Efficient Diodes Research Articles

The Role of Self-Assembly Monolayers (SAM) on Schottky Diode Performance

This study investigates the electrical and charge transport properties of Schottky diodes with a p-Si/TiO2/SAM/Al structure, incorporating the self-assembly monolayers (SAMs) 4", 4""-[biphenyl-4,4" diylbis(phenylimino)]dibiphenyl-4-carboxylic acid (MZ187) onto a titanium dioxide (TiO2) layer synthesized via the sol-gel method. The impact of the MZ187 molecule on diode performance was evaluated based on parameters such as the barrier height (∅b), ideality factor (n), and series resistance (Rs). Experimental results reveal that the MZ187 monolayers on TiO2 substantially enhanced diode performance, reducing the n from 3.7 for the control diode to 2.7 for the MZ187-modified diode. The Rs was also significantly reduced, while the ∅b increased. The rectification ratio increased from 1.3x102 for the control diode to 2.2x103 for the MZ187 modified diode. These improvements are attributed to the ability of MZ187 molecules to minimize interface states (Nss) and improve surface quality. These findings underscore the critical role of SAMs in optimizing Schottky diode performance and demonstrate how the MZ187 molecule enhances diode efficiency by altering interface properties. The effectiveness of SAM coatings in enhancing Schottky diode performance makes a significant contribution to the field of nanoelectronics. This research paves the way for future studies on the use of SAMs in various nano electronic applications and offers promising potential for improving the performance and reliability of these technologies.

Improving the light extraction efficiency of white-light perovskite light-emitting diodes based on quantum dot nanowires.

This study introduces an innovative strategy to enhance the light extraction efficiency (LEE) of white-light perovskite light-emitting diodes (PeLEDs) by incorporating quantum dot nanowires (QD-NWs) that are prepared by a porous anodic aluminum (PAA) substrate. The QD-NWs were synthesized through a combination of inkjet printing and vacuum deposition based on the PAA substrate which features a unique waveguiding structure that redirects post-color conversion fluorescence along its axis, effectively minimizing energy losses such as reabsorption loss and total internal reflection (TIR) loss. Empirical evidence indicates a significant luminance enhancement of 43.79%, accompanied by an enhancement in current efficiency, for PeLEDs incorporating the QD-NWs. By fine-tuning the structural attributes of the PAA substrate to regulate the size of QD-NWs, this research has successfully developed white-light PeLEDs based on quasi-2D blue perovskite, offering a universal strategy for boosting LEE and propelling the evolution of white-light PeLED technology.

In Situ, Treatment with Guanidinium Chloride Ligand Enables Efficient Blue Quantum Dot Light-Emitting Diodes with 23.5% External Quantum Efficiency.

The poor efficiency and stability of blue Quantum Dot Light-Emitting diodes (QLED) hinders the practical applications of QLEDs full-color displays. Excessive electron injection, insufficient hole injection, and abundant defects on the surface of quantum dots (QD) are the main issues limiting the performance of blue devices. Herein, an in situ treatment with bipolar small molecule polydentate ligand-guanidine chloride (GACl) is proposed to simultaneously suppress excessive electron injection, patch surface defects of QDs and enhance hole injection. GACl-treated blue QLEDs exhibited a remarkable increase in maximal external quantum Efficiency (EQE) from 16.3% to a record 23.5%, accompanied by maximal luminance (36810cdm-2), excellent maximal current efficiency (17.5cdA-1), and enhanced device stability. Combining C-V and J-V characteristics, a concise physical model of hole injection is also established: Below 3V, hole injection is controlled by the interfacial barrier, primarily through tunneling and thermionic injection; Above 3V, the interfacial barrier is eliminated, and hole injection efficiency is governed by transport within the QD layer. This study showed a clear physical model for understanding the hole injection mechanism in QLEDs, offering valuable design strategies for improving the performance of blue-QLEDs.

Integration of p-Type PdPc and n-Type SnZnO into Hybrid Nanofibers Using Simple Chemical Route for Enhancement of Schottky Diode Efficiency

Palladium phthalocyanine (PdPc) and palladium phthalocyanine integrated with tin–zinc oxide (PdPc:SnZnO) were prepared using a simple chemical approach, and their structural and morphological properties were identified using X-ray diffraction, energy dispersive X-ray analysis, scanning electron microscopy, and transmission electron microscopy techniques. The PdPc:SnZnO nanohybrid revealed a polycrystalline structure combining n-type metal oxide SnZnO nanoparticles with p-type organic PdPc molecules. The surface morphology exhibited wrinkled nanofibers decorated with tiny spheres and had a large aspect ratio. The thin film revealed significant optical absorption within the ultraviolet and visible spectra, with narrow band gaps measured at 1.52 eV and 2.60 eV. The electronic characteristics of Al/n-Si/PdPc/Ag and Al/n-Si/PdPc:SnZnO/Ag Schottky diodes were investigated using the current–voltage dependence in both the dark conditions and under illumination. The photodiodes displayed non-ideal behavior with an ideality factor greater than unity. The hybrid diode showed considerably high rectification ratio of 899, quite a low potential barrier, substantial specific photodetectivity, and high enough quantum efficiency, found to be influenced by dopant atoms and the unique topological architecture of the nanohybrid. The capacitance/conductance–voltage dependence measurements revealed the influence of alternative current signals on trapped centers at the interface state, leading to an increase in charge carrier density.

Joint intelligent optimization design of the active region and electron blocking layer for AlGaN-based deep ultraviolet LEDs

Aiming to enhance the internal quantum efficiency (IQE) of AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs), the active region based on the V-shaped quantum well (QW) and the electron-blocking layer (EBL) structure are jointly optimized using intelligent algorithms in this work. This method focuses on maximizing the IQE of the DUV LEDs by optimizing the geometric and material parameters of multiple QWs (MQWs) and EBL. It is demonstrated that the DUV LED with an optimized structure exhibits smaller band edge tilt for improved wave function overlap in QWs and more effective carrier blocking for reduced electron overflow compared to that with a conventional structure. The results show that, by optimizing the active region and EBL structure using the proposed method, the IQE and maximum radiation intensity of the AlGaN-based DUV LED are enhanced by 38% and 41% at 200 A/cm2 injection current density, respectively.

Enhancing light out-coupling in flexible organic light emitting devices through the localized surface plasmon resonance of urchin-like gold nanoparticles

The local surface plasmon resonance (LSPR) effect and scattering properties of gold nanoparticles are effective ways to improve the light extraction efficiency of organic light-emitting diodes (OLEDs). Here five different kinds of urchin-like gold nanoparticles (UGNs) were synthesized using the seed-mediated method. The finite-difference time-domain (FDTD) method was used to calculate the near-field local and far-field scattering properties of various sea urchin-like gold nanoparticles. All five types of UGNs demonstrated certain levels of light enhancement within the visible band. The flexible OLED devices were created by doping five different types of nanoparticles into the flexible substrates. The hollow UGNs device exhibited a maximum current efficiency of 124.25 cd/A, a maximum power efficiency of 131.27 lm/W, and a maximum EQE of 45.54 %. When compared to undoped flexible devices, the maximum current efficiency, the maximum power efficiency, and the maximum EQE increase by 132 %, 82 %, and 36%, respectively. The results indicate that combining the flexible conductive substrate and UGNs is an effective strategy for improving light extraction from flexible OLEDs. This enhancement effect originates from UGNs acting as a scattering layer to reduce total light reflection, and the luminous intensity of the device is improved due to the LSPR of sea urchin-like nanoparticles.

EMPLOYING THIN PLANAR ELECTRODES TO EXPAND THE IONIC WIND FLOW COVERAGE AREA AND ACHIEVE ENHANCED HEAT DISSIPATION

The suboptimal photoelectric conversion efficiency of light-emitting diodes (LEDs) leads to increased temperature. There is a growing interest in using microstructure ionic wind pumps to regulate the chip temperature. But the ionic wind flow and thermal transfer characteristics of thin-plate electrode pumps used for cooling LED chips is unclear. This study proposes ionic wind pumps equipped with wedged and zigzag emitters to effectively manage the heat generated by high-power LED chips. Experimental investigations were conducted to analyze the electrohydrodynamic characteristics of pumps with different emitter types. A two-dimensional model with a wedged electrode and a three-dimensional model with a zigzag electrode were developed for flow distribution analysis and energy efficiency comparison. The cooling capacity of pumps with different configurations was examined. The results show that the pump equipped with a zigzag electrode exhibits improved stability in corona discharge and approximately 1.53 times higher energy efficiency compared to the pump with a wedged electrode. Moreover, the pump with the zigzag electrode covers a larger ionic wind flow area, generating a higher intensity of ionic wind. The angle between the emitter and the grounding electrode significantly affects the ionic wind flow characteristics. The optimal angle is 70° for pumps with wedged emitters and 30° for those with zigzag emitters. Both pumps can produce a steady wall jet at their optimal angle, causing significant disruption in the surrounding area. The pump with a zigzag electrode exhibits superior cooling performance and is more effective with low power consumption.

Superconducting diode effect in the Weyl semimetal Td-MoTe2 that has a surface modulated by Al nanoparticles.

Breaking both inversion and time reversal symmetry could lead to nonreciprocal current transport in a superconductor, where current is dissipationless in one direction and dissipative in the opposite direction, which is called the superconducting diode effect (SDE). We studied SDE in the type-II Weyl semimetal Td-MoTe2 that is covered with Al nanoparticles. Asymmetric V-I characteristics have been measured under a magnetic field. The superconducting diode efficiency reaches as high as 30%. Besides SDE under the out-of-plane field, nonreciprocal supercurrent transport under the in-plane field has been observed. Intriguingly, the maximum SDE occurs in the in-plane field parallel to the current direction, which contradicts present theories. Our work provides further understanding of the origins of the SDE.

Surface Microstructure Enhanced Cryogenic Infrared Light Emitting Diodes for Semiconductor Broadband Upconversion.

Broadband upconversion has various applications in solar photovoltaic, infrared and terahertz detection imaging, and biomedicine. The low efficiency of the light-emitting diodes (LEDs) limits the broadband upconversion performance. In this paper, we propose to use surface microstructures to enhance the electroluminescence efficiency (ELE) of LEDs. Systematical investigations on the cryogenic-temperature performances of microstructure-coupled LEDs, including electroluminescence efficiency, luminescence spectrum, and recombination rate, have been carried out by elaborating their enhancement mechanism and light emitting characteristics both experimentally and theoretically. We have revealed that the reason for the nearly 35% ELE enhancement of the optimized structure under cryogenic temperature and weak injection current is the efficient carrier injection efficiency and the high recombination rate in the active region. We also compare studies of the surface luminescence uniformity of the optimized LED with that of the unoptimized device. This work gives a precise description, and explanation of the performance of the optimized microstructure coupled LED at low temperatures, providing important guidance and inspiration for the optimization of broadband upconverter in the cryogenic temperature region.

Hybrid Functional ITO/Silver Nanowire Transparent Conductive Electrodes for Enhanced Output Efficiency of Ultraviolet GaN-Based Light-Emitting Diodes.

We investigated hybrid functional transparent conductive electrodes (HFTCEs) composed of indium-tin-oxide (ITO) and silver nanowires (AgNWs) for the enhancement of output efficiency in GaN-based ultraviolet light-emitting diodes (UVLEDs). The HFTCEs demonstrated an optical transmittance of 69.5% at a wavelength of 380 nm and a sheet resistance of 16.4 Ω/sq, while the reference ITO TCE exhibited a transmittance of 76.4% and a sheet resistance of 18.7 Ω/sq. Despite the 8.9% lower optical transmittance, the UVLEDs fabricated with HFTCEs achieved a 25% increase in output efficiency compared to reference UVLEDs. This improvement is attributed to the HFTCE's twofold longer current spreading length under operating forward voltages, and more significantly, the enhanced out-coupling of localized surface plasmon (LSP) resonance with the trapped wave-guided light modes.

Monoammonium Modified Dion-Jacobson Quasi-2D Perovskite for High Efficiency Pure-Blue Light Emitting Diodes.

Quasi-2D perovskites exhibit impressive optoelectronic properties and hold significant promise for future light-emitting devices. However, the efficiency of perovskite light-emitting diodes (PeLEDs) is seriously limited by defect-induced nonradiative recombination and imbalanced charge injection. Here, the defect states are passivated and charge injection balance is effectively improved by introducing the additive cyclohexanemethylammonium (CHMA) to bromide-based Dion-Jacobson (D-J) structure quasi-2D perovskite emission layer. CHMA participates in the crystallization of perovskite, leading to high quality film composed of compact and well-contacted grains with enhanced hole transportation and less defects. As a result, the corresponding PeLEDs exhibit stable pure blue emission at 466nm with a maximum external quantum efficiency (EQE) of 9.22%. According to current knowledge, this represents the highest EQE reported for pure-blue PeLEDs based on quasi-2D bromide perovskite thin films. These findings underscore the potential of quasi-2D perovskites for advanced light-emitting devices and pave the way for further advancements in PeLEDs.

Utilization of Optical OFDM Modulation on Blue LED VLC Datacom Without Equalization for 4 m Wireless Link.

To achieve higher visible light communication (VLC) traffic capacity, using the wide bandwidth light-emitting diode (LED) and spectral efficiency modulation signal, is currently the most commonly used method. In this demonstration, we apply the orthogonal frequency division multiplexing quadrature amplitude modulation (OFDM-QAM) with bit- and power-loading algorithm on single blue LED to achieve >1 Gbit/s VLC capacity, when a 400 MHz bandwidth avalanche photodiode (APD)-based receiver (Rx) is exploited for decoding. Here, the higher sensitivity APD can be applied to compensate for the wireless VLC link length in the proposed LED VLC system, and due to the lower LED illumination (255 to 40 lux), is used for the indoor access network after passing the wireless link length of 1 to 4 m. As a result, using single blue LED can achieve 0.962 to 1.057 Gbit/s OFDM rate with available 400 MHz bandwidth APD in poorly illuminated condition indoors without applying analogy equalization.

Star-shaped multifunctional organic emitters based on N-(2-cyanophenyl) carbazole frameworks: Effects of steric hindrance fluorene and heavy-atom bromine

To investigate the effects of steric hindrance fluorene and heavy-atom bromine on the general optoelectronic properties of star-shaped organic emitters based on 9-(2-cyanophenyl) carbazole (OCzPhCN) frameworks, heavy element of bromine and steric hindrance fluorene were introduced into OCzPhCN to produce four derivatives of 2-(3-bromo-9H-carbazol-9-yl)benzonitrile (BrCzPhCN), 2-(3-bromo-6-(9-(4-ethoxyphenyl)-9H-fluoren-9-yl)-9H-carbazol-9-yl)benzonitrile (BrFCzPhCN), 2-(3-(9-(4-ethoxyphenyl)-9H-fluoren-9-yl)-9H-carbazol-9-yl)benzonitrile (FCzPhCN) and 2-(3,6-bis(9-(4-ethoxyphenyl)-9H-fluoren-9-yl)-9H-carbazol-9-yl)benzonitrile (2FCzPhCN). The fluorene units obviously improve the thermal stability of the obtained compounds, and 2FCzPhCN has the highest thermal stability with 5 % mass heat loss temperature reaching 447 °C. In different polar solvents, the absorption peaks wavelength of OCzPhCN, FCzPhCN and 2FCzPhCN are basically unchanged, and the redshifted emission peaks are positively correlated with solvent polarity. The photoluminescence quantum yields (PLQYs) of OCzPhCN, BrCzPhCN, FCzPhCN, BrFCzPhCN and 2FCzPhCN powders were 20.17 %, 5.43 %, 30.75 %, 3.27 % and 23.56 %. The fluorescence and phosphorescent quantum efficiencies of OCzPhCN, BrCzPhCN, FCzPhCN, BrFCzPhCN and 2FCzPhCN powders are 9.76 % and 10.41 %, 1.2 % and 3.23 %, 28.45 % and 2.3 %, 3.27 % and 0 %, 23.56 % and 0 %. OCzPhCN, BrCzPhCN and FCzPhCN powders show obvious room temperature phosphorescent emission, and the phosphorescent emission lifetime of OCzPhCN, BrCzPhCN and FCzPhCN powders at 561 nm, 576 nm and 568 nm are 193.17 ms, 18.65 ms and 7.25 ms. Compared with OCzPhCN, the introduction of bromine decreases the PLQY and the phosphorescent lifetime of BrCzPhCN powder, while the fluorescence quantum efficiency of the compound FCzPhCN powder has been improved. The corresponding single-triplet energy splitting (ΔEST) of OCzPhCN, FCzPhCN and 2FCzPhCN in solutions are 0.49 eV, 0.63 eV and 0.63 eV, and the corresponding ΔEST values of OCzPhCN, BrCzPhCN FCzPhCN powders are 1.19 eV, 0.74 eV and 0.55 eV. The steric hindrance fluorene units result in smaller and stabilized ΔEST in the solid powder states, and the same situation is opposite in the unimolecular solutions. The maximum external quantum efficiency of organic light-emitting diode based on 10,10′-(4,4′-sulfonylbis (4,1-phenylene)) bis (9,9-dimethyl-9,10-dihydroacridine) hosted by OCzPhCN reaches 12.7 %, and the external quantum efficiency at 100 cd/m2 rolls down to 11 %. OCzPhCN is the best emitters in terms of room temperature phosphorescent emission and host applications.

Cascade Effect of a Dimerized Thermally Activated Delayed Fluorescence Dendrimer.

Thermally activated delayed fluorescence (TADF) emitters with a high horizontal orientation are highly essential for improving the external quantum efficiency (EQE) of organic light-emitting diodes; however, pivotal molecular design strategies to improve the horizontal orientation of solution-processable TADF emitters are still scarce and challenging. Herein, a phenyl bridge is adopted to connect the double TADF units, and generate a dimerized TADF dendrimer, D4CzBNPh-SF. Compared to its counterpart with a single TADF unit, the proof-of-the-concept molecule not only exhibits an improved horizontal dipole ratio (78 %) due to the π-delocalization-induced extended molecular conjugation, but also displays a faster reversed intersystem crossing rate constant (6.08×106 s-1) and a high photoluminescence quantum yield of 95 % in neat film. Consequently, the non-doped solution-processed device with D4CzBNPh-SF as the emitter achieves an ultra-high maximum EQE of 32.6 %, which remains at 26.6 % under a luminance of 1000 cd/m2. Furthermore, when using D4CzBNPh-SF as a sensitizer, the TADF-sensitized fluorescence device exhibits a high maximum EQE of 30.7 % at a luminance of 575 cd/m2 and a full width at half maximum of 36 nm.

Study of hybrid nanoscatterer for enhancing light efficiency of quantum dot-converted light-emitting diodes

Optical scatterer additives play a critical role in enhancing the light conversion efficiency and uniformity of quantum dot-converted light-emitting diodes (Qc-LEDs). This study investigates the impact of optical characteristics and morphology of nanoscatterer on the light conversion and extraction efficiency of Qc-LEDs. Various metal oxides and boron nitride nanoparticles and nanoplates with different diffraction index were selected to carry out the study. Finite-Difference Time-Domain (FDTD) simulation was employed to evaluate the scattering effect of various nanosphere and nanoplate scatterers on the optical performance of the Qc-LEDs. The simulation results revealed that the hybrid nanoscatterer integrates the forward-scattering from the nanosphere and backward-scattering of blue light from the nanoplate. Spectral analysis was conducted to examine the optical performance of Qc-LEDs with varying combinations and concentrations of nanoscatterers. TiO2 nanoparticles and Al2O3 nanoplates were found to be the best combination for maximal light conversion and extraction efficiency within Qc-LEDs. The results indicate an optimal light efficiency is obtained with the optimal ratio of 1:2:2 for quantum dots, TiO2 nanoparticles, and Al2O3 nanoplates. These findings reveal the relationship between optical properties, morphology, and light conversion efficiency in Qc-LEDs, highlighting the advantages of the hybrid nanoscatterers for improving optical performance of Qc-LEDs.

Optimum Design of InGaN Blue Laser Diodes with Indium-Tin-Oxide and Dielectric Cladding Layers.

The efficiency of current GaN-based blue laser diodes (LDs) is limited by the high resistance of a thick p-AlGaN cladding layer. To reduce the operation voltage of InGaN blue LDs, we investigated optimum LD structures with an indium tin oxide (ITO) partial cladding layer using numerical simulations of LD device characteristics such as laser power, forward voltage, and wall-plug efficiency (WPE). The wall-plug efficiency of the optimized structure with the ITO layer was found to increase by more than 20% relative to the WPE of conventional LD structures. In the optimum design, the thickness of the p-AlGaN layer decreased from 700 to 150 nm, resulting in a significantly reduced operation voltage and, hence, increased WPE. In addition, we have proposed a new type of GaN-based blue LD structure with a dielectric partial cladding layer to further reduce the optical absorption of a lasing mode. The p-cladding layer of the proposed structure consisted of SiO2, ITO, and p-AlGaN layers. In the optimized structure, the total thickness of the ITO and p-AlGaN layers was less than 100 nm, leading to significantly improved slope efficiency and operation voltage. The WPE of the optimized structure was increased relatively by 25% compared to the WPE of conventional GaN-based LD structures with a p-AlGaN cladding layer. The investigated LD structures employing the ITO and SiO2 cladding layers are expected to significantly enhance the WPE of high-power GaN-based blue LDs.

Influence of different molar concentration on the structural, optical, electrical and photo diode properties of MoO3 thin films

This article discusses an eco-friendly method for creating metal-insulator-semiconductor (MIS) diodes. MoO3 thin films are prepared at different mole concentrations (0.01, 0.03, 0.05 and 0.07 M) using a Jet Nebulizer Spray Pyrolysis (JNSP) methodology. An orthorhombic phase, which is of special interest because of its potential in electronic applications, was discovered by structural investigation using X-ray diffraction (XRD) in the 0.05 M MoO3 film. Field emission scanning electron microscopy (FE-SEM) pictures of the 0.05 M MoO3 film show a distinct nanoplate shape, indicating positive characteristics for photovoltaic applications. UV–Vis spectroscopy revealed an energy bandgap of 3.21 eV for this concentration. This corresponds to the requisite electronic parameters for a high-performance MIS diode. Then the DC electrical conductivity of the films showed a monotonic rise with the concentration of MoO3, peaking at 0.05 M, suggesting improved carrier transport characteristics. The I–V characteristics of the Cu/MoO3/p-Si diodes revealed that current flows mostly across interfaces and is controlled by carrier concentration. The 0.05 M MoO3 substance exhibited a considerable increase in photocurrent. This work explains the optimized MoO3 concentration and the morphology using the JNSP approach can result in the production of highly efficient MIS diodes suited for a wide range of optoelectronic applications.

Large Superconducting Diode Effect in Chiral Carbon Nanotubes

Superconducting electronics are ubiquitous in devices ranging from single-photon detectors to quantum bits. One of the most common superconducting circuit elements is a Josephson junction (JJ)—a junction of two superconductors coupled through either a small normal metal or an insulator. Recently, non-reciprocal switching currents in JJs based on traditional superconductors have been reported, demonstrating a robust diode effect. This so-called Josephson diode effects (JDEs) has since attracted interest to shed light on material and device properties, but also to enable new applications. In this talk, we will present theoretical results on the JDE in chiral carbon nanotubes (CNTs). We find that these CNT-JJs can exhibit large diode efficiencies when an external magnetic field is applied along the nanotube. Additionally, our numerical simulations show that the polarity of the diode can be tuned by electrostatically gating the CNT-JJ. We will discuss the microscopic details that give rise to large diode efficiencies and gate-tunability in chiral CNT-JJs.This work was supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), under Award DE-SC0022245. The work at Sandia is supported by a LDRD project. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.

Significant improvement of n-contact performance and wall plug efficiency of AlGaN-based deep ultraviolet light-emitting diodes by atomic layer etching.

The reactive ion etching (RIE) process is needed to fabricate deep ultraviolet (DUV) light-emitting diodes (LEDs). However, the n-contact performance deteriorates when the high-Al n-AlGaN surface undergoes RIE, leading to decreased LED performance. In this study, we employed an atomic layer etching (ALE) technology to eliminate surface damage generated during the mesa etching process, thus enhancing the n-Al0.65Ga0.35N ohmic contact. The improved contact performance reduced LED operation voltage and mitigated device heat generation. It was observed that DUV LEDs treated with 200 cycles of ALE showed a reduction in operating voltage from 8.3 to 5.2 V at 10 mA, with a knee voltage of 4.95 V. The peak wall plug efficiency (WPE) was approximately 1.74 times that of reference devices. The x-ray photoelectron spectroscopy (XPS) analysis revealed that ALE removed the surface damage layer induced by plasma etching, eliminating surface nitrogen vacancies and increasing surface electron concentration. Consequently, it facilitated better ohmic contact formation on n-Al0.65Ga0.35N. This study demonstrates that the ALE technology achieves etching with minor surface damage and is suitable for use in III-nitride materials and devices to remove surface defects and contaminations, leading to improved device performance.

Josephson Diode Effect in Parallel-Coupled Double-Quantum Dots Connected to Unalike Majorana Nanowires.

We study theoretically the Josephson diode effect (JDE) when realized in a system composed of parallel-coupled double-quantum dots (DQDs) sandwiched between two semiconductor nanowires deposited on an s-wave superconductor surface. Due to the combined effects of proximity-induced superconductivity, strong Rashba spin-orbit interaction, and the Zeeman splitting inside the nanowires, a pair of Majorana bound states (MBSs) may possibly emerge at opposite ends of each nanowire. Different phase factors arising from the superconductor substrate can be generated in the coupling amplitudes between the DQDs and MBSs prepared at the left and right nanowires, and this will result in the Josephson current. We find that the critical Josephson currents in positive and negative directions are different from each other in amplitude within an oscillation period with respect to the magnetic flux penetrating through the system, a phenomenon known as the JDE. It arises from the quantum interference effect in this double-path device, and it can hardly occur in the system of one QD coupled to MBSs. Our results also show that the diode efficiency can reach up to 50%, but this depends on the overlap amplitude between the MBSs, as well as the energy levels of the DQDs adjustable by gate voltages. The present model is realizable within current nanofabrication technologies and may find practical use in the interdisciplinary field of Majorana and Josephson physics.