TY - RPRT T1 - Angular selective window systems: Assessment of technical potential for energy saving Y1 - 2014/01// SP - 36 A1 - Luis L. Fernandes A1 - Eleanor S. Lee A1 - Andrew McNeil A1 - Jacob C. Jonsson A1 - Thierry Stephane Nouidui A1 - Xiufeng Pang A1 - Sabine Hoffmann KW - angular selective systems KW - Building energy-efficiency KW - daylighting KW - Shading Systems KW - windows AB - Static angular selective shading systems block or filter direct sunlight and admit daylight within a specific range of incident solar angles. They can potentially deliver energy efficient performance within the typical 4.6-m (15-ft) deep perimeter zone of buildings when tailored to a specific façade orientation and latitude. The objective of this study is to quantify the technical potential of these systems to reduce energy use and peak demand in commercial buildings, specifically: a) achieve 30-50% reductions in perimeter zone energy use vs. ASHRAE 90.1-2004, b) constrain peak window loads to less than 43 W/m2-floor (4 W/ft2-floor), and c) to the extent possible, admit useful daylight in the perimeter zone without exceeding the peak solar load constraint. Three distinctly different commercial shading systems were evaluated: a micro-perforated screen, a tubular shading structure (double- and triple-paned configurations), and an expanded metal mesh. This evaluation was performed mainly through computer simulation for a multitude of scenarios, including multiple climates (Chicago, Illinois and Houston, Texas), window-to-wall ratios (0.15-0.60), building codes (ASHRAE 90.1-2004 and 2010) and lighting control configurations (with and without daylighting controls). Angular selective shading systems are optically complex and cannot be modeled accurately using conventional simulation tools, prompting the development of unique versions of the EnergyPlus, Radiance and Window simulation tools. Results show significant potential reductions in perimeter zone energy use, with the best commercially-available system reaching 28% and 47% savings, relative to ASHRAE 90.1- 2004 and respectively without and with daylighting controls, on south facades in Chicago with WWR=0.45, while constraining peak window heat gains to under 43 W/m2-floor, and enabling significant savings from daylighting controls. Results suggest that it is possible that existing systems can be improved to more consistently achieve 30-50% energy savings. Level of angular selectivity, spectral selectivity of low-e coatings and thermal conductance of the angle-selective layer were identified as critical factors for the performance of angular selective systems. Static, angular selective shading systems offer a potentially low-cost option to significantly reduce window heat gains and control glare from visibility of the sun orb, while permitting the admission of useful daylight and access to views to the outdoors. This type of system shows significant potential to contribute towards net-zero energy goals in both new and retrofit construction. N1 -

Submitted to Energy and Buildings, May 27, 2014

U2 - LBNL-187060 ER - TY - JOUR T1 - Drifting Ionization Zone in DC Magnetron Sputtering Discharges at Very Low Currents JF - IEEE Transactions on Plasma Science Y1 - 2014/10// SP - 2578 EP - 2579 A1 - André Anders A1 - Pavel A Ni A1 - Joakim Andersson AB - Discharges with crossed electric and magnetic fields are known to develop instabilities that are crucial in the transport of charged particles. Sputtering magnetrons are no exception. While most recent studies focused on traveling ionization zones in high power impulse magnetron sputtering, we show here fast camera images of magnetron discharges at very low current. A single drifting ionization zone is always present, even down to the threshold current of about 10 mA. VL - 42 IS - 10 JO - IEEE Trans. Plasma Sci. DO - 10.1109/TPS.2014.2334601 ER - TY - RPRT T1 - Automated Production of Optimization-Based Control Logics for Dynamic Façade Systems, with Experimental Application to Two-Zone External Venetian Blinds Y1 - 2013/09// A1 - Brian E. Coffey A1 - Andrew McNeil A1 - Thierry Stephane Nouidui A1 - Eleanor S. Lee ER - TY - JOUR T1 - Drifting potential humps in ionization zones: The “propeller blades” of high power impulse magnetron sputtering JF - Applied Physics Letters Y1 - 2013/10// SP - 144103 A1 - André Anders A1 - Matjaž Panjan A1 - Robert Franz A1 - Joakim Andersson A1 - Pavel A. Ni KW - Electric fields KW - ionization KW - plasma ionization KW - sputter deposition KW - sputtering AB - Ion energy distribution functions measured for high power impulse magnetron sputtering show features, such as a broad peak at several 10 eV with an extended tail, as well as asymmetry with respect to E × B, where E and B are the local electric and magnetic field vectors, respectively. Here it is proposed that those features are due to the formation of a potential hump of several 10 V in each of the traveling ionization zones. Potential hump formation is associated with a negative-positive-negative space charge that naturally forms in ionization zones driven by energetic drifting electrons. VL - 103 IS - 14 JO - Appl. Phys. Lett. DO - 10.1063/1.4823827 ER - TY - JOUR T1 - Spectroscopic imaging of self-organization in high power impulse magnetron sputtering plasmas JF - Applied Physics Letters Y1 - 2013/07// SP - 054104 A1 - Joakim Andersson A1 - Pavel A Ni A1 - André Anders KW - Aluminium KW - ionization KW - Ionizing radiation KW - plasma ionization KW - visible spectra AB - Excitation and ionization conditions in traveling ionization zones of high power impulse magnetron sputtering plasmas were investigated using fast camera imaging through interference filters. The images, taken in end-on and side-on views using light of selected gas and target atom and ion spectral lines, suggest that ionization zones are regions of enhanced densities of electrons, and excited atoms and ions. Excited atoms and ions of the target material (Al) are strongly concentrated near the target surface. Images from the highest excitation energies exhibit the most localized regions, suggesting localized Ohmic heating consistent with double layer formation. VL - 103 IS - 5 JO - Appl. Phys. Lett. DO - 10.1063/1.4817257 ER - TY - RPRT T1 - Development of a simulation-based controls framework for implementation of controls algorithms for complex fenestration systems Y1 - 2012/09// SP - 15 A1 - Thierry Stephane Nouidui A1 - Andrew McNeil A1 - Eleanor S. Lee AB - Effectively controlled dynamic windows can substantially reduce the energy consumption of buildings. Unfortunately, modular and extensible frameworks for testing and evaluating window system control algorithms that include the effects of thermal mass are missing in the research community.This paper describes a modular and extensible simulation-based framework that uses different simulation tools such as EnergyPlus, Modelica, Radiance, and the Building Controls Virtual Test Bed (BCVTB) to develop and evaluate the performance of integrated façade control strategies. We present a simulation framework and a proof-of concept application using the framework to control a venetian blind in a physical test cell in order to reduce its zone thermal load based on solar inputs and internal gains measured at the test cell. ER - TY - JOUR T1 - Drifting localization of ionization runaway: Unraveling the nature of anomalous transport in high power impulse magnetron sputtering JF - Journal of Applied Physics Y1 - 2012/03// SP - 053304 A1 - André Anders A1 - Pavel A Ni A1 - Albert Rauch KW - Cameras KW - ionization KW - Magnetic fields KW - Plasma density KW - plasma ionization AB - The plasma over a magnetron’s erosion “racetrack” is not azimuthally uniform but concentrated in distinct dense ionization zones which move in the E x B direction with about 10% of the electron E x B/B2 drift velocity. The ionization zones are investigated with a gated camera working in concert with a streak camera for Al, Nb, Cu, and W targets in Ar or Kr background gas. It is found that each ionization zone has a high plasma density edge, which is the origin of a plasma-generating electron jet leaving the target zone. Each region of strong azimuthal plasma density gradient generates an azimuthal electric field, which promotes the escape of magnetized electrons and the formation of electron jets and plasma flares. The phenomena are proposed to be caused by an ionization instability where each dense plasma zone exhibits a high stopping power for drifting high energy electrons, thereby enhancing itself. VL - 111 IS - 5 JO - J. Appl. Phys. DO - 10.1063/1.3692978 ER - TY - RPRT T1 - Validation of the Window Model of the Modelica Buildings Library Y1 - 2012/07// A1 - Thierry Stephane Nouidui A1 - Michael Wetter A1 - Wangda Zuo AB - This paper describes the validation of the window model of the free open-source Modelica Buildings library. This paper starts by describing the physical modeling assumptions of the window model. The window model can be used to calculate the thermal and angular properties of glazing systems. It can also be used for steady-state simulation of heat transfer mechanism in glazing systems. We present simulation results obtained by comparing the window model with WINDOW 6 the well established simulation tool for steady-state heat transfer in glazing systems. We also present results obtained by comparing the window model with measurements carried out in a test cell at the Lawrence Berkeley National Laboratory. U2 - LBNL-5735E ER - TY - RPRT T1 - Modeling solar heat gains of complex fenestration systems using bidirectional scattering distribution functions Y1 - 2011/09// A1 - Thierry Stephane Nouidui A1 - Andrew McNeil A1 - Christian Kohler A1 - Brian E. Coffey A1 - Eleanor S. Lee ER - TY - JOUR T1 - Light-scattering properties of a Venetian blind slat used for daylighting applications JF - Solar Energy Y1 - 2010/12// SP - 2103 EP - 2111 A1 - Annica M. Nilsson A1 - Jacob C. Jonsson KW - ABg-model KW - BSDF KW - Raytracing KW - Venetian blinds AB - The low cost, simplicity, and aesthetic appearance of external and internal shading devices, make them commonly used for daylighting and glare-control applications. Shading devices, such as Venetian blinds, screens, and roller shades, generally exhibit light scattering and/or light redirecting properties. This requires the bi-directional scattering distribution function (BSDF) of the material to be known in order to accurately predict the daylight distribution and energy flow through the fenestration system. Acquiring the complete BSDF is not a straightforward task, and to complete the process it is often required that a model is used to complement the measured data. In this project, a Venetian blind slat with a white top surface and a brushed aluminum bottom surface was optically characterized. A goniophotometer and an integrating sphere spectrophotometer were used to determine the angle resolved and hemispherical reflectance of the sample, respectively. The acquired data were fitted to a scattering model providing one Lambertian and one angle dependent description of the surface properties. These were used in combination with raytracing to obtain the complete BSDFs of the Venetian blind system. VL - 84 IS - 12 JO - Solar Energy DO - 10.1016/j.solener.2010.09.005 ER - TY - JOUR T1 - Supersonic metal plasma impact on a surface: an optical investigation of the pre-surface region JF - Journal of Physics D: Applied Physics Y1 - 2010/04// A1 - Pavel A Ni A1 - André Anders KW - cathodic arc plasma KW - ions KW - neutrals KW - optical emission spectroscopy KW - plasma-wall interaction AB - Aluminum plasma, produced in high vacuum by a pulsed, filtered cathodic arc plasma source, was directed onto a wall where if formed a coating. The accompanying "optical flare" known from the literature was visually observed, photographed, and spectroscopically investigated with appropriately high temporal (1 μs) and spatial (100 μm) resolution. Consistent with other observations using different techniques, it was found that the impact of the fully ionized plasma produces metal neutrals as well as desorbed gases, both of which interact with the incoming plasma. Most effectively are charge exchange collisions between doubly charged aluminum and neutral aluminum, which lead to a reduction of the flow of doubly charged before they reach the wall, and a reduction of neutrals as the move away from the surface. Those plasma-wall interactions are relevant for coating processes as well as for interpreting the plasma properties such as ion charge state distributions. VL - 43 IS - 13 U1 -

Windows and Daylighting Group

U2 - LBNL-2982E JO - J. Phys. D: Appl. Phys. DO - 10.1088/0022-3727/43/13/135201 ER - TY - JOUR T1 - Optical characterization of fritted glass for architectural applications JF - Optical Materials Y1 - 2009/ SP - 949 EP - 958 A1 - Jacob C. Jonsson A1 - Michael D. Rubin A1 - Annica M. Nilsson A1 - Andreas Jonsson A1 - Arne Roos KW - BRDF KW - BTDF KW - Fritted glass KW - Integrating sphere KW - light scattering AB - Fritted glass is commonly used as a light diffusing element in modern buildings. Traditionally it has been used for aesthetic purposes but it can also be used for energy savings by incorporating it in novel daylighting systems? To answer such questions the light scattering properties must be properly characterized.This paper contains measurements of different varieties of fritted glass, ranging from the simplest direct-hemispherical measurements to angle-resolved goniometer measurements. Modeling the light scattering to obtain the full bidirectional scattering distribution function (BSDF) extends the measured data, making it useful in simulation programs such as Window 6 and Radiance. Surface profilometry results and SEM micrographs are included to demonstrate the surface properties of the samples studied. VL - 31 IS - 6 JO - Optical Materials DO - 10.1016/j.optmat.2008.10.050 ER - TY - CONF T1 - Energy Efficient Windows in the Southern Residential Windows Market T2 - 2002 ACEEE Summer Study on Energy Efficiency in Buildings Y1 - 2002/08// A1 - Alison Tribble A1 - Kate Offringa A1 - Bill Prindle A1 - Dariush K. Arasteh A1 - Jay Zarnikau A1 - Arlene Stewart A1 - Ken Nittler AB - The greatest potential in the U.S. for cost-effective energy savings from currently available energy efficient residential windows and skylights exists in the southern market. Prindle and Arasteh recently reported that ten southern states could save over 400 million kwh and 233 MW of peak electricity generating capacity annually by adopting the International Energy Conservation Code (IECC) standard of 0.40 (or less) solar heat gain coefficient (SHGC) for new construction (Prindle & Arasteh 2001). In 2000, Anello et al. demonstrated savings of 14.7 percent in reduced cooling load with high-performance windows (Anello et al. 2000). In 2002, Wilcox demonstrated savings of 20 percent while simulation analysis estimates cooling energy savings in the 30 percent range (Wilcox 2002).In the southern market, there is significant opportunity for reducing cooling energy use with low solar gain low-E windows. Yet, the southern market has been slow to embrace this new technology. Market research shows that while low-E products have achieved up to 70 percent of the market share in some colder climates (Jennings, Degens & Curtis 2002), they have gained less than 10 percent of the southern windows market (Prindle & Arasteh 2001).This paper will explore the residential windows market by considering the following: market barriers unique to the southern market; distribution channels in the South; the roles of utilities, codes officials, and other organizations; and other indirect factors that influence this market. This paper will profile current market transformation efforts with case studies of the Florida Windows Initiative, sponsored by the Efficient Windows Collaborative at the Alliance to Save Energy, and the Texas Windows Initiative, sponsored by the American Electric Power Company. Finally, this paper will identify the next steps that will be critical to transforming the southern residential windows market to more efficient window and skylight products. JF - 2002 ACEEE Summer Study on Energy Efficiency in Buildings CY - Pacific Grove, CA U1 -

Windows and Daylighting Group

U2 - LBNL-51425 ER - TY - JOUR T1 - In Situ X-Ray Absorption Spectroscopy Study of Hydrogen Absorption by Nickel-Magnesium Thin Films JF - Physical Review B Y1 - 2003/02// A1 - Baker Farangis A1 - Ponnusamy Nachimuthu A1 - Thomas J. Richardson A1 - Jonathan L. Slack A1 - Rupert C.C. Perera A1 - Eric M. Gullikson A1 - Dennis W. Lindle A1 - Michael D. Rubin AB - Structural and electronic properties of co-sputtered Ni-Mg thin films with varying Ni to Mg ratio were studied by in situ x-ray absorption spectroscopy in the Ni L-edge and Mg K-edge regions. Codeposition of the metals led to increased disorder and decreased coordination around Ni and Mg compared to pure metal films. Exposure of the metallic films to hydrogen resulted in formation of hydrides and increased disorder. The presence of hydrogen as a near neighbor around Mg caused a drastic reduction in the intensities of multiple scattering resonances at higher energies. The optical switching behavior and changes in the x-ray spectra varied with Ni to Mg atomic ratio. Pure Mg films with Pd overlayers were converted to MgH2: The H atoms occupy regular sites as in bulk MgH2. Although optical switching was slow in the absence of Ni, the amount of H2 absorption was large. Incorporation of Ni in Mg films led to an increase in the speed of optical switching but decreased maximum transparency. Significant shifts in the Ni L3 and L2 peaks are consistent with strong interaction with hydrogen in the mixed films. VL - 67 IS - 8 U1 -

Windows and Daylighting Group

U2 - LBNL-51067 JO - Phys. Rev. B DO - 10.1103/PhysRevB.67.085106 ER - TY - CONF T1 - Structural and Electronic Properties of Magnesium-3D Transition Metal Switchable Mirrors T2 - Fifth International Meeting on Electrochromism Y1 - 2002/12// A1 - Baker Farangis A1 - Ponnusamy Nachimuthu A1 - Thomas J. Richardson A1 - Jonathan L. Slack A1 - Bruno K. Meyer A1 - Rupert C.C. Perera A1 - Michael D. Rubin KW - EXAFS KW - Hydrogen storage materials KW - NEXAFS KW - thin films KW - x-ray diffraction AB - We have observed reversible mirror-to-transparent state switching in a variety of mixed metal thin films containing magnesium and first-row transition elements including Ni, Fe, Co, Mn, and Ti. The very large changes in both reflectance and transmittance on loading these films with hydrogen are accompanied by significant structural and electronic transformations. The valence states and coordination of metal atoms during hydrogen loading were followed using dynamic in situ transmissionmode X-ray absorption spectroscopy. Time-resolved Mg K-edge and Ni, Co, Mn, and Ti L-edge spectra reflect both reversible and irreversible changes in the metal environments. These spectra are compared to those of reference materials and to predictions from calculations. JF - Fifth International Meeting on Electrochromism CY - Golden, CO U1 -

Windows and Daylighting Group

U2 - LBNL-51415 DO - 10.1016/j.ssi.2003.08.041 ER - TY - JOUR T1 - X-Ray Absorption Spectroscopy of Transition Metal-Magnesium Hydride Thin Films JF - Journal of Alloys and Compounds Y1 - 2003/08// SP - 204 EP - 207 A1 - Thomas J. Richardson A1 - Baker Farangis A1 - Jonathan L. Slack A1 - Ponnusamy Nachimuthu A1 - Rupert C.C. Perera A1 - Nobumichi Tamura A1 - Michael D. Rubin KW - EXAFS KW - Hydrogen storage materials KW - NEXAFS KW - thin films KW - x-ray diffraction AB - Mixed metal thin films containing magnesium and a first-row transition element exhibit very large changes in both reflectance and transmittance on exposure to hydrogen gas. Changes in electronic structure and coordination of the magnesium and transition metal atoms during hydrogen absorption were studied using dynamic in situ transmission mode X-ray absorption spectroscopy. Mg K-edge and Ni, Co, and Ti L-edge spectra reflect both reversible and irreversible changes in the metal environments. A significant shift in the nickel L absorption edge shows it to be an active participant in hydride formation. The effect on cobalt and titanium is much less dramatic, suggesting that these metals act primarily as catalysts for formation of magnesium hydride. VL - 356-357 U1 -

Windows and Daylighting Group

U2 - LBNL-50574 DO - 10.1016/S0925-8388(02)01237-9 ER - TY - JOUR T1 - The Influence of Nitrogen Ion Energy on the Quality of GaN Films Grown with Molecular Beam Epitaxy JF - Journal of Electronic Materials Y1 - 1995/04// SP - 249 EP - 255 A1 - T.C. Fu A1 - Nathan Newman A1 - Erin C. Jones A1 - James S. Chan A1 - Xiaohong Liu A1 - Michael D. Rubin A1 - Nathan W. Cheung A1 - Eicke R. Weber KW - Activated nitrogen KW - GaN KW - molecular beam epitaxy (MBE) KW - nitrogen ion energy AB - Since the growth of GaN using molecular beam epitaxy (MBE) occurs under metastable growth conditions, activated nitrogen is required to drive the forward synthesis reaction. In the process of exciting the nitrogen using a plasma or ion-beam source, species with large kinetic energies are generated. Impingement on the growth surface by these species can result in subsurface damage to the growing film, as well as an enhancement of the reverse decomposition reaction rate. In this study, we investigate the effect of the kinetic energy of the impinging nitrogen ions during growth on the resulting optical and structural properties of GaN films. Strong band-edge photoluminescence and cathodoluminescence are found when a kinetic energy of ~10 eV are used, while luminescence is not detectable when the kinetic energies exceeds 18 eV. Also, we find that the use of conductive SiC substrates results in more homogeneous luminescence than the use of insulating sapphire substrates. This is attributed to sample surface charging in the case of sapphire substrates and subsequent variation in the incident ion flux and kinetic energy across the growth surface.This study clearly shows that the quality of GaN films grown by MBE are presently limited by damage from the impingement of high energy species on the growth surface. VL - 24 IS - 4 U1 -

Windows and Daylighting Group

U2 - LBL-37223 DO - 10.1007/BF02659683 ER - TY - JOUR T1 - Thermal Annealing Characteristics of Si and Mg-implanted GaN Thin Films JF - Applied Physics Letters Y1 - 1996/03// SP - 2702 EP - 2704 A1 - James S. Chan A1 - Nathan W. Cheung A1 - Lawrence F. Schloss A1 - Erin C. Jones A1 - William S. Wong A1 - Nathan Newman A1 - Xiaohong Liu A1 - Eicke R. Weber A1 - A. Gassman A1 - Michael D. Rubin KW - annealing KW - crystal doping KW - defect states KW - electrical properties KW - gallium nitrides KW - ion implantation KW - magnesium additions KW - microstructure KW - silicon additions AB - In this letter, we report the results of ion implantation of GaN using 28Si and 23Mg species. Structural and electrical characterizations of the GaN thin films after thermal annealing show that native defects in the GaN films dominate over implant doping effects. The formation energies of the annealing induced defects are estimated to range from 1.4 to 3.6 eV. A 30 keV10^14 cm-2 Mg implant results in the decrease of the free-carrier concentration by three orders of magnitude compared to unimplanted GaN up to an annealing temperature of 690 °C. Furthermore, we have observed the correlation between these annealing-induced defects to both improved optical and electrical properties. VL - 68 IS - 19 U1 -

Windows and Daylighting Group

U2 - LBL-37372 DO - 10.1063/1.116314 ER - TY - CONF T1 - Fundamental Materials-Issues Involved in the Growth of GaN by Molecular Beam Epitaxy Y1 - 1994/ A1 - Nathan Newman A1 - T.C. Fu A1 - Z. Liu A1 - Zuzanna Liliental-Weber A1 - Michael D. Rubin A1 - James S. Chan A1 - Erin C. Jones A1 - Jennifer T. Ross A1 - Ian M. Tidswell A1 - Kin Man Yu A1 - Nathan W. Cheung A1 - Eicke R. Weber AB - Gallium nitride is one of the most promising materials for ultraviolet and blue light-emitting diodes and lasers. Both Molecular Beam Epitaxy (MBE) and Metal-Organic Chemical Vapor Deposition (MOCVD) have recently made strong progress in fabricating high-quality epitaxial GaN thin films. In this paper, we review materials-related issues involved in MBE growth. We show that a strong understanding of the unique meta-stable growth process allows us to correctly predict the optimum conditions for epitaxial GaN growth. The resulting structural, electronic and optical properties of the GaN films are described in detail. U2 - LBL-37296 ER - TY - CONF T1 - Comparison of AIN Films Grown by RF at Magnetron Sputtering and Ion-Assisted Molecular Beam Epitaxy T2 - Materials Research Society Y1 - 1993/04// A1 - James S. Chan A1 - T.C. Fu A1 - Nathan W. Cheung A1 - Jennifer T. Ross A1 - Nathan Newman A1 - Michael D. Rubin AB - Crystalline aluminum nitride (AlN) thin films were formed on various substrates by using RF magnetron sputtering of an A1 target in a nitrogen plasma and also by ion-assisted molecular beam epitaxy (IAMBE). Basal-oriented AlN/(111) Si showed a degradation of crystallinity with increased substrate temperature from 550 to 770 °C, while the crystallinity of AlN/(0001) Al2O3 samples improved from 700 to 850 °C. The optical absorption characteristics of the AlN/(0001) Al2O3 films as grown by both deposition methods revealed a decrease in sub-band gap absorption with increased substrate temperature. JF - Materials Research Society CY - San Francisco, CA VL - 300 U1 -

Windows and Daylighting Group

U2 - LBL-35660 ER - TY - JOUR T1 - P-Type Gallium Nitride by Reactive Ion-Beam Molecular Beam Epitaxy with Ion Implantation, Diffusion or Coevaporation of Mg JF - Applied Physics Letters Y1 - 1993/ SP - 64 EP - 66 A1 - Michael D. Rubin A1 - Nathan Newman A1 - James S. Chan A1 - T.C. Fu A1 - Jennifer T. Ross KW - carrier density KW - carrier mobility KW - crystal doping KW - diffusion KW - evaporation KW - gallium nitrides KW - ion implantation KW - magnesium additions KW - molecular beam epitaxy KW - p−type conductors AB - Gallium nitride is one of the most promising materials for ultraviolet and blue light‐emitting diodes and lasers. The principal technical problem that limits device applications has been achieving controllable p‐type doping. Molecular beam epitaxy assisted by a nitrogen ion beam produced p‐type GaN when doped via ion implantation, diffusion, or coevaporation of Mg. Nearly intrinsic p‐type material was also produced without intentional doping, exhibiting hole carrier concentrations of 5×1011 cm−3 and hole mobilities of over 400 cm2/V/s at 250 K. This value for the hole mobility is an order of magnitude greater than previously reported. VL - 64 IS - 1 U1 -

Windows and Daylighting Group

U2 - LBL-34413 JO - Appl. Phys. Lett. DO - 10.1063/1.110870 ER -