999}, month={Jul}, pages={281–288} }
 @article{joshkin_parker_bedair_krasnobaev_cuomo_davis_suvkhanov_1998, title={Fine structure of near-band-edge photoluminescence in He+-irradiated GaN grown on SiC}, volume={72}, ISSN={["0003-6951"]}, DOI={10.1063/1.121474}, abstractNote={The effect of He ion implantation on the optical properties of epitaxial GaN-on-SiC was studied. We observed that He+ irradiation increases the relative intensity of the “blue emission” and resistivity of GaN films and decreases the intensity of the near-band-edge photoluminescence. Because the intensity of the main peak is drastically decreased, the fine structure of the near-band-edge photoluminescence in GaN after He+ irradiation was observed. From a comparison of observed sharp lines with photoluminescence peaks of GaN doped with oxygen, we conclude that oxygen can produce a complex, which is characterized by a strong localization of free carriers and a large lattice distortion. The zero-phonon line of this defect has energy close to the band-gap energy of GaN.}, number={22}, journal={APPLIED PHYSICS LETTERS}, author={Joshkin, VA and Parker, CA and Bedair, SM and Krasnobaev, LY and Cuomo, JJ and Davis, RF and Suvkhanov, A}, year={1998}, month={Jun}, pages={2838–2840} }
 @article{joshkin_roberts_mcintosh_bedair_piner_behbehani_1997, title={Optical memory effect in GaN epitaxial films}, volume={71}, ISSN={["0003-6951"]}, DOI={10.1063/1.120414}, abstractNote={We report on memory effects in the optical properties of GaN and AlN epitaxial-films grown by atmospheric pressure metal organic chemical vapor deposition. After exposing selected areas of particular samples with He–Cd laser light (3.8 eV), we observed a persistent and marked decrease in the near band edge photoluminescence (PL) intensity emitted from these areas. This effect has been observed in epitaxial films that typically have a pyramidlike hillock surface. This ability to modulate PL emission intensity at individual points in these materials can be exploited as a method for optical data storage. A means of erasing information stored using this effect has also been investigated using lower energy (∼2 eV).}, number={2}, journal={APPLIED PHYSICS LETTERS}, author={Joshkin, VA and Roberts, JC and McIntosh, FG and Bedair, SM and Piner, EL and Behbehani, MK}, year={1997}, month={Jul}, pages={234–236} }