Performance Of Diodes Research Articles

III-Arsenide separate confinement heterostructure infrared laser diodes with engineered the cladding layers

In this work, III-Arsenide laser diodes (LDs) show better optoelectronic properties when the aluminum (Al) concentration in the cladding layer is increased up to 95 % in a separate confinement heterostructure (SCH). These laser diodes show their peak gain the infrared lasing wavelength of ∼840 nm. Enhancing the Al in the n- and p-cladding layers, both separately and simultaneously in LDs, shows that the optoelectronic properties are reasonably improved. The output light power has been increased to 50 mW at a current density of 13 × 104A/cm2, with 95 % aluminum in both the n- and p-claddings. The modal field intensity has increased by 5 %, and the optical confinement factor (OCF) has improved from 0.0102 to 0.0105 in the proposed device. Consequently, the engineered cladding design, incorporating varied aluminum concentrations, is recognized as pivotal for optimizing the performance of arsenide laser diodes.

Enhancing the Performance of GaN-Based Light-Emitting Diodes by Incorporating a Junction-Type Last Quantum Barrier

In this paper, an n-i-p-type GaN barrier for the final quantum well, which is closest to the p-type GaN cap layer, is proposed for nitride light-emitting diodes (LEDs) to enhance the confinement of electrons and to improve the efficiency of hole injection. The performances of GaN-based LEDs with a traditional GaN barrier and with our proposed n-i-p GaN barrier were simulated and analyzed in detail. It was observed that, with our newly designed n-i-p GaN barrier, the performances of the LEDs were improved, including a higher light output power, a lower threshold voltage, and a stronger electroluminescence emission intensity. The light output power can be remarkably boosted by 105% at an injection current density of 100 A/cm2 in comparison with a traditional LED. These improvements originated from the proposed n-i-p GaN barrier, which induces a strong reverse electrostatic field in the n-i-p GaN barrier. This field not only enhances the confinement of electrons but also improves the efficiency of hole injection.

Enhanced performance of quantum dot light-emitting diodes enabled by zirconium doped SnO2 as electron transport layers.

Next-generation display and lighting based on quantum dot light-emitting diodes (QLEDs) require a balanced electron injection of electron transport layers (ETLs). However, classical ZnO nanoparticles (NPs) as ETLs face inherent defects such as excessive electron injection and positive aging effects, urgently requiring the development of new types of ETL materials. Here, we show that high stability SnO2 NPs as ETL can significantly improve the QLED performance to 100567 cd·m-2luminance, 14.3% maximum external quantum efficiency, and 13.1 cd·A-1 maximum current efficiency using traditional device structures after optimizing the film thickness and annealing the temperature. Furthermore, experimental tests reveal that by doping Zr4+ ions, the size of SnO2 NPs will reduce, dispersion will improve, and energy level will shift up. As expected, when using Zr-SnO2 NPs as the ETL, the maximum external quantum efficiency can reach 16.6%, which is close to the state-of-the-art QLEDs based on ZnO ETL. This work opens the door for developing novel, to the best of our knowledge, type ETLs for QLEDs.

Improved performance in quantum-dot light-emitting diodes through current annealing

The impact of metallic diffusion, stemming from the thermal evaporation process of electrodes, exerts a substantial influence on solution-processed quantum-dot light-emitting diodes (QD-LEDs). This study highlights a significant enhancement in the performance of QD-LEDs achieved through post-metal-evaporation current annealing. The choice of different metal electrodes emerges as a critical factor affecting QD-LED performance during current annealing. In the case of red QD-LEDs with an Al cathode, the maximum external quantum efficiency (EQE) surged from 7.0% to an impressive 14.1%. Conversely, QD-LEDs with an Ag cathode exhibited a more modest improvement, progressing from 10.8% to 12.4%. Notably, an Al/Ag composite electrodes demonstrated the potential for further enhancement, achieving a remarkable maximum EQE of 18.3%. The observed performance improvements can be attributed to the formation of metal diffusion-induced Al-doped ZnO, facilitating electron injection, and Al-oxidized passivated quantum dots (QDs), effectively mitigating metal-induced quenching following current annealing. This study conclusively demonstrates that the application of current annealing can effectively counteract the adverse effects of metal diffusion in QD-LEDs, presenting itself as a promising method for elevating the overall performance of quantum-dot light-emitting diodes.

Effect of annealing on the electrical performance of N-polarity GaN Schottky barrier diodes

A nitrogen-polarity (N-polarity) GaN-based high electron mobility transistor (HEMT) shows great potential for high-frequency solid-state power amplifier applications because its two-dimensional electron gas (2DEG) density and mobility are minimally affected by device scaling. However, the Schottky barrier height (SBH) of N-polarity GaN is low. This leads to a large gate leakage in N-polarity GaN-based HEMTs. In this work, we investigate the effect of annealing on the electrical characteristics of N-polarity GaN-based Schottky barrier diodes (SBDs) with Ni/Au electrodes. Our results show that the annealing time and temperature have a large influence on the electrical properties of N-polarity GaN SBDs. Compared to the N-polarity SBD without annealing, the SBH and rectification ratio at ±5 V of the SBD are increased from 0.51 eV and 30 to 0.77 eV and 7700, respectively, and the ideal factor of the SBD is decreased from 1.66 to 1.54 after an optimized annealing process. Our analysis results suggest that the improvement of the electrical properties of SBDs after annealing is mainly due to the reduction of the interface state density between Schottky contact metals and N-polarity GaN and the increase of barrier height for the electron emission from the trap state at low reverse bias.

Improved performance of quasi-two dimensional perovskite light-emitting diodes with l-phenylalanine-doped PEDOT:PSS hole transport layer

Improved performance of quasi-two dimensional perovskite light-emitting diodes with l-phenylalanine-doped PEDOT:PSS hole transport layer

Reconfigurable Multifunctional Transmission Metasurface Polarizer Integrated with PIN Diodes Operating at Identical Frequencies

Herein, a reconfigurable multifunctional transmission metasurface polarizer, structured with double Jerusalem crosses and integrated with four PIN diodes, is presented. The bottom Jerusalem cross is rotated by 35∘ with respect to the top cross. Both numerical and experimental observations reveal that a linearly polarized (LP) outgoing wave is transmitted at approximately 4.0 GHz when subjected to a left-handed circularly polarized (LCP) or right-handed circularly polarized (RCP) incident wave. The transmission efficiency reaches -2.5 dB when all elements are in the ON state. Furthermore, active control of switchable PIN diodes operating in various statuses unequivocally demonstrates the ability to convert an incident wave polarized in the x or y direction to a LCP or RCP wave, respectively, within the identical frequency band, spanning from 3.6 GHz to 4.3 GHz. This conversion is achieved with a transmission coefficient of -3.5 dB or -4.2 dB at the peak frequency. The proposed metasurface polarizer presents a potentially dynamic method for simultaneously manipulating various polarization conversions of electromagnetic (EM) waves within a desired frequency band.

Light emitting diode and laser diode system behaviour description and their performance signature measurements

Abstract This paper has clarified the light emitting diode and laser diode system behaviour description and their external quantum efficiency measurements. Light output of LED spontaneous emission and laser diode stimulated emission are clarified. Stimulated and amplified spontaneous emission of laser diode and LED system configuration are demonstrated. The management of hybrid light sources spectrum illumination interaction for efficient solar cells light intensity and short circuit current density enhancement. The laser diode has presented better performance in the light output power especially under the same temperature effects. It is ensured that the dramatic effects of the temperature on both laser diode performance efficiency.

Single-event burnout in homojunction GaN vertical PiN diodes with hybrid edge termination design

GaN devices play a major role in modern electronics, providing high-power handling, efficient high-frequency operation, and resilience in harsh environments. However, electric field crowding at the edge of the anode often limits its full potential, leading to single-event effects (SEEs) at lower bias voltages under heavy ion radiation. Here, we report on the performance of homojunction GaN vertical PiN diodes with a hybrid edge termination design under heavy ion irradiation, specifically, oxygen ions, chlorine ions, Cf-252 fission fragments, and alpha particles from an Am-241 source. The unique hybrid edge termination (HET) design provides better electric field management, preventing breakdown from occurring at the edge of the anode at lower voltages. The results of this study reveal that these devices exhibit excellent tolerance to 12-MeV oxygen and 16-MeV chlorine ions, owing to their low linear energy transfer (LET) and range in GaN. However, single-event burnout (SEB) is observed during the Cf-252 exposure at about 50% of the diodes' electrical breakdown voltage due to the presence of higher LET and longer-range ions. Optical and scanning electron microscopy (SEM) reveal that the damage that caused by SEB lies close to the center of these devices rather than the anode edge. Devices with junction termination extension (JTE) instead of HET edge termination also show similar SEB when irradiated with Cf-252 fission fragments. Physical damage due to SEB occurs at the edge of the anode for these devices. These comparative results show the benefits of HET for enhancing the resistance of GaN-based PiN diodes to heavy ion irradiation.

A practical theoretical model for Ge-like epitaxial diodes: I. The I–V characteristics

A practical quantitative model is presented to account for the I–V characteristics of pin diodes based on epitaxial Ge-like materials. The model can be used to quantify how the different material properties and recombination mechanisms affect the diode performance. The importance of dislocations, non-passivated defects, and residual intrinsic layer doping in determining the qualitative shape of the I–V curves is discussed in detail. Examples are shown covering literature diodes as well as diodes fabricated with the purpose of validating the theoretical effort.

Understanding of complex spin up-conversion processes in charge-transfer-type organic molecules

Despite significant progress made over the past decade in thermally activated delayed fluorescence (TADF) molecules as a material paradigm for enhancing the performance of organic light-emitting diodes, the underlying spin-flip mechanism in these charge-transfer (CT)-type molecular systems remains an enigma, even since its initial report in 2012. While the initial and final electronic states involved in spin-flip between the lowest singlet and lowest triplet excited states are well understood, the exact dynamic processes and the role of intermediate high-lying triplet (T) states are still not fully comprehended. In this context, we propose a comprehensive model to describe the spin-flip processes applicable for a typical CT-type molecule, revealing the origin of the high-lying T state in a partial molecular framework in CT-type molecules. This work provides experimental and theoretical insights into the understanding of intersystem crossing for CT-type molecules, facilitating more precise control over spin-flip rates and thus advancing toward developing the next-generation platform for purely organic luminescent candidates.

Developing Deep Ultraviolet Laser Diode: Design and Improvement of Al0.62Ga0.38N/Al0.68Ga0.32N Quantum Wells on AlN Substrates for 266 nm DUV Emission

A deep ultraviolet (DUV) laser diode is a compact and efficient semiconductor device that emits laser light in the deep ultraviolet range. Its unique properties make it suitable for a wide range of applications in fields such as manufacturing, research, and healthcare. In this research we propose two Al-graded Electron Blocking Layer (EBL) and quantum barriers (QBs) to improve the performance of AlGaN-based Deep UV-LDs. The electrical properties and optical properties of three structures containing conventional EBL, composition graded increased EBL, and liner graded increased of EBL and QBs were numerically investigated. It was found that the structure-C with linear graded increased EBL and QBs significantly improved the Optical Confinement Factor (OCF) 21%, gain 1600 cm-1, emission power 0.060 W, raised the carrier concentration in the MQWs region, enhanced the stimulated recombination rate and reduced the carrier leakage, of the laser diode (LDs). But at a 100-mA injection current, the threshold current and voltage were reduced to 43 mA and 5.00 V, valance barrier height 270 meV respectively. In compare to the conventional structure, introducing a graded design for both EBL and Quantum Barriers (QBs) with increased aluminum content significantly enhanced the performance of the laser diode (LD). This improvement is essential for advancing Deep Ultraviolet Laser Diodes (DUV-LD) technology.

Molecular Structure Effects on Ionic Diode Performance in Desalination: Ultrahigh Rectification in Butylated Intrinsically Microporous Polyamine (PIM‐EA‐TB)

AbstractIonic diodes are components in ionic circuits for AC‐electricity driven desalination and ion extraction processes. Independent of the ionic diode type/mechanism, achieving ionic current rectification at high ionic strengths is challenging but important, for example in seawater desalination and treatment of brine. Here, the butylation of a molecularly rigid (glassy) polymer of intrinsic microporosity (PIM‐EA‐TB) is shown to give anionic diodes with ultrahigh rectification effects (associated with interfacial resistivity) even in high ionic strength aqueous 2 M NaCl solution. The effect is rationalised based on polymer structure affecting ion transport.

Optical injection locking and optical-fiber data transmission by directly modulated wavelength tunable laser transmitters

Enhancement of the small- and large-signal modulation performance of wavelength tunable laser diode (TLD) transmitters under strong optical injection locking (OIL) is investigated numerically in back-to-back and optical-fiber transmission schemes. Our model is based on the spatiotemporal description of laser dynamics as due to the composite cavity design of TLDs, the usual rate equation formalism is not directly applicable. We demonstrate that TLD transmission strongly depends on wavelength tuning, which was investigated over a 21-nm range between 1529 and 1550 nm emission wavelengths. The best performance for both free-running (FR) and OIL TLDs is achieved at shorter wavelengths, 1529 nm for our device. Although in both cases this is due to larger differential material gain at shorter wavelengths, the underlying physics of the effect is completely different. For an FR TLD, it is the resonance oscillation frequency (ROF) that defines the best modulation speed, while for an OIL TLD, the achievable modulation speed depends on the cavity mode shift due to optical injection. Both the ROF and the cavity mode shift increase when the differential gain increases. However, the ROF is the device’s fixed parameter, while the cavity mode shift is defined by the OIL conditions, and thus, it can be optimized. The superior performance of the optical fiber digital data transmission with the OIL TLD is demonstrated at around 20-Gb/s modulation speed for standard fibers. This result is attributed to an enhanced modulation response and suppressed frequency chirping of the OIL TLD, and it is important for practical utilization of TLD transmitters.

Effect of the Filling Liquid Ratio on the Thermal Performance of a Novel Thermal Diode with Wick

Effect of the Filling Liquid Ratio on the Thermal Performance of a Novel Thermal Diode with Wick

Controlling GaN-Based Laser Diode Performance by Variation of the Al Content of an Inserted AlGaN Electron Blocking Layer.

The leakage of the electronic current of a laser diode (LD) has some significant influences on the performance of the LD. In this study, commercial simulation software LASTIP is used to numerically evaluate the performances of LDs by using different wavelengths and Al contents of the electron blocking layer (EBL). These LDs a adopt multilayer structure, which contains cladding layers, waveguide layers, multiple quantum well layers, contact layers and an AlxGa1-xN EBL. The influence mechanism of EBL is theoretically examined by analyzing the simulated performances. It is found that for short-wavelength violet LDs, the electrical and optical properties of the LD will reach the optimum state when the Al content (x) in the EBL is nearly 0.25. For long-wavelength green LDs, it will achieve optimum electrical and optical properties when the Al content in the EBL is as low as possible. We also compare the simulation results of LDs with emission wavelengths in the range of violet and green, including blue cyan, for a more general evaluation. According to the simulated results, it is verified that the influence of the EBL's Al content on LD performance enhances as the wavelength increases.

Boosting the Efficiency of High-Resolution Quantum Dot Light-Emitting Devices Based on Localized Surface Plasmon Resonance.

With pixel miniaturization, the performance of high-resolution quantum dot light-emitting diodes (QLEDs) usually degrades. Considering the dimension of ultrasmall pixels, herein, a barrier architecture based on localized surface plasmon resonance (LSPR) that promotes the radiative recombination of neighboring quantum dots is rationally designed to improve the device performance. Au nanoparticles (NPs) are embedded in an insulating polymer to form a honeycomb-patterned barrier layer via the nanoimprint process. Each pixel fabricated in the void area (average diameter of 1.5 μm) of the barrier layer is surrounded by a number of LSPR-NPs to enhance the luminescence. The resultant green QLEDs with a resolution of 9027 pixels per inch show a maximum external quantum efficiency of 11.1%, a 42.8% enhancement compared to the control device. Additionally, the lifetime of high-resolution QLEDs is obviously improved by the LSPR effect.

Room temperature operation of germanium-silicon single-photon avalanche diode.

The ability to detect single photons has led to the advancement of numerous research fields1-11. Although various types of single-photon detector have been developed12, because of two main factors-that is, (1) the need for operating at cryogenic temperature13,14 and (2) the incompatibility with complementary metal-oxide-semiconductor (CMOS)fabrication processes15,16-so far, to our knowledge, only Si-based single-photon avalanche diode (SPAD)17,18 has gained mainstream success and has been used in consumer electronics. With the growing demand to shift the operation wavelength from near-infrared to short-wavelength infrared (SWIR)for better safety and performance19-21, an alternative solution is required because Si has negligible optical absorption for wavelengths beyond 1 µm. Here we report a CMOS-compatible, high-performing germanium-silicon SPAD operated at room temperature, featuring a noise-equivalent power improvement over the previous Ge-based SPADs22-28 by 2-3.5 orders of magnitude. Key parameters such as dark count rate, single-photon detection probability at 1,310 nm, timing jitter, after-pulsing characteristic time and after-pulsing probability are, respectively, measured as 19 kHz µm-2, 12%, 188 ps, ~90 ns and <1%, with a low breakdown voltage of 10.26 V and a small excess bias of 0.75 V. Three-dimensional point-cloud images are captured with direct time-of-flight technique as proof of concept. This work paves the way towards using single-photon-sensitive SWIR sensors, imagers and photonic integrated circuits in everyday life.

On-Shelf and Operational Decay Dynamics of Self-Healing Quasi-Two-Dimensional Perovskite Light-Emitting Devices.

Currently, the external quantum efficiency (EQE) performance of perovskite light-emitting diodes (PeLEDs) is approaching its theoretical limit. The main drawback of PeLEDs is their stability. Ion migration in the perovskite layer is one of the main causes of the operational decomposition of PeLEDs. Here, we find that butylammonium-based quasi-two-dimensional (quasi-2D) PeLEDs show self-healing ability, revealing the existence of ion migration in the fabricated perovskite layer. Then, on the basis of the analysis of ∼170 operational decay EQE curves, patterns of on-shelf and operational decay in self-healing quasi-2D PeLEDs have been identified. The uneven distributions of resistance on the perovskite film surface are proposed to cause secondary electric fields. The electroluminescent scintillation in certain regions results in fluctuating electroluminescence of PeLEDs, further proving the existence of microcosmic steric ion movement under secondary electric fields. Our work explores the decay patterns of self-healing PeLEDs and highlights the impact of steric ion movements on the decay processes of PeLEDs.

In Situ Hydrolysis of Phosphate Enabling Sky-Blue Perovskite Light-Emitting Diode with EQE Approaching 16.32.

The performance of blue perovskite light-emitting diodes (PeLEDs) lags behind the green and red counterparts owing to high trap density and undesirable red shift of the electroluminescence spectrum under operation conditions. Organic molecular additives were employed as passivators in previous reports. However, most commonly have limited functions, making it challenging to effectively address both efficiency and stability issues simultaneously. Herein, we reported an innovatively dynamic in situ hydrolysis strategy to modulate quasi-2D sky-blue perovskites by the multifunctional passivator phenyl dichlorophosphate that not only passivated the defects but also underwent in situ hydrolysis reaction to stabilize the emission. Moreover, hydrolysis products were beneficial for low-dimensional phase manipulation. Eventually, we obtained high-performance sky-blue PeLEDs with a maximum external quantum efficiency (EQE) of 16.32% and an exceptional luminance of 5740 cd m-2. More importantly, the emission peak of devices located at 485 nm remained stable under different biases. Our work signified the significant advancement toward realizing future applications of PeLEDs.