Showing papers on "Diode published in 2015"
TL;DR: In this article, the features and present status of SiC power devices are briefly described, and several important aspects of the material science and device physics of the SiC, such as impurity doping, extended and point defects, and the impact of such defects on device performance and reliability, are reviewed.
Abstract: Power semiconductor devices are key components in power conversion systems. Silicon carbide (SiC) has received increasing attention as a wide-bandgap semiconductor suitable for high-voltage and low-loss power devices. Through recent progress in the crystal growth and process technology of SiC, the production of medium-voltage (600?1700 V) SiC Schottky barrier diodes (SBDs) and power metal?oxide?semiconductor field-effect transistors (MOSFETs) has started. However, basic understanding of the material properties, defect electronics, and the reliability of SiC devices is still poor. In this review paper, the features and present status of SiC power devices are briefly described. Then, several important aspects of the material science and device physics of SiC, such as impurity doping, extended and point defects, and the impact of such defects on device performance and reliability, are reviewed. Fundamental issues regarding SiC SBDs and power MOSFETs are also discussed.
750 citations
TL;DR: It is demonstrated that the electroluminescence (EL) mechanism of the inverted quantum dot light-emitting diodes (QD-LEDs) with a ZnO nanoparticle electron injection/transport layer should be direct charge-injection from charge transport layers into the QDs.
Abstract: Through introducing a probe layer of bis(4,6-difluorophenylpyridinato-N,C2)picolinatoiridium (FIrpic) between QD emission layer and 4, 4-N, N- dicarbazole-biphenyl (CBP) hole transport layer, we successfully demonstrate that the electroluminescence (EL) mechanism of the inverted quantum dot light-emitting diodes (QD-LEDs) with a ZnO nanoparticle electron injection/transport layer should be direct charge-injection from charge transport layers into the QDs. Further, the EL from QD-LEDs at sub-bandgap drive voltages is achieved, which is in contrast to the general device in which the turn-on voltage is generally equal to or greater than its bandgap voltage (the bandgap energy divided by the electron charge). This sub-bandgap EL is attributed to the Auger-assisted energy up-conversion hole-injection process at the QDs/organic interface. The high energy holes induced by Auger-assisted processes can be injected into the QDs at sub-bandgap applied voltages. These results are of important significance to deeply understand the EL mechanism in QD-LEDs and to further improve device performance.
586 citations
TL;DR: This work experimentally demonstrate interlayer band-to-band tunneling in vertical MoS2/WSe2 van der Waals (vdW) heterostructures using a dual-gate device architecture with important implications toward the design of atomically thin tunnel transistors.
Abstract: Two-dimensional layered semiconductors present a promising material platform for band-to-band-tunneling devices given their homogeneous band edge steepness due to their atomically flat thickness. Here, we experimentally demonstrate interlayer band-to-band tunneling in vertical MoS2/WSe2 van der Waals (vdW) heterostructures using a dual-gate device architecture. The electric potential and carrier concentration of MoS2 and WSe2 layers are independently controlled by the two symmetric gates. The same device can be gate modulated to behave as either an Esaki diode with negative differential resistance, a backward diode with large reverse bias tunneling current, or a forward rectifying diode with low reverse bias current. Notably, a high gate coupling efficiency of ∼80% is obtained for tuning the interlayer band alignments, arising from weak electrostatic screening by the atomically thin layers. This work presents an advance in the fundamental understanding of the interlayer coupling and electron tunneling in ...
556 citations
TL;DR: 2,6-Diphenylanthracene OLED arrays are successfully driven by DPA field-effect transistor arrays, demonstrating that DPA is a high mobility emissive organic semiconductor with potential in organic optoelectronics.
Abstract: The integration of high charge carrier mobility and high luminescence in an organic semiconductor is challenging. However, there is need of such materials for organic light-emitting transistors and organic electrically pumped lasers. Here we show a novel organic semiconductor, 2,6-diphenylanthracene (DPA), which exhibits not only high emission with single crystal absolute florescence quantum yield of 41.2% but also high charge carrier mobility with single crystal mobility of 34 cm(2) V(-1) s(-1). Organic light-emitting diodes (OLEDs) based on DPA give pure blue emission with brightness up to 6,627 cd m(-2) and turn-on voltage of 2.8 V. 2,6-Diphenylanthracene OLED arrays are successfully driven by DPA field-effect transistor arrays, demonstrating that DPA is a high mobility emissive organic semiconductor with potential in organic optoelectronics.
378 citations
TL;DR: This method reliably and reproducibly achieve rectification ratios in excess of 200 at voltages as low as 370 mV using a symmetric oligomer of thiophene-1,1-dioxide and provides a general route for tuning nonlinear nanoscale device phenomena.
Abstract: Single-molecule diodes with rectification ratios over 200 at low voltages can be obtained with symmetric molecules by creating an environmental asymmetry using electric double-layers.
346 citations
TL;DR: In this article, high-Hall-electron-mobility and high-performance Schottky barrier diodes for edge-defined β-Ga2O3 single crystals have been demonstrated.
Abstract: High-Hall-electron-mobility and high-performance Schottky barrier diodes for edge-defined fed-grown () β-Ga2O3 single crystals have been demonstrated. A high electron mobility of 886 cm2/(Vs) at 85 K was obtained. By theoretical specific scattering mechanisms, it was found that the electron mobility for >200 K is limited by optical phonon scattering and that for <100 K by ionized impurity scattering. On Schottky barrier diodes with Ni contacts, the current density for the forward voltage was 70.3 A/cm2 at 2.0 V, and a nearly ideal ideality factor of 1.01 was obtained.
236 citations
TL;DR: A large transmission modulation of 83% is obtained in the graphene–silicon hybrid film, which exhibits tremendous potential for applications in designing broadband terahertz modulators and switchable terAhertz plasmonic and metamaterial devices.
Abstract: Controlling the propagation properties of the terahertz waves in graphene holds great promise in enabling novel technologies for the convergence of electronics and photonics. A diode is a fundamental electronic device that allows the passage of current in just one direction based on the polarity of the applied voltage. With simultaneous optical and electrical excitations, we experimentally demonstrate an active diode for the terahertz waves consisting of a graphene-silicon hybrid film. The diode transmits terahertz waves when biased with a positive voltage while attenuates the wave under a low negative voltage, which can be seen as an analogue of an electronic semiconductor diode. Here, we obtain a large transmission modulation of 83% in the graphene-silicon hybrid film, which exhibits tremendous potential for applications in designing broadband terahertz modulators and switchable terahertz plasmonic and metamaterial devices.
216 citations
TL;DR: In this paper, a flip-chip architecture for violet-emitting III-nitride (III-N) lightemitting diodes (LEDs) was proposed for high current density and high temperature.
Abstract: We report on violet-emitting III-nitride light-emitting diodes (LEDs) grown on bulk GaN substrates employing a flip-chip architecture. Device performance is optimized for operation at high current density and high temperature, by specific design consideration for the epitaxial layers, extraction efficiency, and electrical injection. The power conversion efficiency reaches a peak value of 84% at 85 °C and remains high at high current density, owing to low current-induced droop and low series resistance.
194 citations
TL;DR: The fabrication of bright single-photon emitting diodes that display fully polarized output, superior photon statistics, and stability in both continuous and pulsed modes, all at room temperature are demonstrated.
Abstract: Electrically driven single-photon emitting devices have immediate applications in quantum cryptography, quantum computation and single-photon metrology. Mature device fabrication protocols and the recent observations of single defect systems with quantum functionalities make silicon carbide an ideal material to build such devices. Here, we demonstrate the fabrication of bright single-photon emitting diodes. The electrically driven emitters display fully polarized output, superior photon statistics (with a count rate of >300 kHz) and stability in both continuous and pulsed modes, all at room temperature. The atomic origin of the single-photon source is proposed. These results provide a foundation for the large scale integration of single-photon sources into a broad range of applications, such as quantum cryptography or linear optics quantum computing.
177 citations
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TL;DR: In this article, a spin-wave diode, which produces no Joule heating, is presented, and a new design for a spin wave diode is proposed, which can be used to produce no waste heat.
Abstract: Conventional electric circuits use electrons as information carriers, a process that dissipates vast quantities of waste heat. A new design for a spin-wave diode, which produces no Joule heating, is presented.
159 citations
TL;DR: The findings enable the best optimized flexible diodes to reach 6.3 GHz at zero bias, which is beyond the critical benchmark speed of 2.45 GHz to satisfy the principal frequency bands of smart phones such as those for cellular communication, Bluetooth, Wi-Fi and global satellite positioning.
Abstract: Mechanically flexible mobile phones have been long anticipated due to the rapid development of thin-film electronics in the last couple of decades. However, to date, no such phone has been developed, largely due to a lack of flexible electronic components that are fast enough for the required wireless communications, in particular the speed-demanding front-end rectifiers. Here Schottky diodes based on amorphous indium-gallium-zinc-oxide (IGZO) are fabricated on flexible plastic substrates. Using suitable radio-frequency mesa structures, a range of IGZO thicknesses and diode sizes have been studied. The results have revealed an unexpected dependence of the diode speed on the IGZO thickness. The findings enable the best optimized flexible diodes to reach 6.3 GHz at zero bias, which is beyond the critical benchmark speed of 2.45 GHz to satisfy the principal frequency bands of smart phones such as those for cellular communication, Bluetooth, Wi-Fi and global satellite positioning.
TL;DR: P polarized, directional and resonantly enhanced light emission from inelastic electron tunnelling are achieved and a novel platform for studying the interaction of electrons with strongly localized electromagnetic fields is established.
Abstract: The ultrafast conversion of electrical signals to optical signals at the nanoscale is of fundamental interest for data processing, telecommunication and optical interconnects. However, the modulation bandwidths of semiconductor light-emitting diodes are limited by the spontaneous recombination rate of electron-hole pairs, and the footprint of electrically driven ultrafast lasers is too large for practical on-chip integration. A metal-insulator-metal tunnel junction approaches the ultimate size limit of electronic devices and its operating speed is fundamentally limited only by the tunnelling time. Here, we study the conversion of electrons (localized in vertical gold-hexagonal boron nitride-gold tunnel junctions) to free-space photons, mediated by resonant slot antennas. Optical antennas efficiently bridge the size mismatch between nanoscale volumes and far-field radiation and strongly enhance the electron-photon conversion efficiency. We achieve polarized, directional and resonantly enhanced light emission from inelastic electron tunnelling and establish a novel platform for studying the interaction of electrons with strongly localized electromagnetic fields.
TL;DR: In this article, a deep-ultraviolet (DUV) aluminum gallium nitride-based light-emitting diodes (LEDs) on transparent aluminum nitride (AlN) substrates with high light extraction efficiency and high power are proposed and demonstrated.
Abstract: Deep-ultraviolet (DUV) aluminum gallium nitride-based light-emitting diodes (LEDs) on transparent aluminum nitride (AlN) substrates with high light extraction efficiency and high power are proposed and demonstrated The AlN bottom side surface configuration, which is composed of a hybrid structure of photonic crystals and subwavelength nanostructures, has been designed using finite-difference time-domain calculations to enhance light extraction We have experimentally demonstrated an output power improvement of up to 196% as a result of the use of the embedded high-light-extraction hybrid nanophotonic structure The DUV-LEDs produced have demonstrated output power as high as 90 mW in DC operation at a peak emission wavelength of 265 nm
TL;DR: In this article, an interleaved high step-up DC-DC converter based on three-winding high-frequency coupled inductor and voltage multiplier cell (VMC) techniques is presented.
Abstract: This study presents an interleaved high step-up DC–DC converter based on three-winding high-frequency coupled inductor and voltage multiplier cell (VMC) techniques. The primary and secondary windings of each coupled inductor are inserted in the same phase and the third winding is inserted in the other phase. The VMC in each phase consists of two diodes, two capacitors, the secondary winding of the same phase coupled inductor and the third winding of the other phase coupled inductor. The voltage gain is increased and the output voltage is clamped across the capacitors of the VMCs. Then, the voltage across the power metal oxide semiconductor field effect transistors (MOSFETs) is decreased. The leakage inductance of the coupled inductors controls the output diode falling rate, which alleviates reverse recovery problems. The power MOSFETs are turned-on under zero current switching that helps to conversion efficiency improvement. Three modes of operation named as continuous conduction mode, discontinuous conduction mode and boundary conduction mode are investigated for the proposed converter. The carried mathematical analysis and satisfying operation of the proposed converter are verified via experimental results of an 870 W 60 V-input to 590 V-output laboratory prototype with 95.2% conversion efficiency.
TL;DR: In this article, an advanced edge termination technology has been developed by combining plasma treatment, tetramethylammonium hydroxide wet etching, and ion implantation to suppress the leakage along the etch sidewall.
Abstract: Conventional GaN vertical devices, though promising for high-power applications, need expensive GaN substrates. Recently, low-cost GaN-on-Si vertical diodes have been demonstrated for the first time. This paper presents a systematic study to understand and control the OFF-state leakage current in the GaN-on-Si vertical diodes. Various leakage sources were investigated and separated, including leakage through the bulk drift region, passivation layer, etch sidewall, and transition layers. To suppress the leakage along the etch sidewall, an advanced edge termination technology has been developed by combining plasma treatment, tetramethylammonium hydroxide wet etching, and ion implantation. With this advanced edge termination technology, an OFF-state leakage current similar to Si, SiC, and GaN lateral devices has been achieved in the GaN-on-Si vertical diodes with over 300 V breakdown voltage and 2.9-MV/cm peak electric field. The origin of the remaining OFF-state leakage current can be explained by a combination of electron tunneling at the p-GaN/drift-layer interface and carrier hopping between dislocation traps. The low leakage current achieved in these devices demonstrates the great potential of the GaN-on-Si vertical device as a new low-cost candidate for high-performance power electronics.
15 Apr 2015
TL;DR: In this article, a 3D tomography system was proposed for remote-sensing 3D imaging using three-dimensional tomography (THz) signals using high-coherent THz signals.
Abstract: Photoconductive antennas Nonlinear crystals Quantum cascade lasers THz diodes THz transistors Resonant tunneling diodes Vacuum electronics Plasma-wave devices Metamaterials Plastic fibers THz information and signal processing Low-coherent THz signals Cameras Chemical spectroscopy Industrial applications Wireless communications Remote-sensing 3D tomography system
TL;DR: This report is the first time that the PE performance of s-PhOLED approaches 100 lm W−1 high level, even superior to the corresponding state-of-the-art performance of the same color vacuum-deposited PhOLED (v-PholED) counterpart.
Abstract: To realize power efficient solution-processed phosphorescent organic light-emitting diodes (s-PhOLEDs), the corresponding high driving voltage issue should be well solved. To solve it, efforts have been devoted to the exploitation of novel host or interfacial materials. However, the issues of charge trapping of phosphor and/or charge injection barrier are still serious, largely restraining the power efficiency (PE) levels. Herein, with the utilization of an exciplex-forming couple 4, 4′, 4″ -tris[3-methylphenyl(phenyl)amino]triphenylamine (m-MTDATA) and 1,3,5-tri(m-pyrid-3-yl-phenyl)benzene (TmPyPB), the efficient charge injection and transporting, barrier-free hole-electron recombination for the formation of the interfacial exciplex and elimination of charge traps of phosphors in the emissive layer are realized simultaneously, resulting in a turn-on voltage of 2.36 V, a record high PE of 97.2 lm W−1, as well as extremely low driving voltage of 2.60 V at 100 cd m−2, 3.03 V at 1000 cd m−2 and 4.08 V at 10000 cd m−2. This report is the first time that the PE performance of s-PhOLED approaches 100 lm W−1 high level, even superior to the corresponding state-of-the-art performance of the same color vacuum-deposited PhOLED (v-PhOLED) counterpart. We anticipate this report opens a new avenue for achieving power efficient monochromatic and white s-PhOLEDs with simple structures.
Patent•
29 May 2015
TL;DR: An exemplary printable composition of a liquid or gel suspension of diodes comprises a plurality of Diodes, a first solvent and/or a viscosity modifier as discussed by the authors.
Abstract: An exemplary printable composition of a liquid or gel suspension of diodes comprises a plurality of diodes, a first solvent and/or a viscosity modifier. An exemplary apparatus comprises: a plurality of diodes; at least a trace amount of a first solvent; and a polymeric or resin film at least partially surrounding each diode of the plurality of diodes. Various exemplary diodes have a lateral dimension between about 10 to 50 microns and about 5 to 25 microns in height. Other embodiments may also include a plurality of substantially chemically inert particles having a range of sizes between about 10 to about 50 microns.
TL;DR: This paper describes a molecular diode with high, statistically robust, rectification ratios R of 1.1 × 10(3), which operates with a new mechanism of charge transport based on sequential tunneling involving both the HOMO and HOMo-1 positioned asymmetrically inside the junction.
Abstract: This paper describes a molecular diode with high, statistically robust, rectification ratios R of 1.1 × 103. These diodes operate with a new mechanism of charge transport based on sequential tunneling involving both the HOMO and HOMO–1 positioned asymmetrically inside the junction. In addition, the diodes are stable and withstand voltage cycling for 1500 times, and the yield in working junctions is 90%.
TL;DR: Applications of light-emitting diodes in analytical instrumentation cover liquid and gas-phase absorbance measurements, flow-through detectors for chromatography and capillary electrophoresis, sensors, as well as some less often reported methods such as photoacoustic spectroscopy.
TL;DR: In this paper, the nonlinear characteristics of drain-source capacitance in SiC MOSFETs are studied in detail, and the simplified modeling methods for engineering applications are presented.
Abstract: The nonlinear junction capacitances of power devices are critical for the switching transient, which should be fully considered in the modeling and transient analysis, especially for high-frequency applications. The silicon carbide (SiC) MOSFET combined with SiC Schottky Barrier Diode (SBD) is recognized as the proposed choice for high-power and high-frequency converters. However, in the existing SiC MOSFET models only the nonlinearity of gate-drain capacitance is considered meticulously, but the drain–source capacitance, which affects the switching commutation process significantly, is generally regarded as constant. In addition, the nonlinearity of diode junction capacitance is neglected in some simplified analysis. Experiments show that without full consideration of nonlinear junction capacitances, some significant deviations between simulated and measured results will emerge in the switching waveforms. In this paper, the nonlinear characteristics of drain–source capacitance in SiC MOSFET are studied in detail, and the simplified modeling methods for engineering applications are presented. On this basis, the SiC MOSFET model is improved and the simulation results with improved model correspond with the measured results much better than before, which verify the analysis and modeling.
TL;DR: The authors' calculations show that h-BP is a mechanically stable 2D material with a direct band gap of 0.9 eV at the K-point, promising for both electronic and optoelectronic applications.
Abstract: Two-dimensional (2D) materials have attracted growing interest due to their potential use in the next generation of nanoelectronic and optoelectronic applications. On the basis of first-principles calculations based on density functional theory, we first investigate the electronic and mechanical properties of single layer boron phosphide (h-BP). Our calculations show that h-BP is a mechanically stable 2D material with a direct band gap of 0.9 eV at the K-point, promising for both electronic and optoelectronic applications. We next investigate the electron transport properties of a p–n junction constructed from single layer boron phosphide (h-BP) using the non-equilibrium Green's function formalism. The n- and p-type doping of BP are achieved by substitutional doping of B with C and P with Si, respectively. C(Si) substitutional doping creates donor (acceptor) states close to the conduction (valence) band edge of BP, which are essential to construct an efficient p–n junction. By modifying the structure and doping concentration, it is possible to tune the electronic and transport properties of the p–n junction which exhibits not only diode characteristics with a large current rectification but also negative differential resistance (NDR). The degree of NDR can be easily tuned via device engineering.
01 Oct 2015-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: The authors' simulations show that these sensors, the so-called Ultra-Fast Silicon Detectors (UFSD), will be able to reach a time resolution factor of 10 better than that of traditional silicon sensors.
Abstract: Low-Gain Avalanche Diodes (LGAD) are silicon detectors with output signals that are about a factor of 10 larger than those of traditional sensors. In this paper we analyze how the design of LGAD can be optimized to exploit their increased output signal to reach optimum timing performances. Our simulations show that these sensors, the so-called Ultra-Fast Silicon Detectors (UFSD), will be able to reach a time resolution factor of 10 better than that of traditional silicon sensors.
TL;DR: In this paper, the forward characteristics of SiC p-i-n diodes are significantly improved by carrier-lifetime enhancement, and the differential on-resistance is inversely proportional to the square root of current density.
Abstract: Silicon carbide (SiC) p-i-n diodes having five different n−-layer ( $i$ -layer) thicknesses from 48 to $268~\mu $ m are fabricated. The forward characteristics of SiC p-i-n diodes are significantly improved by carrier-lifetime enhancement. After this improvement, the differential on-resistance is inversely proportional to the square root of current density for all the diodes with different thicknesses of n−-layer. As a result, the forward current density–voltage characteristics can be approximately expressed by a parabolic function, as in the case of Si p-i-n diodes. Using a 268- $\mu $ m-thick n−-layer, the lifetime enhancement, and an improved space-modulated junction termination extension structure, a very high blocking voltage over 26.9 kV and low differential on-resistance of 9.7 m $\Omega \cdot $ cm $^{2}$ are achieved.
TL;DR: Low Gain Avalanche Detectors (LGADs) as discussed by the authors are based on a n++-p+-p structure where appropriate doping of multiplication layer (p^+) is needed to achieve high fields and impact ionization.
Abstract: Novel silicon detectors with charge gain were designed (Low Gain Avalanche Detectors - LGAD) to be used in particle physics experiments, medical and timing applications. They are based on a n++-p+-p structure where appropriate doping of multiplication layer (p^+) is needed to achieve high fields and impact ionization. Several wafers were processed with different junction parameters resulting in gains of up to 16 at high voltages. In order to study radiation hardness of LGAD, which is one of key requirements for future high energy experiments, several sets of diodes were irradiated with reactor neutrons, 192 MeV pions and 800 MeV protons to the equivalent fluences of up to Φeq=1016 cm−2. Transient Current Technique and charge collection measurements with LHC speed electronics were employed to characterize the detectors. It was found that the gain decreases with irradiation, which was attributed to effective acceptor removal in the multiplication layer. Other important aspects of operation of irradiated detectors such as leakage current and noise in the presence of charge multiplication were also investigated.
TL;DR: In this article, the authors have studied the admittance and current-voltage characteristics of the Au/Ti/Al2O3/nGaAs structure and obtained the barrier height (BH) and ideality factor values of 1.18 eV and 2.45 were obtained from the forward-bias ln I vs V plot at 300 K.
TL;DR: Hetero-CMOS inverters with electrically isolated FETs demonstrate novel and superior device performances of a maximum voltage gain as ∼27, sub-nanowatt power consumption, almost ideal noise margin approaching 0.5VDD, and digital logic and push-pull circuits for organic light-emitting diode switching, directly displaying the prospective of practical applications.
Abstract: Two-dimensional (2D) semiconductor materials with discrete bandgap become important because of their interesting physical properties and potentials toward future nanoscale electronics. Many 2D-based field effect transistors (FETs) have thus been reported. Several attempts to fabricate 2D complementary (CMOS) logic inverters have been made too. However, those CMOS devices seldom showed the most important advantage of typical CMOS: low power consumption. Here, we adopted p-WSe2 and n-MoS2 nanosheets separately for the channels of bottom-gate-patterned FETs, to fabricate 2D dichalcogenide-based hetero-CMOS inverters on the same glass substrate. Our hetero-CMOS inverters with electrically isolated FETs demonstrate novel and superior device performances of a maximum voltage gain as ∼27, sub-nanowatt power consumption, almost ideal noise margin approaching 0.5VDD (supply voltage, VDD=5 V) with a transition voltage of 2.3 V, and ∼800 μs for switching delay. Moreover, our glass-substrate CMOS device nicely performed digital logic (NOT, OR, and AND) and push-pull circuits for organic light-emitting diode switching, directly displaying the prospective of practical applications.
TL;DR: In this article, a magnetic tunnel junction based spin-transfer torque diode with a magnetic skyrmion as ground state and a perpendicular polarizer patterned as nano-contact was proposed for a local injection of the current.
Abstract: Magnetic skyrmions are topologically protected states that are very promising for the design of the next generation of ultra-low-power electronic devices. In this letter, we propose a magnetic tunnel junction based spin-transfer torque diode with a magnetic skyrmion as ground state and a perpendicular polarizer patterned as nano-contact for a local injection of the current. The key result is the possibility to achieve sensitivities (i.e., detection voltage over input microwave power) larger than 2000 V/W for optimized contact diameters. We also pointed out that large enough voltage controlled magnetocrystalline anisotropy could significantly improve the sensitivity. Our results can be very useful for the identification of a class of spin-torque diodes with a non-uniform ground state and to understand the fundamental physics of the skyrmion dynamical properties.
TL;DR: This work demonstrates that this limitation can be overcome by m-planar core-shell InGaN/GaN nanowire LEDs grown on Si(111) to underline the potential of these devices for optical data communication in polymer fibers and free space.
Abstract: The high speed on–off performance of GaN-based light-emitting diodes (LEDs) grown in c-plane direction is limited by long carrier lifetimes caused by spontaneous and piezoelectric polarization. This work demonstrates that this limitation can be overcome by m-planar core–shell InGaN/GaN nanowire LEDs grown on Si(111). Time-resolved electroluminescence studies exhibit 90–10% rise- and fall-times of about 220 ps under GHz electrical excitation. The data underline the potential of these devices for optical data communication in polymer fibers and free space.
TL;DR: A pathway for large-scale fabrication of solid state lighting and optoelectronics on metal foils or sheets is demonstrated and high-quality, vertically aligned GaN nanowires on molybdenum and titanium films are revealed.
Abstract: Bottom-up nanowires are attractive for realizing semiconductor devices with extreme heterostructures because strain relaxation through the nanowire sidewalls allows the combination of highly lattice mismatched materials without creating dislocations. The resulting nanowires are used to fabricate light-emitting diodes (LEDs), lasers, solar cells, and sensors. However, expensive single crystalline substrates are commonly used as substrates for nanowire heterostructures as well as for epitaxial devices, which limits the manufacturability of nanowire devices. Here, nanowire LEDs directly grown and electrically integrated on metal are demonstrated. Optical and structural measurements reveal high-quality, vertically aligned GaN nanowires on molybdenum and titanium films. Transmission electron microscopy confirms the composition variation in the polarization-graded AlGaN nanowire LEDs. Blue to green electroluminescence is observed from InGaN quantum well active regions, while GaN active regions exhibit ultraviolet emission. These results demonstrate a pathway for large-scale fabrication of solid state lighting and optoelectronics on metal foils or sheets.