Bottom-Up Formation of III-Nitride Nanowires: Past, Present, and Future for Photonic Devices.

The realization of semiconductor heterostructures marks a significant advancement beyond silicon technology, driving progress in high-performance optoelectronics and photonics, including high-brightness light emitters, optical communication, and quantum technologies. In less than a decade since 1997, nanowires research has expanded into new application-driven areas, highlighting a significant shift toward more challenging and exploratory research avenues. It is therefore essential to reflect on the past motivations for nanowires development, and explore the new opportunities it can enable.

Superior AlGaN/GaN-Based Phototransistors and Arrays with Reconfigurable Triple-Mode Functionalities Enabled by Voltage-Programmed Two-Dimensional Electron Gas for High-Quality Imaging.

High-quality imaging units are indispensable in modern optoelectronic systems for accurate recognition and processing of optical information. To fulfill massive and complex imaging tasks in the digital age, devices with remarkable photoresponsive characteristics and versatile reconfigurable functions on a single-device platform are in demand but remain challenging to fabricate. Herein, an AlGaN/GaN-based double-heterostructure is reported, incorporated with a unique compositionally graded AlGaN structure to generate a channel of polarization-induced two-dimensional electron gas (2DEGs).

Facile Semiconductor p-n Homojunction Nanowires with Strategic p-Type Doping Engineering Combined with Surface Reconstruction for Biosensing Applications.

Photosensors with versatile functionalities have emerged as a cornerstone for breakthroughs in the future optoelectronic systems across a wide range of applications. In particular, emerging photoelectrochemical (PEC)-type devices have recently attracted extensive interest in liquid-based biosensing applications due to their natural electrolyte-assisted operating characteristics. Herein, a PEC-type photosensor was carefully designed and constructed by employing gallium nitride (GaN) p-n homojunction semiconductor nanowires on silicon, with the p-GaN segment strategically doped and then decorated with cobalt-nickel oxide (CoNiO).

Highly Responsive Switchable Broadband DUV-NIR Photodetector and Tunable Emitter Enabled by Uniform and Vertically Grown III-V Nanowire on Silicon Substrate for Integrated Photonics.

Low-dimensional semiconductor nanostructures, particularly in the form of nanowire configurations with large surface-to-volume-ratio, offer intriguing optoelectronic properties for the advancement of integrated photonic technologies. Here, a bias-controlled, superior dual-functional broadband light detecting/emitting diode enabled by constructing the aluminum-gallium-nitride-based nanowire on the silicon-platform is reported. Strikingly, the diode exhibits a stable and high responsivity (R) of over 200 mAW covering an extremely wide operation band under reverse bias conditions, ranging from deep ultraviolet (DUV: 254 nm) to near-infrared (NIR: 1000 nm) spectrum region.

Large-Area Flexible Perovskite Light-Emitting Diodes Enabled by Inkjet Printing.

Metal halide perovskite light-emitting diodes (PeLEDs) are attracting increasing attention due to their potential applications in flat panel lighting and displays. The solution process, large-area fabrication, and flexibility are attractive properties of PeLEDs over traditional inorganic LEDs. However, it is still very challenging to deposit uniform perovskite films on flexible substrates using a blade or slot-die coating, as the flexible substrate is not perfectly flat.

Manipulating Surface Band Bending of III-Nitride Nanowires with Ambipolar Charge-Transfer Characteristics: A Pathway Toward Advanced Photoswitching Logic Gates and Encrypted Optical Communication.

The operational principle of semiconductor devices critically relies on the band structures that ultimately govern their charge-transfer characteristics. Indeed, the precise orchestration of band structure within semiconductor devices, notably at the semiconductor surface and corresponding interface, continues to pose a perennial conundrum. Herein, for the first time, this work reports a novel postepitaxy method: thickness-tunable carbon layer decoration to continuously manipulate the surface band bending of III-nitride semiconductors.

Construction of organic/GaN heterostructures for DUV-to-NIR broadband photodetection.

Herein, a broadband photodetector (BPD) is constructed with consistent and stable detection abilities for deep ultraviolet to near-infrared spectral range. The BPD integrates the GaN template with a hybrid organic semiconductor, PM6:Y6, via the spin-coating process, and is fabricated in the form of asymmetric metal-semiconductor-metal structure. Under an optimal voltage, the device shows consistent photoresponse within 254 to 850 nm, featuring high responsivity (10 to 60 A/W), photo-to-dark-current ratio over 10, and fast response time.

HVHC-ESD-Induced Oxygen Vacancies: An Insight into the Phenomena of Interfacial Interactions of Nanostructure Oxygen Vacancy Sites with Oxygen Ion-Containing Organic Compounds.

The challenging environmental chemical and microbial pollution has always caused issues for human life. This article investigates the detailed mechanism of photodegradation and antimicrobial activity of oxide semiconductors and realizes the interface phenomena of nanostructures with toxins and bacteria. We demonstrate how oxygen vacancies in nanostructures affect photodegradation and antimicrobial behavior.

Investigating various metal contacts for p-type delafossite α-CuGaO to fabricate ultraviolet photodetector.

Delafossite semiconductors have attracted substantial attention in the field of electro-optics owing to their unique properties and availability of p-type materials that are applicable for solar cells, photocatalysts, photodetectors (PDs) and p-type transparent conductive oxides (TCOs). The CuGaO (CGO), as one of the most promising p-type delafossite materials, has appealing electrical and optical properties. In this work, we are able to synthesize CGO with different phases by adopting solid-state reaction route using sputtering followed by heat treatment at different temperatures.

266 nm ultraviolet communication under unknown interference using UVC micro-LED.

Ultraviolet C (UVC) micro light-emitting diode (LED) can achieve symbol communication rate up to 100Msps at distance 40 meters without transmitter-side lens to guarantee certain communication mobility. We consider what we believe to be a new scenario where high speed UV communciation is realized under unknown low-rate interference. The signal amplitude properties are characterized, and the interference intensity is categorized into three cases, namely weak, medium and high interference intensity.

Light-Induced Bipolar Photoresponse with Amplified Photocurrents in an Electrolyte-Assisted Bipolar p-n Junction.

The p-n junction with bipolar characteristics sets the fundamental unit to build electronics while its unique rectification behavior constrains the degree of carrier tunability for expanded functionalities. Herein, a bipolar-junction photoelectrode employed with a gallium nitride (GaN) p-n homojunction nanowire array that operates in electrolyte is reported, demonstrating bipolar photoresponse controlled by different wavelengths of light. Significantly, with rational decoration of a ruthenium oxides (RuO ) layer on nanowires guided by theoretical modeling, the resulting RuO /p-n GaN photoelectrode exhibits unambiguously boosted bipolar photoresponse by an enhancement of 775% and 3000% for positive and negative photocurrents, respectively, compared to the pristine nanowires.

Achieving Record-High Photoelectrochemical Photoresponse Characteristics by Employing CoO Nanoclusters as Hole Charging Layer for Underwater Optical Communication.

The physicochemical properties of a semiconductor surface, especially in low-dimensional nanostructures, determine the electrical and optical behavior of the devices. Thereby, the precise control of surface properties is a prerequisite for not only preserving the intrinsic material quality but also manipulating carrier transport behavior for promoting device characteristics. Here, we report a facile approach to suppress the photocorrosion effect while boosting the photoresponse performance of n-GaN nanowires in a constructed photoelectrochemical-type photodetector by employing CoO nanoclusters as a hole charging layer.

Anisotropic photoresponse behavior of a LaAlO single-crystal-based vacuum-ultraviolet photodetector.

Nowadays, vacuum-ultraviolet (VUV) photodetectors (PDs) have attracted extensive attention owing to their potential applications in space exploration, radiation monitoring, and the semiconductor industry. Benefiting from its intrinsic ultra-wide band-gap, chemical robustness, and low-cost features, LaAlO shows great promise in developing next-generation compact, cheap, and easy-to-fabricate VUV PDs. In this work, we report the unique anisotropic photoresponse behavior of LaAlO single crystals for VUV photodetection applications.

High Performance of Zero-Power-Consumption MOCVD-Grown β-GaO-Based Solar-Blind Photodetectors with Ultralow Dark Current and High-Temperature Functionalities.

In this article, we report on high-performance deep ultraviolet photodetectors (DUV PDs) fabricated on metal-organic chemical vapor deposition (MOCVD)-grown β-GaO heteroepitaxy that exhibit stable operation up to 125 °C. The fabricated DUV PDs exhibit self-powered behavior with an ultralow dark current of 1.75 fA and a very high photo-to-dark-current ratio (PDCR) of the order of 10 at zero bias and >10 at higher biases of 5 and 10 V, which remains almost constant up to 125 °C.

AlGaN Quantum Disk Nanorods with Efficient UV-B Emission Grown on Si(111) Using Molecular Beam Epitaxy.

AlGaN nanorods have attracted increasing amounts of attention for use in ultraviolet (UV) optoelectronic devices. Here, self-assembled AlGaN nanorods with embedding quantum disks (Qdisks) were grown on Si(111) using plasma-assisted molecular beam epitaxy (PA-MBE). The morphology and quantum construction of the nanorods were investigated and well-oriented and nearly defect-free nanorods were shown to have a high density of about 2 × 10 cm.

Observation of polarity-switchable photoconductivity in III-nitride/MoS core-shell nanowires.

III-V semiconductor nanowires are indispensable building blocks for nanoscale electronic and optoelectronic devices. However, solely relying on their intrinsic physical and material properties sometimes limits device functionalities to meet the increasing demands in versatile and complex electronic world. By leveraging the distinctive nature of the one-dimensional geometry and large surface-to-volume ratio of the nanowires, new properties can be attained through monolithic integration of conventional nanowires with other easy-synthesized functional materials.

Development of highly efficient ultraviolet LEDs on hybrid patterned sapphire substrates.

A hybrid patterned sapphire substrate (HPSS) aiming to achieve high-quality Al(Ga)N epilayers for the development of GaN-based ultraviolet light-emitting diodes (UV LEDs) has been prepared. The high-resolution X-ray diffraction measurements reveal that the Al(Ga)N epilayers grown on a HPSS and conventional patterned sapphire substrate (CPSS) have similar structural quality. More importantly, benefiting from the larger refractive index contrast between the patterned silica array and sapphire, the photons can escape from the hybrid substrate with an improved transmittance in the UV band.

Toward efficient long-wavelength III-nitride emitters using a hybrid nucleation layer.

The realization of efficient III-nitride emitters in the green-to-amber region is fundamental to the monolithic integration of multicolor emitters and the development of III-nitride-based full-color high-resolution displays. A hybrid nucleation layer, which includes sputtered AlN and mid-temperature GaN components, was proposed for the development of efficient III-nitride emitters in the green-to-amber region. The mid-temperature GaN component in the hybrid nucleation layer induced the formation of a stacking fault band structure, which effectively relaxed the misfit stress at the GaN/sapphire interface.

Enhanced light extraction of the deep-ultraviolet micro-LED via rational design of chip sidewall.

In this Letter, we perform a comprehensive investigation on the optical characterization of micro-sized deep-ultraviolet (DUV) LEDs (micro-LEDs) emitting below 280 nm, highlighting the light extraction behavior in relation to the design of chip sidewall angle. We found that the micro-LEDs with a smaller inclined chip sidewall angle (∼33) have improved external quantum efficiency (EQE) performance 19% more than that of the micro-LEDs with a larger angle (∼75). Most importantly, the EQE improvement by adopting an inclined sidewall can be more outstanding as the diameter of the LED chip reduces from 40 to 20 .

High-Voltage, High-Current Electrical Switching Discharge Synthesis of ZnO Nanorods: A New Method toward Rapid and Highly Tunable Synthesis of Oxide Semiconductors in Open Air and Water for Optoelectronic Applications.

A novel method of oxide semiconductor nanoparticle synthesis is proposed based on high-voltage, high-current electrical switching discharge (HVHC-ESD). Through a subsecond discharge in the HVHC-ESD method, we successfully synthesized zinc oxide (ZnO) nanorods. Crystallography and optical and electrical analyses approve the high crystal-quality and outstanding optoelectronic characteristics of our synthesized ZnO.

AlGaN-based deep ultraviolet micro-LED emitting at 275 nm.

The investigation of electrical and optical properties of micro-scale AlGaN deep ultraviolet (DUV) light-emitting diodes (LEDs) emitting at ∼275 was carried out, with an emphasis on fabricated devices having a diameter of 300, 200, 100, 50, and 20 µm, respectively. It was revealed that the LED chips with smaller mesa areas deliver considerably higher light output power density; meanwhile, they can sustain a higher current density, which is mainly attributed to the enhanced current spreading uniformity in micro-scale chips. Importantly, when the diameter of LED chips decreases from 300 µm to 20 µm, the peak external quantum efficiency (EQE) increases by 20%, and the EQE peak current density can be boosted from 8.

Self-powered ultraviolet MSM photodetectors with high responsivity enabled by a lateral n/n homojunction from opposite polarity domains.

We report a GaN-based self-powered metal-semiconductor-metal (MSM)-type ultraviolet (UV) photodetector (PD) by employing a "lateral polarity structure (LPS)" grown on the sapphire substrate. An in-plane internal electric field and different Schottky barrier heights at a metal/semiconductor interface lead to efficient carrier separation and self-powered UV detection. A dark current of 6.

Compositionally graded III-nitride alloys: building blocks for efficient ultraviolet optoelectronics and power electronics.

Wide bandgap aluminum gallium nitride (AlGaN) semiconductor alloys have established themselves as the key materials for building ultraviolet (UV) optoelectronic and power electronic devices. However, further improvements to device performance are lagging, largely due to the difficulties in precisely controlling carrier behavior, both carrier generation and carrier transport, within AlGaN-based devices. Fortunately, it has been discovered that instead of using AlGaN layers with fixed Al compositions, by grading the Al composition along the growth direction, it is possible to (1) generate high-density electrons and holes via polarization-induced doping; (2) manipulate carrier transport behavior via energy band modulation, also known as 'band engineering'.