@article{balkas_sitar_bergman_shmagin_muth_kolbas_nemanich_davis_2000, title={Growth and characterization of GaN single crystals}, volume={208}, ISSN={["0022-0248"]}, DOI={10.1016/S0022-0248(99)00445-5}, abstractNote={Up to 3 mm long GaN single crystals were grown by sublimation of cold pressed GaN pellets or evaporation of gallium (Ga) metal under an ammonia (NH3) flow in a dual heater, high-temperature growth system. A growth rate of 500 μm/h along the [0 0 0 1] direction was achieved using a source temperature of 1200°C, a total pressure of 760 Torr, and an NH3 flow rate of 50 sccm. The resulting crystals were transparent, possessed low aspect ratios and well-defined growth facets. The only impurity present at high concentrations was oxygen (3×1018 atoms/cm3). Photoluminescence studies conducted at 77 K showed a sharp emission peak centered at 359 nm. Time-dependent photoluminescence measurements revealed optical metastability in bulk GaN. Raman spectroscopy yielded narrow peaks representing only the modes allowed for the wurtzite structure. All characterization studies confirmed excellent crystalline and optical quality of the obtained single crystals.}, number={1-4}, journal={JOURNAL OF CRYSTAL GROWTH}, author={Balkas, CM and Sitar, Z and Bergman, L and Shmagin, IK and Muth, JF and Kolbas, R and Nemanich, RJ and Davis, RF}, year={2000}, month={Jan}, pages={100–106} }
 @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 low temperatures. From Hall investigations we show that a third donor in GaN has an activation energy of 110±10 meV.}, 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} }
 @misc{shmagin_muth_kolbas_1999, title={Optical information storage systems and methods using heterostructures comprising ternary group III-V nitride semiconductor materials}, volume={5,875,052}, number={1999 Feb. 23}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Shmagin, I. K. and Muth, J. F. and Kolbas, R. M.}, year={1999} }
 @inproceedings{dupuis_grudowski_eiting_shmagin_kolbas_rosner_1998, title={Optical and structural characterization of InGaN quantum-well heterostructures grown by metalorganic chemical vapor deposition}, booktitle={Compound semiconductors 1997: Proceedings of the IEEE Twenty-fourth International Symposium on Compound Semiconductors held in San Diego, California, 8-11 September 1997}, publisher={Bristol; Philadelphia: Institute of Physics Pub.}, author={Dupuis, R. D. and Grudowski, P. A. and Eiting, C. J. and Shmagin, I. K. and Kolbas, R. M. and Rosner, S. J.}, year={1998}, pages={231–234} }
 @inproceedings{shmagin_muth_kolbas_dupuis_grudowski_eiting_park_shelton_lambert_1998, title={Optical metastability in InGaN/GaN heterostructures}, booktitle={Compound semiconductors 1997: Proceedings of the IEEE Twenty-fourth International Symposium on Compound Semiconductors held in San Diego, California, 8-11 September 1997}, publisher={Bristol; Philadelphia: Institute of Physics Pub.}, author={Shmagin, I. K. and Muth, J. F. and Kolbas, R. M. and Dupuis, R. D. and Grudowski, P. A. and Eiting, C. J. and Park, J. and Shelton, B. S. and Lambert, D. J. H.}, year={1998}, pages={375–378} }
 @inproceedings{kolbas_shmagin_muth_1998, title={Optical properties of wide bandgap II-V nitride semiconductors}, booktitle={1998 5th International Conference on Solid-State and Integrated Circuit Technology: Proceedings, October 21-23, 1998, Beijing, China}, author={Kolbas, R. M. and Shmagin, I. K. and Muth, J. F.}, editor={M. Zhang and Tu, K. N.Editors}, year={1998}, pages={609–612} }
 @article{osinsky_gangopadhyay_yang_gaska_kuksenkov_temkin_shmagin_chang_muth_kolbas_1998, title={Visible-blind GaN Schottky barrier detectors grown on Si(111)}, volume={72}, ISSN={["0003-6951"]}, DOI={10.1063/1.120755}, abstractNote={We report novel GaN detectors grown by molecular beam epitaxy on Si(111) substrates. Wurtzite structure epitaxial GaN exhibits room-temperature photoluminescence with a band-edge-related emission width as narrow as 7 nm and intensities comparable to high quality layers grown on sapphire by metalorganic chemical vapor deposition. Spectral response of lateral geometry Schottky detectors shows a sharp cutoff at 365 nm with peak responsivities of ∼0.05 A/W at 0 V, and ∼0.1 A/W with a −4 V bias. The dark current is ∼60 nA at −2 V bias. The noise equivalent power is estimated to be 3.7×10−9 W over the response bandwidth of 2.2 MHz.}, number={5}, journal={APPLIED PHYSICS LETTERS}, author={Osinsky, A and Gangopadhyay, S and Yang, JW and Gaska, R and Kuksenkov, D and Temkin, H and Shmagin, IK and Chang, YC and Muth, JF and Kolbas, RM}, year={1998}, month={Feb}, pages={551–553} }
 @article{muth_lee_shmagin_kolbas_casey_keller_mishra_denbaars_1997, title={Absorption coefficient, energy gap, exciton binding energy, and recombination lifetime of GaN obtained from transmission measurements}, volume={71}, ISSN={["0003-6951"]}, DOI={10.1063/1.120191}, abstractNote={The absorption coefficient for a 0.4-μm-thick GaN layer grown on a polished sapphire substrate was determined from transmission measurements at room temperature. A strong, well defined exciton peak for the A and B excitons was obtained. The A, B, and C excitonic features are clearly defined at 77 K. At room temperature, an energy gap Eg=3.452±0.001 eV and an exciton binding energy ExA,B=20.4±0.5 meV for the A and B excitons and ExC=23.5±0.5 meV for the C exciton were determined by analysis of the absorption coefficient. From this measured absorption coefficient, together with the detailed balance approach of van Roosbroek and Shockley, the radiative constant B=1.1×10−8 cm3/s was obtained.}, number={18}, journal={APPLIED PHYSICS LETTERS}, author={Muth, JF and Lee, JH and Shmagin, IK and Kolbas, RM and Casey, HC and Keller, BP and Mishra, UK and DenBaars, SP}, year={1997}, month={Nov}, pages={2572–2574} }
 @article{keller_keller_kapolnek_mishra_denbaars_shmagin_kolbas_krishnankutty_1997, title={Growth of bulk InGaN films and quantum wells by atmospheric pressure metalorganic chemical vapour deposition}, volume={170}, ISSN={["0022-0248"]}, DOI={10.1016/S0022-0248(96)00553-2}, abstractNote={InGaN bulk layers and single quantum wells were grown on 1.4 to 2.4 μm thick GaN on sapphire films by atmospheric pressure metalorganic chemical vapour deposition (AP-MOCVD). The morphology of the epitaxial layers was strongly affected by the VIII ratio in the gas phase. The incorporation efficiency of indium was observed to increase with higher growth rates and decreasing temperature, but was independent of the VIII ratio in the investigated parameter range. In0.16Ga0.84N single quantum wells showed intense quantum well related luminescence at room temperature, with a full width at half maximum of 7.9 nm at a thickness of 50 Å. Single quantum wells embedded in InGaN of graded composition showed superior properties compared to quantum wells with In0.04Ga0.94N barriers of constant composition.}, number={1-4}, journal={JOURNAL OF CRYSTAL GROWTH}, author={Keller, S and Keller, BP and Kapolnek, D and Mishra, UK and DenBaars, SP and Shmagin, IK and Kolbas, RM and Krishnankutty, S}, year={1997}, month={Jan}, pages={349–352} }
 @article{shmagin_muth_kolbas_krishnankutty_keller_mishra_denbaars_1997, title={Observation of lasing from photopumped InGaN/GaN heterostructures in an edge emitting configuration}, volume={81}, ISSN={["0021-8979"]}, DOI={10.1063/1.364058}, abstractNote={Optically pumped lasing from InGaN/GaN single heterojunctions (SH) was observed in an edge emitting configuration at 77 K. The heterojunctions were grown by atmospheric pressure metalorganic chemical vapor deposition on c-plane sapphire substrates. The frequency tripled output of a mode-locked titanium:sapphire laser with a pulse width of 250 fs, operating at 280 nm, was used as the photoexcitation source. The nonlinear dependence of output emission intensity on input power density, the observations of a strongly polarized output emission, and distinct Fabry–Perot modes are discussed.}, number={4}, journal={JOURNAL OF APPLIED PHYSICS}, author={Shmagin, IK and Muth, JF and Kolbas, RM and Krishnankutty, S and Keller, S and Mishra, UK and DenBaars, SP}, year={1997}, month={Feb}, pages={2021–2023} }
 @article{shmagin_muth_kolbas_dupuis_grudowski_eiting_park_shelton_lambert_1997, title={Optical data storage in InGaN/GaN heterostructures}, volume={71}, ISSN={["0003-6951"]}, DOI={10.1063/1.119900}, abstractNote={Optical storage data was realized using an InGaN/GaN single heterostructure. It was observed that exposure to a high power density ultraviolet light temporarily changes the optical properties of the InGaN epitaxial layer. The photo-induced changes can be observed under an optical microscope with low intensity ultraviolet excitation. This effect was used to create high contrast optical patterns on the sample at room temperature and 77 K. The photo-induced changes completely disappear in about four hours at room temperature. After the recorded pattern is erased, the information can be rewritten without a change in efficiency or retention time.}, number={10}, journal={APPLIED PHYSICS LETTERS}, author={Shmagin, IK and Muth, JF and Kolbas, RM and Dupuis, RD and Grudowski, PA and Eiting, CJ and Park, J and Shelton, BS and Lambert, DJH}, year={1997}, month={Sep}, pages={1382–1384} }
 @article{shmagin_muth_lee_kolbas_balkas_sitar_davis_1997, title={Optical metastability in bulk GaN single crystals}, volume={71}, ISSN={["0003-6951"]}, DOI={10.1063/1.119577}, abstractNote={Bulk GaN single crystals were grown from cold pressed GaN powder by sublimation in flowing ammonia. Optical transmission measurements indicated that the absorption coefficient for the transparent samples is 50 cm−1 in the wavelength region from 650 to 400 nm. Optical metastability in bulk GaN crystals was studied through time dependent photoluminescence both at room and liquid–nitrogen temperatures. The observation included decreasing output intensity of the ultraviolet emission attributed to the band edge and increasing output intensity of a new emission band centered at 378 nm at room temperature. At liquid–nitrogen temperature, the photoinduced emission band consisted of at least one LO-phonon replica of the zero-phonon line centered at 378 nm. The ratio of output intensities of the photoinduced band to the band edge increased by a factor of 10 during 27 min of exposure time. The photoinduced effect is attributed to the metastable nature of traps in bulk GaN.}, number={4}, journal={APPLIED PHYSICS LETTERS}, author={Shmagin, IK and Muth, JF and Lee, JH and Kolbas, RM and Balkas, CM and Sitar, Z and Davis, RF}, year={1997}, month={Jul}, pages={455–457} }
 @article{shmagin_muth_kolbas_krishnankutty_keller_abare_coldren_mishra_denbaars_1997, title={Photoluminescence characteristics of GaN/InGaN/GaN quantum wells}, volume={26}, ISSN={["0361-5235"]}, DOI={10.1007/s11664-997-0172-y}, number={3}, journal={JOURNAL OF ELECTRONIC MATERIALS}, author={Shmagin, IK and Muth, JF and Kolbas, RM and Krishnankutty, S and Keller, S and Abare, AC and Coldren, LA and Mishra, UK and DenBaars, SP}, year={1997}, month={Mar}, pages={325–329} }
 @article{shen_shmagin_koch_kolbas_fahmy_bergman_nemanich_mcclure_sitar_quan_1997, title={Photoluminescence from mechanically milled Si and SiO2 powders}, volume={55}, ISSN={["0163-1829"]}, DOI={10.1103/physrevb.55.7615}, abstractNote={The photoluminescence (PL) in as-received and milled Si and SiO2 powder is reported. The Si and SiO2 powder is characterized by chemical analysis, Raman scattering, x-ray photoelectron spectra, infrared absorption, x-ray diffraction, and differential thermal analysis. The results indicate that the Si powder has amorphous Si oxide and suboxide surface layers. The milling of Si powder results in the formation of nanocrystalline/amorphous Si components. An amorphous SiO2 component is formed by milling crystalline SiO2. The PL spectra for as-received Si, milled Si, and SiO2 powder exhibit similar peak shapes, peak maxima, and full width at half maximum values. For both the as-received and the milled Si powder, experimental results appear to exclude mechanisms for PL related to an amorphous Si component or Si-H or Si-OH bonds, or the quantum confinement effect. Similarly, for milled SiO2 powder mechanisms for PL do not appear related to Si-H or Si-OH bonds. Instead the greatly increased intensity of PL for milled SiO2 can be related to both the increased volume fraction of the amorphous SiO2 component and the increased density of defects introduced in the amorphous SiO2 upon milling. It is suggested that the PL for as-received Si, milling-induced nanocrystalline/amorphous Si, and milled SiO2 results from defects, such as the nonbridging oxygen hole center, in the amorphous Si suboxide and/or SiO2 components existing in these powder samples. The PL measurement for milled SiO2 is dependent on air pressure whereas that for as-received SiO2 is not, suggesting that new emitting centers are formed by milling.}, number={12}, journal={PHYSICAL REVIEW B}, author={Shen, TD and Shmagin, I and Koch, CC and Kolbas, RM and Fahmy, Y and Bergman, L and Nemanich, RJ and McClure, MT and Sitar, Z and Quan, MX}, year={1997}, month={Mar}, pages={7615–7623} }
 @article{shmagin_muth_kolbas_mack_abare_keller_coldren_mishra_denbaars_1997, title={Reconfigurable optical properties in InGaN/GaN quantum wells}, volume={71}, ISSN={["0003-6951"]}, DOI={10.1063/1.119935}, abstractNote={Reconfigurable optical properties were studied in InGaN/GaN multiple quantum well (MQW) structures. It was observed that a short time exposure to a high intensity ultraviolet light results in long term, but reversible changes of the optical properties of InGaN/GaN MQW samples. The photoinduced changes can be observed using an optical microscope under low intensity ultraviolet light and are visible as a high contrast pattern. The retention time at room temperature for 12 and 20 MQW samples was longer than five days and four weeks, respectively. The effect was studied at room and cryogenic temperatures.}, number={11}, journal={APPLIED PHYSICS LETTERS}, author={Shmagin, IK and Muth, JF and Kolbas, RM and Mack, MP and Abare, AC and Keller, S and Coldren, LA and Mishra, UK and DenBaars, SP}, year={1997}, month={Sep}, pages={1455–1457} }
 @inproceedings{balkas_sitar_zheleva_bergman_shmagin_muth_kolbas_nemanich_davis_1996, title={Growth of bulk AIN and GaN single crystals by sublimation}, booktitle={III-V nitrides: symposium held December 2-6, 1996, Boston, Massachusetts, U.S.A.  (Materials Research Society symposia proceedings ; v. 449)}, publisher={Pittsburgh, Pa.: Materials Research Society}, author={Balkas, C. M. and Sitar, Z. and Zheleva, T. and Bergman, L. and Shmagin, I. K. and Muth, J. F. and Kolbas, R. M. and Nemanich, R. and Davis, R. F.}, year={1996}, pages={41–46} }
 @inbook{shmagin_muth_kolbas_krishnankkutty_keller_mishra_denbaars_1996, title={Stimulated emission and gain measurements from InGaN/GaN heterostructures}, booktitle={III-V nitrides: Symposium held December 2-6, 1996, Boston, Massachusetts, U.S.A.(Materials Research Society symposia proceedings ; v. 449)}, publisher={Pittsburgh, Pa.: Materials Research Society}, author={Shmagin, I. K. and Muth, J. F. and Kolbas, R. M. and Krishnankkutty, S. and Keller, S. and Mishra, U. K. and DenBaars, S. P.}, year={1996}, pages={1209–1214} }