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Gallium nitride micro-light-emitting diode structured light sources for multi-modal optical wireless communications systems
摘要： Gallium nitride-based light-emitting diodes (LEDs) have revolutionized the lighting industry with their efficient generation of blue and green light. While broad-area (square millimetre) devices have become the dominant LED lighting technology, fabricating LEDs into micro-scale pixels (micro-LEDs) yields further advantages for optical wireless communications (OWC), and for the development of smart-lighting applications such as tracking and imaging. The smaller active areas of micro-LEDs result in high current density operation, providing high modulation bandwidths and increased optical power density. Fabricating micro-LEDs in array formats allows device layouts to be tailored for target applications and provides additional degrees of freedom for OWC systems. Temporal and spatial control is crucial to use the full potential of these micro-scale sources, and is achieved by bonding to pitch-matched complementary metal-oxide-semiconductor control electronics. These compact, integrated chips operate as digital-to-light converters, providing optical signals from digital inputs. Applying the devices as projection systems allows structured light patterns to be used for tracking and self-location, while simultaneously providing space-division multiple access communication links. The high-speed nature of micro-LED array devices, combined with spatial and temporal control, allows many modes of operation for OWC providing complex functionality with chip-scale devices.
关键词： Gallium nitride,structured light,light-emitting diodes,optical wireless communications
更新于2025-09-23 15:19:57
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Exploring optical properties of Gd doped zincblende GaN for novel optoelectronic applications (A DFT+U study)
摘要： In current research, we investigate optical properties of Gd doped zincblende GaN using Wien2K code, by employing DFT+U. We consider pure GaN and we dope various Gd concentrations 3.12%, 6.25% and 12.5% into the host GaN lattice while supercell size is kept fixed (1×2×2) for all cases. We elaborate and present a detailed comparison among optical and electronic properties of pure GaN with various Gd concentrations. Interaction of Gd and N atoms and localization of d and f states of dopant are remarked near Fermi level or maxima of valence band. In comparison to pure GaN, absorption spectra for 3.12% Gd concentration shows redshift but for highest Gd concentration (6.25% 12.5%), a blueshift in absorption spectrum is noted. Absorption is pronounced and enhanced in the UV region. Study of optical spectra for various optical properties suggest that Gd:GaN system is mostly suitable for UV optoelectronics. Results for optical properties have great similarity with the existing literature works. Our unprecedented and first ever reported results on optical properties of Gd:GaN system, direct future path of this material for its potential uses in UV optoelectronic, photonic, LEDs, UV sterilization application, photosensors, thermochromic solar cells and biochemical sensing industries.
关键词： optical properties,density of states,DFT calculations,gallium nitride (GaN),Gd doping
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE International Ultrasonics Symposium (IUS) - Glasgow, United Kingdom (2019.10.6-2019.10.9)] 2019 IEEE International Ultrasonics Symposium (IUS) - Tiled Large Element 1.75D Aperture with Dual Array Modules by Adjacent Integration of PIN-PMN-PT Transducers and Custom High Voltage Switching ASICs
摘要： A technique is described, to efficiently evaluate the reliability of an RF semiconductor device when several different mechanisms contribute simultaneously to its wearout. This is of interest for present-day GaN HEMT devices because symptoms of several simultaneous degradation mechanisms have been reported widely. The technique involves first finding DC parameters that are “signatures” of each mechanism. Then, separate DC-stress lifetests are performed to find the degradation rates for the signature parameters, at several temperatures, and the corresponding Arrhenius curves. Next, an RF-stress lifetest (with only one stress condition) is performed, while monitoring all of the signature parameters and the RF performance. This is utilized to determine the “scaling factors” between the rates of change in the DC lifetests and the rates of change in the RF application. Applying these scaling factors to the original Arrhenius curves gives an “overall” Arrhenius plot for the RF application with several different lines, for the different degradation mechanisms. The technique can be extended to further degradation mechanisms, by conducting further DC and RF lifetests while monitoring appropriate signature parameters.
关键词： lifetesting,semiconductor device reliability,gallium nitride,Failure analysis,HEMTs
更新于2025-09-23 15:19:57
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First Principle Study of Optical Properties of Cu doped zincblende GaN for Novel Optoelectronic Applications
摘要： Current computational study is focused on calculation of optical properties of Cu doped zincblende GaN system where PBE-GGA approximation is employed in Wien2K code. We consider various Cu concentrations 6.25%, 3.12%, 1.56% corresponding to 1× 1 × 2, 1 × 2 × 2, 2 × 2 × 2 supercell configurations respectively. We substitute one Ga atom with one Cu atom in each concentration and we present a good comparison among optical properties of pure GaN and all Cu concentrations. TDOS and PDOS plots reveal contribution of Ga p-states, N p-states and Cu d-states. Optical absorption shows redshift in comparison to pure GaN and because of interactions of Cu and N atoms, we inspect localized d-states at minima of conduction band or Fermi level. Hence, electro-optical properties of zincblende GaN are enhanced upon addition of impurity (Cu) and the material may potentially be used in photonic, power electronics, solar cells, optoelectronics, UV photodetectors and LEDs.
关键词： Gallium Nitride,DFT calculation,Cu doping,Optical Properties,Density of states
更新于2025-09-23 15:19:57
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Effect of Horizontal p-n Junction on Optoelectronics Characteristics in InGaN-Based Light-Emitting Diodes with V-shaped Pits
摘要： Two InGaN-based light-emitting diodes (LEDs) with and without pre-layer were prepared, and both had a similar multi-quantum well (MQW) structure with four green QWs near n-GaN and one blue QW close to p-GaN. The pre-layer established large V-shaped pits in MQWs. In addition to the regular vertical p-n junction along c-axis, a kind of horizontal p-n junction created by n-type MQWs and p-GaN filled in V-shaped pits was introduced. And the effect of the horizontal p-n junction on optoelectronics characteristics, including photoluminescence, electroluminescence, and ??-??, were discussed. The horizontal p-n junction creates a strong horizontal built-in electric field which can effectively separate the photogenerated carriers in the QW close to p-GaN, leading to the absence of photoluminescence from the QW close to p-GaN. The horizontal p-n junction also provides a path for hole injection, which changes the turn-on order of QW, and reduces the voltage of the LED with large V-shaped pits. These results suggest a new thought of analyzing and designing InGaN-based LEDs with V-shaped pits.
关键词： light-emitting diode,V-shaped pit,indium gallium nitride,built-in electric field
更新于2025-09-23 15:19:57
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Benefits of Considering More than Temperature Acceleration for GaN HEMT Life Testing
摘要： The purpose of this work was to investigate the validity of Arrhenius accelerated-life testing when applied to gallium nitride (GaN) high electron mobility transistors (HEMT) lifetime assessments, where the standard assumption is that only critical stressor is temperature, which is derived from operating power, device channel-case, thermal resistance, and baseplate temperature. We found that power or temperature alone could not explain difference in observed degradation, and that accelerated life tests employed by industry can bene?t by considering the impact of accelerating factors besides temperature. Speci?cally, we found that the voltage used to reach a desired power dissipation is important, and also that temperature acceleration alone or voltage alone (without much power dissipation) is insuf?cient to assess lifetime at operating conditions.
关键词： lifetime testing,device degradation,HEMT,gallium nitride,reliability
更新于2025-09-23 15:19:57
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Temperature dependent control of the solubility of gallium nitride in supercritical ammonia using mixed mineralizer
摘要： Using a mass-loss method, we investigated the solubility change of gallium nitride (GaN) in supercritical ammonia with mixed mineralizers [ammonium chloride (NH4Cl) + ammonium bromide (NH4Br) and NH4Cl + ammonium iodide (NH4I)]. The solubilities were measured over the temperature range 450–550 °C, at 100 MPa. The solubility increased with NH4Cl mole fraction at 450 °C and 100 MPa. The temperature dependence of the solubility curve was then measured at an equal mole ratio of the two mineralizers. The slope of the solubility–temperature relationship in the mixed mineralizer was between those of the individual mineralizers. These results show that the temperature dependence of the solubility of GaN can be controlled by the mineralizer mixture ratio. The results of the van’t Hoff plot suggest that the solubility species were unchanged over the investigated temperature range. Our approach might pave the way to realizing large, high-quality GaN crystals for future gallium-nitride electronic devices, which are increasingly on demand in the information-based age.
关键词： Acidic mineralizer,Gallium nitride,Ammonothermal,Solubility,Supercritical ammonia
更新于2025-09-19 17:15:36
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Electrophysical and Physical-Chemical Properties of Ohmic Contacts to III-N Compounds
摘要： Experimental data on studying ohmic contacts based on single-layer and multilayer metallizations on GaN and (In, Al, Ga)N solid solutions are analyzed. The contact resistance of the Ti/Al/Mo/Au and Ti/Al/Mo/W/Au metallizations on undoped GaN is studied. The dependences of the contact resistance on the GaN surface treatment before the metallization and on the metallization annealing regimes are investigated.
关键词： gallium nitride,surface treatment,(AlInGa)N solid solutions,ohmic contacts,metallization,charge neutrality level
更新于2025-09-19 17:15:36
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[IEEE 2019 5th International Conference on Advances in Electrical Engineering (ICAEE) - Dhaka, Bangladesh (2019.9.26-2019.9.28)] 2019 5th International Conference on Advances in Electrical Engineering (ICAEE) - Comparative Study of Different Transformer-less Inverter Topologies for Grid-tied Photovoltaic System
摘要： An inductively coupled contactless dc connector has been proposed for the next-generation 380-V dc distribution system in data centers. A LLC resonant dc–dc converter topology with gallium nitride (GaN) power transistors has been applied to realize the short-distance highly ef?cient contactless power transfer. A prototype of a 1.2-kW 384- to 192-V connector has been fabricated and the conversion ef?ciency of over 95% with the power density of 8.1 W/cm3 has been con?rmed experimentally under 1000-kHz operation. The design consideration has been carried out and the potential to achieve 10.0 W/cm3 has been also shown taking the feature of the GaN power device and the characteristics of the magnetic core material for the transformer into account. The contactless dc connector integrates the functioning of an isolated dc–dc converter into a connector for space saving, and the dc current can be cut off without arc because of the inductive coupling. The proposed connector contributes to realizing a highly ef?cient, space saving, and reliable future 380-V dc distribution system.
关键词： Contactless power supply,dc–dc power converters,dc power distribution,gallium nitride (GaN)
更新于2025-09-19 17:13:59
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[IEEE 2017 IEEE 44th Photovoltaic Specialists Conference (PVSC) - Washington, DC (2017.6.25-2017.6.30)] 2017 IEEE 44th Photovoltaic Specialist Conference (PVSC) - Characterization and redesign of perovskite/silicon tandem cells
摘要： An inductively coupled contactless dc connector has been proposed for the next-generation 380-V dc distribution system in data centers. A LLC resonant dc–dc converter topology with gallium nitride (GaN) power transistors has been applied to realize the short-distance highly ef?cient contactless power transfer. A prototype of a 1.2-kW 384- to 192-V connector has been fabricated and the conversion ef?ciency of over 95% with the power density of 8.1 W/cm3 has been con?rmed experimentally under 1000-kHz operation. The design consideration has been carried out and the potential to achieve 10.0 W/cm3 has been also shown taking the feature of the GaN power device and the characteristics of the magnetic core material for the transformer into account. The contactless dc connector integrates the functioning of an isolated dc–dc converter into a connector for space saving, and the dc current can be cut off without arc because of the inductive coupling. The proposed connector contributes to realizing a highly ef?cient, space saving, and reliable future 380-V dc distribution system.
关键词： dc power distribution,Contactless power supply,dc–dc power converters,gallium nitride (GaN)
更新于2025-09-19 17:13:59