@misc{piner_rajagopal_roberts_linthicum_2008, title={Gallium nitride material structures including substrates and methods associated with the same}, volume={7,365,374}, number={2008 Apr. 29}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Piner, E. L. and Rajagopal, P. and Roberts, J. C. and Linthicum, K. J.}, year={2008} }
 @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_2008, title={Stimulated emission and lasing from an Al0.13Ga0.87N/GaN double heterostructure grown on a silicon substrate}, volume={92}, number={2}, 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={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{moody_barletta_el-masry_roberts_aumer_leboeuf_bedair_2002, title={Effect of H-2 on nitrogen incorporation in the metalorganic chemical vapor deposition of GaAs1-yNy (0 <= y <= 0.08)}, volume={80}, ISSN={["0003-6951"]}, DOI={10.1063/1.1464225}, abstractNote={The effect of hydrogen on the incorporation of nitrogen in GaAs1−yNy grown by metalorganic chemical vapor deposition (MOCVD) is reported. Nitrogen content as high as y=0.081 has been achieved when the use of H2 is completely avoided in the MOCVD growth of GaAs1−yNy. When H2 is added to the growth ambient, the value of y in GaAs1−yNy decreases as the relative percent of H2 in the carrier gas increases. We will report on the properties of these GaAsN films and discuss the nature of the effect that H2 has on modulating the N content in these films.}, number={14}, journal={APPLIED PHYSICS LETTERS}, author={Moody, BF and Barletta, PT and El-Masry, NA and Roberts, JC and Aumer, ME and LeBoeuf, SF and Bedair, SM}, year={2002}, month={Apr}, pages={2475–2477} }
 @misc{roberts_parker_muth_leboeuf_aumer_bedair_reed_2002, title={Ultraviolet-visible metal-semiconductor-metal photodetectors fabricated from InxGa1-xN (0 <= x <= 0.13)}, volume={31}, number={1}, journal={Journal of Electronic Materials}, author={Roberts, J. C. and Parker, C. A. and Muth, J. F. and Leboeuf, S. F. and Aumer, M. E. and Bedair, S. M. and Reed, M. J.}, year={2002}, month={Jan}, pages={L1–6} }
 @article{liliental-weber_benamara_washburn_domagala_bak-misiuk_piner_roberts_bedair_2001, title={Relaxation of InGaN thin layers observed by x-ray and transmission electron microscopy studies}, volume={30}, ISSN={["0361-5235"]}, DOI={10.1007/s11664-001-0056-5}, number={4}, journal={JOURNAL OF ELECTRONIC MATERIALS}, author={Liliental-Weber, Z and Benamara, M and Washburn, J and Domagala, JZ and Bak-Misiuk, J and Piner, EL and Roberts, JC and Bedair, SM}, year={2001}, month={Apr}, pages={439–444} }
 @article{reed_el-masry_stadelmaier_ritums_reed_parker_roberts_bedair_2001, title={Room temperature ferromagnetic properties of (Ga, Mn)N}, volume={79}, ISSN={["1077-3118"]}, DOI={10.1063/1.1419231}, abstractNote={Dilute magnetic semiconductor GaN with a Curie temperature above room temperature has been achieved by manganese doping. By varying the growth and annealing conditions of Mn-doped GaN we have identified Curie temperatures in the range of 228–370 K. These Mn-doped GaN films have ferromagnetic behavior with hysteresis curves showing a coercivity of 100–500 Oe. Structure characterization by x-ray diffraction and transmission electron microscopy indicated that the ferromagnetic properties are not a result of secondary magnetic phases.}, number={21}, journal={APPLIED PHYSICS LETTERS}, author={Reed, ML and El-Masry, NA and Stadelmaier, HH and Ritums, MK and Reed, MJ and Parker, CA and Roberts, JC and Bedair, SM}, year={2001}, month={Nov}, pages={3473–3475} }
 @article{el-masry_behbehani_leboeuf_aumer_roberts_bedair_2001, title={Self-assembled AlInGaN quaternary superlattice structures}, volume={79}, ISSN={["0003-6951"]}, DOI={10.1063/1.1400763}, abstractNote={When an AlInGaN quaternary alloy is grown by metalorganic chemical-vapor deposition under certain growth conditions, a self-assembled superlattice structure is obtained. The superlattice structure is made of quaternary layers with different AIN and InN compositions. Transmission electron microscopy data show that the superlattice periodicity is regular with an individual layer thickness that depends on the growth conditions. Secondary ion mass spectrometry measurements show that the layers’ composition alternate between high-AIN and InN content and low-AlN and-InN content, while the in-plane lattice constant remains constant for both layers. A model is presented as a preliminary effort to explain these results.}, number={11}, journal={APPLIED PHYSICS LETTERS}, author={El-Masry, NA and Behbehani, MK and LeBoeuf, SF and Aumer, ME and Roberts, JC and Bedair, SM}, year={2001}, month={Sep}, pages={1616–1618} }
 @article{reed_el-masry_parker_roberts_bedair_2000, title={Critical layer thickness determination of GaN/InGaN/GaN double heterostructures}, volume={77}, DOI={10.1063/1.1334361}, abstractNote={We report on the critical layer thickness of GaN/InxGa1−xN/GaN double heterostructures in the composition range 0<x<0.16. The evolution of the photoluminescence spectra and the electrical properties of the InxGa1−xN well were monitored as its thickness was increased for a given % InN. Due to compressive stress and possible quantum-size effects, the emission energy from thin InGaN wells is blueshifted relative to thicker wells of a given % InN. The transition from the blueshifted emission of strained InGaN to redshifted emission of relaxed InGaN is also accompanied by dramatic changes in film conductivity and mobility. The thickness at which the onset of relaxation occurs is deemed the critical layer thickness of the InxGa1−xN film.}, number={25}, journal={Applied Physics Letters}, author={Reed, M. J. and El-Masry, N. A. and Parker, C. A. and Roberts, J. C. and Bedair, S. M.}, year={2000}, pages={4121–4123} }
 @article{hunter_reed_el-masry_roberts_bedair_2000, title={Epitaxial Y2O3 films grown on Si(111) by pulsed-laser ablation}, volume={76}, ISSN={["0003-6951"]}, DOI={10.1063/1.126217}, abstractNote={Y2O3 has a relatively high dielectric constant (13–17) leading to several potential applications. In this work, pulsed-laser deposition was used to grow epitaxial Y2O3 films on Si(111) substrates. Structural characterization indicated two-dimensional growth without the formation of an amorphous interfacial layer. Annealing in either Ar or O2 was found to induce an O2 diffusion reaction resulting in the formation of two interfacial amorphous layers. Electrical characterization by capacitance–voltage and current–voltage indicated that the as-grown samples were poor insulating films. Annealing the samples improved the electrical performance by lowering leakage currents and exhibiting inversion during capacitance–voltage testing. This epitaxial growth points toward the possibility of the heteroepitaxial growth of silicon on insulator device structures.}, number={14}, journal={APPLIED PHYSICS LETTERS}, author={Hunter, ME and Reed, MJ and El-Masry, NA and Roberts, JC and Bedair, SM}, year={2000}, month={Apr}, pages={1935–1937} }
 @article{reed_liu_roberts_stadelmaier_bedair_el-masry_2000, title={The planar Hall effect in MnSb films and MnSb-based multilayer structures grown on (111)B GaAs}, volume={218}, ISSN={["0304-8853"]}, DOI={10.1016/S0304-8853(00)00403-0}, abstractNote={We report on the planar Hall effect properties of ferromagnetic MnSb films in ferromagnetic/nonmagnetic multilayer structures. We demonstrate an enhancement of the relative planar Hall resistivity when MnSb is used in multilayer structures. In single-layer MnSb films, the relative planar Hall resistivity is ∼2.5%, while the multilayer structures demonstrate up to ∼41% change. The following structures were prepared by pulsed laser deposition and grown on (1 1 1)B GaAs: epitaxial and polycrystalline MnSb thin films, MnSb/Bi multilayers and Mn/Sb/Mn/Bi multilayers. The multilayer structures also demonstrate temperature dependence, as the relative resistivity decreases to ∼30% when the temperature decreases to 100 K.}, number={2-3}, journal={JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS}, author={Reed, ML and Liu, SX and Roberts, JC and Stadelmaier, HH and Bedair, SM and El-Masry, NA}, year={2000}, month={Aug}, pages={177–181} }
 @article{parker_roberts_bedair_reed_liu_el-masry_1999, title={Determination of the critical layer thickness in the InGaN/GaN heterostructures}, volume={75}, ISSN={["0003-6951"]}, DOI={10.1063/1.125146}, abstractNote={We present an approach to determine the critical layer thickness in the InxGa1−xN/GaN heterostructure based on the observed change in the photoluminescence emission as the InxGa1−xN film thickness increases. From the photoluminescence data, we identify the critical layer thickness as the thickness where a transition occurs from the strained to unstrained condition, which is accompanied by the appearance of deep level emission and a drop in band edge photoluminescence intensity. The optical data that indicate the onset of critical layer thickness, was also confirmed by the changes in InxGa1−xN surface morphology with thickness, and is consistent with x-ray diffraction measurements.}, number={18}, journal={APPLIED PHYSICS LETTERS}, author={Parker, CA and Roberts, JC and Bedair, SM and Reed, MJ and Liu, SX and El-Masry, NA}, year={1999}, month={Nov}, pages={2776–2778} }
 @article{robins_paul_parker_roberts_bedair_piner_el-masry_1999, title={Optical absorption, Raman, and photoluminescence excitation spectroscopy of inhomogeneous InGaN films}, volume={4S1}, DOI={10.1557/s1092578300002490}, abstractNote={InGa l-x N films with x=0.06 to x=0.49 were characterized by optical transmittance, Raman, and photoluminescence excitation spectroscopies. Previous microstructural characterizations detected phase separation only in films with x>0.2. The transmittance data suggest that compositional inhomogeneity is also present in the lower-x films (x 0.2. The composition dependence of the Raman spectra, from x=0.28 to x=0.49, is consistent with an increase in the size of the phase-separated regions with increasing x.}, number={G3.22}, journal={MRS Internet Journal of Nitride Semiconductor Research}, author={Robins, L. H. and Paul, A. J. and Parker, C. A. and Roberts, J. C. and Bedair, S. M. and Piner, E. L. and El-Masry, N. A.}, year={1999} }
 @article{parker_roberts_bedair_reed_liu_el-masry_robins_1999, title={Optical band gap dependence on composition and thickness of InxGa1-xN (0 < x < 0.25) grown on GaN}, volume={75}, ISSN={["1077-3118"]}, DOI={10.1063/1.125079}, abstractNote={Band gap measurements have been carried out in strained and relaxed InxGa1−xN epilayers with x<0.25. Values of x were determined from x-ray diffraction of relaxed films. The lowest energy absorption threshold, measured by transmittance, was found to occur at the same energy as the peak of the photoluminescence spectrum. Bowing parameters for both strained and relaxed films were determined to be 3.42 and 4.11 eV, respectively. The dependence of the band gap shift, ΔEg, on strain is presented.}, number={17}, journal={APPLIED PHYSICS LETTERS}, author={Parker, CA and Roberts, JC and Bedair, SM and Reed, MJ and Liu, SX and El-Masry, NA and Robins, LH}, year={1999}, month={Oct}, pages={2566–2568} }
 @misc{mcintosh_bedair_el-masry_roberts_1998, title={Methods of forming indium gallium nitride or aluminum indium gallium nitride using controlled hydrogen gas flow}, volume={5,851,905}, number={1998 Dec. 22}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={McIntosh, F. G. and Bedair, S. M. and El-Masry, N. A. and Roberts, J. C.}, year={1998}, month={Dec} }
 @article{piner_behbehani_elmasry_mcintosh_roberts_boutros_bedair_1997, title={Effect of hydrogen on the indium incorporation in InGaN epitaxial films}, volume={70}, ISSN={["0003-6951"]}, DOI={10.1063/1.118181}, abstractNote={The InN percent in metalorganic chemical vapor deposition (MOCVD) and atomic layer epitaxy (ALE) grown InGaN was found to be significantly influenced by the amount of hydrogen flowing into the reactor. The temperature ranges for this study are 710–780 °C for MOCVD, and 650–700 °C for ALE. For a given set of growth conditions, an increase of up to 25% InN in InGaN, as determined by x-ray diffraction, can be achieved by reducing the hydrogen flow from 100 to 0 sccm. Additionally, the hydrogen produced from the decomposition of ammonia does not seem to change the InN percent in the films, indicating that the ammonia decomposition rate is less than 0.1%. The phenomenon of having hydrogen control the indium incorporation was not reported in the growth of any other III–V compound previously studied.}, number={4}, journal={APPLIED PHYSICS LETTERS}, author={Piner, EL and Behbehani, MK and ElMasry, NA and McIntosh, FG and Roberts, JC and Boutros, KS and Bedair, SM}, year={1997}, month={Jan}, pages={461–463} }
 @article{mcintosh_piner_roberts_behbehani_aumer_elmasry_bedair_1997, title={Epitaxial deposition of GaInN and InN using the rotating susceptor ALE system}, volume={112}, ISSN={["0169-4332"]}, DOI={10.1016/S0169-4332(96)00992-0}, abstractNote={The growth of GaInN ternary alloys has been investigated using atomic layer epitaxy. Single crystal films have been deposited at 100 Torr in the 600°C to 700°C temperature range using the rotating susceptor approach. The InN percentage in the deposited films were found to depend on more than just the gas phase In/Ga ratio. In addition to the relative indium to gallium composition of the precursor gases, the indium incorporation was also found to depend on the absolute partial pressures of the reactant gases. The indium incorporation increases with decreasing growth temperatures, and may reach a temperature dependent saturation limit for a given set of growth conditions. Optimization of the ALE growth process has resulted in single crystal films exhibiting band edge room temperature photoluminescence for InN percentages of up to 27% in the GaInN ternary films. In addition, single crystal indium nitride has been grown using the ALE technique at 480°C.}, journal={APPLIED SURFACE SCIENCE}, author={McIntosh, FG and Piner, EL and Roberts, JC and Behbehani, MK and Aumer, ME and ElMasry, NA and Bedair, SM}, year={1997}, month={Mar}, pages={98–101} }
 @article{bedair_mcintosh_roberts_piner_boutros_elmasry_1997, title={Growth and characterization of In-based nitride compounds}, volume={178}, ISSN={["0022-0248"]}, DOI={10.1016/S0022-0248(97)00069-9}, abstractNote={Development of In-based nitride compounds is lagging behind the corresponding Al- and Ga-based compounds. Potential problems facing the growth of Inx Ga1 − x N films and their double heterostructures will be outlined. A tentative model which describes the reaction pathways taking place during the growth of these In-based nitride compounds is presented and is used to explain both our ALE and MOCVD results. In addition, growth parameters leading to the achievement of high values of x, reduction of In metal incorporation and improvement of both the structural and optical properties of InGaN, AlGaInN and InN will be discussed. Properties of AlGaN/InGaN/AlGaN and AlGaInN/InGaN/AlGaInN double heterostructures will be presented, with emission wavelengths in the 400–550 nm range.}, number={1-2}, journal={JOURNAL OF CRYSTAL GROWTH}, author={Bedair, SM and McIntosh, FG and Roberts, JC and Piner, EL and Boutros, KS and ElMasry, NA}, year={1997}, month={Jun}, pages={32–44} }
 @article{piner_behbehani_elmasry_roberts_mcintosh_bedair_1997, title={Impurity dependence on hydrogen and ammonia flow rates in InGaN bulk films}, volume={71}, ISSN={["0003-6951"]}, DOI={10.1063/1.119775}, abstractNote={H, C, and O impurity concentrations in metalorganic chemical vapor deposition grown InGaN were found to be dependent on the hydrogen and NH3 flow rates. By increasing the hydrogen flow rate from 0 to 100 sccm, a decrease of greater than two orders of magnitude in the C and O impurity levels and one order of magnitude in the H impurity level was observed. Increasing the NH3 flow rate from 1 to 5 slm results in a decrease in the C concentration and an increase in the H and O concentrations indicating that high purity NH3 (99.999%) can be a significant source of O contamination. Additional studies show that when the InN percent in the InGaN films increases, the impurity concentrations increase regardless of changes in the growth conditions. The InGaN films were grown from 710 to 780 °C and the impurity concentrations were characterized by secondary ion mass spectrometry.}, number={14}, journal={APPLIED PHYSICS LETTERS}, author={Piner, EL and Behbehani, MK and ElMasry, NA and Roberts, JC and McIntosh, FG and Bedair, SM}, year={1997}, month={Oct}, pages={2023–2025} }
 @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} }
 @article{zeng_smith_lin_jiang_roberts_piner_mcintosh_1997, title={Optical transitions in InGaN/AlGaN single quantum wells}, volume={15}, number={4}, journal={Journal of Vacuum Science & Technology. B, Microelectronics and Nanometer Structures}, author={Zeng, K. C. and Smith, M. and Lin, J. Y. and Jiang, H. X. and Roberts, John C. and Piner, E. L. and McIntosh, F. G.}, year={1997}, pages={1139–1143} }
 @misc{mcintosh_bedair_el-masry_roberts_1997, title={Stacked quantum well aluminum indium gallium nitride light emitting diodes}, volume={5,684,309}, number={1997 Nov. 4}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={McIntosh, F. G. and Bedair, S. M. and El-Masry, N. A. and Roberts, J. C.}, year={1997}, month={Nov} }