@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} }