Nav: Home

Understanding high efficiency of deep ultraviolet LEDs

February 22, 2019

Deep ultraviolet light-emitting diodes (DUV-LEDs) made from aluminium gallium nitride (AlGaN) efficiently transfer electrical energy to optical energy due to the growth of one of its bottom layers in a step-like fashion. This finding, published in the journal Applied Physics Letters, can lead to the development of even more efficient LEDs.

AlGaN-based DUV-LEDs are receiving much research attention due to their potential use in sterilization, water purification, phototherapy, and sunlight-independent high-speed optical communication. Scientists are investigating ways to improve their efficiency in converting electrical energy into optical energy.

Kazunobu Kojima of Tohoku University specializes in quantum optoelectronics, which studies the quantum effects of light on solid-state semiconductor materials. He and colleagues in Japan used a variety of specialized microscopic techniques to understand how the structure of AlGaN-based LEDs affects their efficiency.

They fabricated an AlGaN-based LED by growing a layer of aluminium nitride on top of a sapphire substrate with a very small one degree off-angle. Next, they grew a cladding layer of AlGaN with silicon impurities on top of the aluminium nitride layer. Three AlGaN 'quantum wells' were then grown on top of this. Quantum wells are very thin layers that confine subatomic particles called electrons and holes within the dimension that is perpendicular to the layers' surface, without restricting their movement in the other dimensions. The top quantum well was finally covered with an electron-blocking layer formed of aluminium nitride and AlGaN with magnesium impurities.

The microscopic investigations revealed that terraced steps form between the bottom aluminium nitride and AlGaN layers. These steps affect the shapes of the quantum well layers above them. Gallium-rich stripes form that connect the bottom steps to the small distortions they cause in the upper quantum well layers. These stripes represent micropaths of electric current in the AlGaN cladding layer. These micropaths, together with a strong localization of movement of electrons and holes within the quantum well layers, appears to increase the LEDs' efficiency in converting electrical energy to optical energy, the researchers say.

The team next plans to use this information to fabricate more efficient AlGaN-based deep ultraviolet LEDs, says Kojima.

Tohoku University

Related Quantum Articles:

Quantum nanoscope
Researchers have studied how light can be used to 'see' the quantum nature of an electronic material.
'Quantum leap' for Liverpool
Physicists from the University of Liverpool have made a huge step forwards towards building a novel experiment to probe the 'dark contents' of the vacuum.
Testing quantum field theory in a quantum simulator
Quantum field theories are often hard to verify in experiments.
Quantum reservoir for microwaves
EPFL researchers use a mechanical micrometer-size drum cooled close to the quantum ground state to amplify microwaves in a superconducting circuit.
Looking for the quantum frontier
Researchers have developed a new theoretical framework to identify computations that occupy the 'quantum frontier' -- the boundary at which problems become impossible for today's computers and can only be solved by a quantum computer.
Quantum mechanics are complex enough, for now...
Physicists have searched for deviations from standard quantum mechanics, testing whether quantum mechanics requires a more complex set of mathematical rules.
Seeing the quantum future... literally
Sydney scientists have demonstrated the ability to 'see' the future of quantum systems and used that knowledge to preempt their demise, in a major achievement that could help bring the strange and powerful world of quantum technology closer to reality.
The sound of quantum vacuum
Quantum mechanics dictates sensitivity limits in the measurements of displacement, velocity and acceleration.
New quantum states for better quantum memories
How can quantum information be stored as long as possible?
Watching quantum jumps
When a quantum system changes its state, this is called a quantum jump.

Related Quantum Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Digital Manipulation
Technology has reshaped our lives in amazing ways. But at what cost? This hour, TED speakers reveal how what we see, read, believe — even how we vote — can be manipulated by the technology we use. Guests include journalist Carole Cadwalladr, consumer advocate Finn Myrstad, writer and marketing professor Scott Galloway, behavioral designer Nir Eyal, and computer graphics researcher Doug Roble.
Now Playing: Science for the People

#529 Do You Really Want to Find Out Who's Your Daddy?
At least some of you by now have probably spit into a tube and mailed it off to find out who your closest relatives are, where you might be from, and what terrible diseases might await you. But what exactly did you find out? And what did you give away? In this live panel at Awesome Con we bring in science writer Tina Saey to talk about all her DNA testing, and bioethicist Debra Mathews, to determine whether Tina should have done it at all. Related links: What FamilyTreeDNA sharing genetic data with police means for you Crime solvers embraced...