@misc{nagy_borges_brown_chaudhari_cook_hanson_johnson_linthicum_piner_rajagopal_et al._2008, title={Gallium nitride material transistors and methods associated with the same}, volume={7,352,016}, number={2008 Apr. 1}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Nagy, W. H. and Borges, R. M. and Brown, J. D. and Chaudhari, A. D. and Cook, J. W. and Hanson, A. W. and Johnson, J. W. and Linthicum, K. J. and Piner, E. L. and Rajagopal, P. and et al.}, year={2008} }
 @article{al-ajmi_kolbas_roberts_rajagopal_cook_piner_linthicum_2007, title={Room temperature laser action from multiple bands in photoexcited GaN grown on a silicon substrate}, volume={90}, number={15}, journal={Applied Physics Letters}, author={Al-Ajmi, F. S. and Kolbas, R. M. and Roberts, J. C. and Rajagopal, P. and Cook, J. W. and Piner, E. L. and Linthicum, K. J.}, year={2007} }
 @article{tanner_loebach_cook_hallen_2001, title={A pulsed jumping ring apparatus for demonstration of Lenz's law}, volume={69}, ISSN={["0002-9505"]}, url={http://dx.doi.org/10.1119/1.1376377}, DOI={10.1119/1.1376377}, abstractNote={Lenz’s law is often demonstrated in classrooms by the use of Elihu Thomson’s jumping ring. However, it is ironic that a thorough analysis of the physics of the ac jumping ring reveals that the operation is due mainly to a phase difference, not Lenz’s law. A complete analysis of the physics behind the ac jumping ring is difficult for the introductory student. We present a design for a pulsed jumping ring which can be fully described by the application of Lenz’s law. Other advantages of this system are that it lends itself to a rigorous analysis of the force balances and energy flow. The simple jumping ring apparatus closely resembles Thomson’s, but is powered by a capacitor bank. The jump heights were measured for several rings as a function of energy stored in the capacitors. A simple model describes the data well. Currents in both the drive coil and ring are measured and that of the drive coil modeled to illuminate some properties of the capacitors. An analysis of the energy flow in the system explains the higher jump heights, to 2 m, when the ring is cooled.}, number={8}, journal={AMERICAN JOURNAL OF PHYSICS}, author={Tanner, P and Loebach, J and Cook, J and Hallen, HD}, year={2001}, month={Aug}, pages={911–916} }
 @article{johnson_yu_brown_koeck_el-masry_kong_edmond_cook_schetzina_1999, title={A critical comparison between MOVPE and MBE growth of III-V nitride semiconductor materials for opto-electronic device applications}, volume={4S1}, DOI={10.1557/s1092578300003100}, abstractNote={A systematic study of the growth and doping of GaN, AlGaN, and InGaN by both molecular beam epitaxy (MBE) and metal-organic vapor phase epitaxy (MOVPE) has been performed. Critical differences between the resulting epitaxy are observed in the p-type doping using magnesium as the acceptor species. MBE growth, using rf-plasma sources to generate the active nitrogen species for growth, has been used for III-Nitride compounds doped either n-type with silicon or p-type with magnesium. Blue and violet light emitting diode (LED) test structures were fabricated. These vertical devices required a relatively high forward current and exhibited high leakage currents. This behavior was attributed to parallel shorting mechanisms along the dislocations in MBE grown layers. For comparison, similar devices were fabricated using a single wafer vertical flow MOVPE reactor and ammonia as the active nitrogen species. MOVPE grown blue LEDs exhibited excellent forward device characteristics and a high reverse breakdown voltage. We feel that the excess hydrogen, which is present on the GaN surface due to the dissociation of ammonia in MOVPE, acts to passivate the dislocations and eliminate parallel shorting for vertical device structures. These findings support the widespread acceptance of MOVPE, rather than MBE, as the epitaxial growth technique of choice for III-V nitride materials used in vertical transport bipolar devices for optoelectronic applications.}, number={G5.10}, journal={MRS Internet Journal of Nitride Semiconductor Research}, author={Johnson, M. A. L. and Yu, Z. H. and Brown, J. D. and Koeck, F. A. and El-Masry, N. A. and Kong, H. S. and Edmond, J. A. and Cook, J. W. and Schetzina, J. F.}, year={1999} }
 @article{muth_brown_johnson_yu_kolbas_cook_schetzina_1999, title={Absorption coefficient and refractive index of GaN, AlN and AlGaN alloys}, volume={4S1}, number={G5.2}, journal={MRS Internet Journal of Nitride Semiconductor Research}, author={Muth, J. F. and Brown, J. D. and Johnson, M. A. L. and Yu, Z. H. and Kolbas, R. M. and Cook, J. W. and Schetzina, J. F.}, year={1999} }
 @article{yu_johnson_brown_el-masry_muth_cook_schetzina_haberern_kong_edmond_1999, title={Epitaxial lateral overgrowth of GaN on SiC and sapphire substrates}, volume={4S1}, DOI={10.1557/s1092578300002878}, abstractNote={The epitaxial lateral overgrowth (ELO) process for GaN has been studied using SiC and sapphire substrates. Both MBE and MOVPE growth processes were employed in the study. The use of SiO 2 versus SiN x insulator stripes was investigated using window/stripe widths ranging from 20 μm/4 μm to 3 μm/15 μm. GaN film depositions were completed at temperatures ranging from 800 °C to 1120 °C. Characterization experiments included RHEED, TEM, SEM and cathodolumenescence studies. The MBE growth experiments produced polycrystalline GaN over the insulator stripes even at deposition temperatures as high as 990 °C. In contrast, MOVPE growth produced single-crystal GaN stripes with no observable threading dislocations.}, number={G4.3}, journal={MRS Internet Journal of Nitride Semiconductor Research}, author={Yu, Z. H. and Johnson, M. A. L. and Brown, J. D. and El-Masry, N. A. and Muth, J. F. and Cook, J. W. and Schetzina, J. F. and Haberern, K. W. and Kong, H. S. and Edmond, J. S.}, year={1999} }
 @article{johnson_yu_brown_el-masry_cook_schetzina_1999, title={Scanning electron microscopy and cathodoluminescence study of the epitaxial lateral overgrowth (ELO) process for gallium nitride}, volume={28}, ISSN={["0361-5235"]}, DOI={10.1007/s11664-999-0030-1}, number={3}, journal={JOURNAL OF ELECTRONIC MATERIALS}, author={Johnson, MAL and Yu, ZH and Brown, JD and El-Masry, NA and Cook, JW and Schetzina, JF}, year={1999}, month={Mar}, pages={295–300} }
 @article{johnson_brown_el-masry_cook_schetzina_kong_edmond_1998, title={Molecular beam epitaxy growth and properties of GaN, InGaN, and GaN/InGaN quantum well structures}, volume={16}, ISSN={["1071-1023"]}, DOI={10.1116/1.590000}, abstractNote={Growth of III–V nitrides by molecular beam epitaxy (MBE) was studied using rf nitrogen plasma sources. Plasma sources from three different vendors have been tested. All three of the sources have been used to grow high quality GaN. However, the EPI rf source produces an optical emission spectrum that is very rich in the active nitrogen species of 1st-positive excited nitrogen molecules and nitrogen atoms. GaN growth rates at 800 °C of 1 μm/h have been achieved using this source. The MBE-grown GaN films are deposited homoepitaxially on high quality metalorganic vapor phase epitaxy-grown GaN/SiC substrates. With the growth conditions for high quality undoped GaN as a base line, a detailed study of Mg doping for p-type GaN was performed. An acceptor incorporation of 2×1019 cm−3 was measured by both capacitance–voltage and secondary ion mass spectroscopy for a doping source temperature of 290 °C. However, a faceted three-dimensional growth mode was observed by reflection high energy electron diffraction during...}, number={3}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B}, author={Johnson, MAL and Brown, JD and El-Masry, NA and Cook, JW and Schetzina, JF and Kong, HS and Edmond, JA}, year={1998}, pages={1282–1285} }
 @article{yu_johnson_brown_el-masry_cook_schetzina_1998, title={Study of the epitaxial-lateral-overgrowth (ELO) process for GaN on sapphire}, volume={195}, ISSN={["0022-0248"]}, DOI={10.1016/S0022-0248(98)00638-1}, abstractNote={Growth of GaN by MOVPE on mismatched substrates such as sapphire and SiC produces a columnar material consisting of many hexagonal grains ∼0.2–1.0 μm in diameter. However, the epitaxial–lateral-overgrowth (ELO) process for GaN creates a new material – single-crystal GaN. We have studied the ELO process using a MOVPE reactor featuring vertical gas flows and fast substrate rotation to synthesize GaN ELO samples. Characterization experiments consisted of plan-view scanning electron microscopy and vertical-cross-section transmission electron microscopy studies, which disclosed a large reduction in dislocations in the ELO regions of the GaN samples. Panchromatic and monochromatic cathodoluminescence images and spectra were employed to study the spatial variation of the optical properties of the GaN ELO samples.}, number={1-4}, journal={JOURNAL OF CRYSTAL GROWTH}, author={Yu, ZH and Johnson, MAL and Brown, JD and El-Masry, NA and Cook, JW and Schetzina, JF}, year={1998}, month={Dec}, pages={333–339} }
 @article{johnson_hughes_rowland_cook_schetzina_leonard_kong_edmond_zavada_1997, title={Growth of GaN, InGaN, and AlGaN films and quantum well structures by molecular beam epitaxy}, volume={175}, ISSN={["1873-5002"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0001866991&partnerID=MN8TOARS}, DOI={10.1016/S0022-0248(96)01019-6}, abstractNote={GaN, AlGaN and InGaN films have been grown by molecular beam epitaxy (MBE) using RF plasma sources for the generation of active nitrogen. These films have been deposited homoepitaxially onto GaNSiC substrates and heteroepitaxially onto LiGaO2 substrates. LiGaO2 is an ordered and closely-lattice-matched orthorhombic variant of the wurtzite crystal structure of GaN. A low-temperature AlN buffer layer is necessary in order to nucleate GaN on LiGaO2. Thick GaN and AlGaN layers may then be grown once deposition is initiated. InGaN has been grown by MBE at mole fractions of up to 20% as a quantum well between GaN cladding layers. The indium containing structures were deposited onto GaNSiC substrates to focus the development effort on the InGaN growth process rather than on heteroepitaxial nucleation. A modulated beam technique, with alternating short periods of (In, Ga)N and (Ga)N, was used to grow high-quality InGaN. The modulated beam limits the nucleation of metal droplets on the growth surface, which form due to thermodynamic limitations. A narrow PL dominated by band edge luminescence at 421 nm results from this growth technique. Growth of GaN at high temperatures is also reported.}, note={Place: Malibu, CA, USA Publisher: Elsevier Sci B.V.}, number={PART 1}, journal={JOURNAL OF CRYSTAL GROWTH}, author={Johnson, MAL and Hughes, WC and Rowland, WH and Cook, JW and Schetzina, JF and Leonard, M and Kong, HS and Edmond, JA and Zavada, J}, year={1997}, month={May}, pages={72–78} }
 @article{johnson_fujita_rowland_bowers_hughes_he_elmasry_cook_schetzina_ren_et al._1997, title={MBE growth and properties of GaN on GaN/SiC substrates}, volume={41}, ISSN={["0038-1101"]}, DOI={10.1016/S0038-1101(96)00169-4}, abstractNote={Abstract Growth of III–V nitrides by molecular beam epitaxy (MBE) is being studied at NCSU using an r.f. nitrogen plasma source. GaN SiC substrates consisting of ∼ 3 μm thick GaN buffer layers grown on 6HSiC wafers by MOVPE at Cree Research Inc. are being used as substrates in the MBE film growth experiments. The MBE-grown GaN films exhibit excellent structural and optical properties—comparable to the best GaN films grown by MOVPE—as determined from photoluminescence, X-ray diffraction, and vertical-cross-section TEM micrographs. Mg and Si have been used as dopants for p -type and n -type layers, respectively. Al x Ga 1 − x N films ( x ∼ 0.06-0.08) and Al x Ga 1 − x N GaN multi-quantum-well structures have been grown which display good optical properties. Light-emitting diodes based on double-heterostructures of Al x Ga 1 − x N GaN which emit violet light at ∼400 nm have also been demonstrated. Growth of GaN on LiGaO 2 substrates is also reported for comparison.}, number={2}, journal={SOLID-STATE ELECTRONICS}, author={Johnson, MAL and Fujita, S and Rowland, WH and Bowers, KA and Hughes, WC and He, YW and ElMasry, NA and Cook, JW and Schetzina, JF and Ren, J and et al.}, year={1997}, month={Feb}, pages={213–218} }
 @article{hughes_boney_johnson_cook_schetzina_1997, title={Surface preparation of ZnSe substrates for MBE growth of II-VI light emitters}, volume={175}, ISSN={["0022-0248"]}, DOI={10.1016/S0022-0248(96)01022-6}, abstractNote={Abstract This paper describes substrate surface preparation techniques used in the development II–VI light emitting diode and laser diode structures on high-quality, bulk ZnSe substrates supplied by Eagle-Picher Industries. The use of ZnSe substrates eliminates many of the problems associated with lattice mismatch in heteroepitaxy of II–VI light emitters on GaAs substrates. However, defects still form during nucleation of an epitaxial layer on ZnSe substrates because of surface roughness, contamination, and defects. We have employed a variety of wet chemical etches, vacuum anneals, plasma treatments, and characterization techniques such as RHEED, Auger electron spectroscopy, and SEM studies to improve the ZnSe substrate surface prior to MBE film growth. A combination of hydrogen plasma exposure and annealing was found to be the most effective way to remove contaminants from ZnSe substrates but less than optimum homoepitaxial quality showed that the surface preparation is more complex than simply cleaning the polished surface. Since polishing can leave residual damage in the form of near-surface defects, the top layer of these substrates was removed by reactive ion etching with BCl 3 . Parameters were chosen such that this etch was homogeneous and smoothed the ZnSe surface. Etch pit density measurements revealed that the polish-induced damage to ZnSe extended up to about 5 μm deep. A dramatic improvement in the characteristics of blue/green light emitting devices was observed for devices grown on ZnSe substrates from which this damaged layer had been removed. This surface preparation procedure has led to the brightest and longest lasting II–VI green LEDs made in the world today.}, journal={JOURNAL OF CRYSTAL GROWTH}, author={Hughes, WC and Boney, C and Johnson, MAL and Cook, JW and Schetzina, JF}, year={1997}, month={May}, pages={546–551} }