By alloying GaN with AlN the emission of AlGaN light-emitting diodes can be tuned to cover almost the entire ultraviolet spectral range (210–400 nm), making ultraviolet light-emitting diodes perfectly suited to applications across a wide number of fields, whether biological, environmental, industrial or medical. However, technical developments notwithstanding, deep-ultraviolet light-emitting diodes still exhibit relatively low external quantum efficiencies because of properties intrinsic to aluminium-rich group III nitride materials. Here, we review recent progress in the development of AlGaN-based deep-ultraviolet light-emitting devices. We also describe the key obstacles to enhancing their efficiency and how to improve their performance in terms of defect density, carrier-injection efficiency, light extraction efficiency and heat dissipation. This Review covers recent progress in AlGaN-based deep-ultraviolet light-emitting devices. The key technologies of how to improve their performance, carrier-injection efficiency, light extraction efficiency and heat dissipation are discussed.

The emergence and prospects of deep-ultraviolet light-emitting diode technologies

Light-emitting diodes with emission wavelengths less than 400 nm have been developed using the AlInGaN material system. For devices operating at shorter wavelengths, alloy compositions with a greater aluminium content are required. The material properties of these materials lie on the border between conventional semiconductors and insulators, which adds a degree of complexity to the development of efficient light-emitting devices. A number of technical developments have enabled the fabrication of LEDs based on group three nitrides (III-nitrides) that emit in the UV part of the spectrum, providing useful tools for a wealth of applications in optoelectronic systems.

Ultraviolet light-emitting diodes based on group three nitrides

In this paper, recent advances in AlGaN-based deep-ultraviolet (DUV) light-emitting diodes (LEDs) are demonstrated. 220–350-nm-band DUV LEDs have been realized by developing crystal growth techniques for wide-bandgap AlN and AlGaN semiconductors. Significant increases in internal quantum efficiency (IQE) have been achieved for AlGaN DUV emissions by developing low-threading-dislocation-density (TDD) AlN buffer layers grown on sapphire substrates. The electron injection efficiency (EIE) of the LEDs was also significantly increased by introducing a multiquantum barrier (MQB). We also discuss light extraction efficiency (LEE), which is the most important parameter for achieving high-efficiency DUV LEDs. We succeeded in improving LEE by developing a transparent p-AlGaN contact layer. The maximum external quantum efficiency (EQE) obtained was 7% for a 279 nm DUV LED. EQE could be increased by up to several tens of percent through the improvement of LEE by utilizing transparent contact layers and photonic nanostructures in the near future.

https://iopscience.iop.org/article/10.7567/JJAP.53.100209/pdf

Recent progress and future prospects of AlGaN-based high-efficiency deep-ultraviolet light-emitting diodes

Application of GaN-based ultraviolet-C light emitting diodes--UV LEDs--for water disinfection.

The UV-light emitting diode (LED) has been attracting significant attention as a new UV source that can replace conventional mercury gas-filled lamps in water disinfection applications. However, the UV-LED remains a relatively new addition to the water treatment toolbox. The current lack of fundamental understanding risks underutilizing uniquely advantageous features of the UV-LED due to unguided design and non-optimized disinfection practices. Our review presents the necessary fundamental knowledge required for the successful implementation of UV-LEDs, including the mechanism of light generation, LED chip fabrication, package design, and essential properties of UV-LEDs. We introduce distinct advantages, such as wavelength tuning, control of radiation patterns, and array design, while emphasizing the significant differences between LED and mercury lamp technologies required to achieve successful technology transfer. Previous studies investigated the design of UV-LED disinfection systems; however, little consensus has yet emerged regarding the integration of LEDs into flow-through reactors. While UV-LED disinfection systems will undisputedly mature in the near future, environmental engineers face a number of urgent research needs in this area including heat sink design, radiation pattern and array design optimization for uniform UV dose delivery, targeted pathogen-wavelength considerations, improved light extraction, and component monitoring systems.

LED revolution: fundamentals and prospects for UV disinfection applications

Lateral-conduction, substrate-free flip-chip (SFFC) light-emitting diodes (LEDs) with peak emission at 276 nm are demonstrated for the first time. The AlGaN multiple quantum well LED structures were grown by metal?organic chemical vapor deposition (MOCVD) on thick-AlN laterally overgrown on sapphire substrates. To fabricate the SFFC LEDs, a newly-developed laser-assisted ablation process was employed to separate the substrate from the LED chips. The chips had physical dimensions of 1100?900 ?m2, and were comprised of four devices each with a 100?100 ?m2 junction area. Electrical and optical characterization of the devices revealed no noticeable degradation to their performance due to the laser-lift-off process.

https://iopscience.iop.org/article/10.1143/APEX.4.032102/pdf

276 nm Substrate-Free Flip-Chip AlGaN Light-Emitting Diodes

We report 290 nm emission deep ultra-violet light emitting diodes with AlGaN multiple quantum well active regions exhibiting stable cw-powers in excess of 2 mW. For flip-chip packaged devices with an active area of 140 µm2 there was no saturation of the output powers even for DC pump currents up to 60 mA. The light emitting diodes were deposited over 17-µm-thick high-quality pulsed, laterally overgrown AlN layers over sapphire. From the on-wafer measurement of the thermal degradation of output powers, we estimated the lifetimes to be well over 5000 h. The superior performance of the reported light emitting diodes is attributed to reduced thermal impedance and a lower overall defect density in the laterally overgrown AlN.

https://iopscience.iop.org/article/10.1143/JJAP.46.L877/pdf

Robust 290 nm Emission Light Emitting Diodes over Pulsed Laterally Overgrown AlN

We report on room-temperature (RT) operation of a 280 nm deep ultraviolet light emitting diode lamp with monolithic micro-pixel device geometry. RT continuous-wave power as high as 42 mW was measured at a dc pump current of 1 A for a device active area of 880 µm2. For RT operation at a peak dc power of 22 mW (pump current 400 mA), the lamps packaged on TO-66 headers had a 50% power lifetime in excess of 1500 h.

http://iopscience.iop.org/article/10.1143/APEX.2.102101/pdf

280 nm Deep Ultraviolet Light Emitting Diode Lamp with an AlGaN Multiple Quantum Well Active Region

In this paper, we report for the first time, high voltage operations of field plated Al1–xInxN (x≈0.18) HEMTs. The epilayer structure of our devices consisted of AlInN/GaN HEMT structure with and without AlN cap layer. 1.25 μm gate-length AlInN/GaN HEMT devices were then fabricated with 2 μm source-gate distance using our baseline fabrication process. The gate-drain spacing were varied from 6 (baseline) to 12 μm. The devices were field-plated to analyze the breakdown voltage. The maximum drain current density in devices grown on sapphire substrates was around 1.2 A/mm (at a +3 V gate bias). Maximum transconductance was around 370 mS/mm. The insulating AlN cap layer, combined with the field-plated gate design had proved to substantially improve the devices OFF-state breakdown voltage. The measured breakdown voltage was as high as 350-400 V. The results presented highlights the potentials of AlInN-based devices for the high-voltage and energy-efficient power-electronics applications (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

High voltage operation of field-plated AlInN HEMTs

We present a method to determine the average device channel temperature of AlGaN/GaN metal–oxide–semiconductor heterostructure field effect transistors (MOSHFETs) in the time domain under continuous wave (CW) and periodic-pulsed RF (radiation frequency) operational conditions. The temporal profiles of microwave output power densities of GaN MOSHFETs were measured at 2 GHz under such conditions and used for determination of the average channel temperature. The measurement technique in this work is also being utilized to determine the thermal time constant of the devices. Analytical temporal solutions of temperature profile in MOSHFETs are provided to support the method. The analytical solutions can also apply to generic field effect transistors (FETs) with an arbitrary form of time-dependent heat input at the top surface of the wafer. It is found that the average channel temperature of GaN MOSHFETs on a 300 μm sapphire substrate with the output power of 10 W/mm can be over 400 °C in the CW mode while the average channel temperature of GaN MOSHFETs on a SiC substrate with the same thickness only reaches 50 °C under the same condition. The highest average channel temperature in a pulsed RF mode will vary with respect to the duty cycle of the pulse and type of the substrate.

Determination of the average channel temperature of GaN MOSHFETs under continuous wave and periodic-pulsed RF operational conditions

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

Monirul Islam

Author Tools

Chat about Author