Steps that form during LED fabrication improve their efficiency by creating tiny paths of electric current
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.
Kazunobu Kojima | EurekAlert!
Further reports about: > Applied Physics > Applied Physics Letters > Electrons > LEDs > electrical energy > gallium nitride > light-emitting diodes > microscopic > optical communication > quantum effects > quantum wells > semiconductor materials > subatomic particles > ultraviolet > water purification
Shock-dissipating fractal cubes could forge high-tech armor
08.07.2020 | DOE/Los Alamos National Laboratory
Atomic 'Swiss army knife' precisely measures materials for quantum computers
08.07.2020 | National Institute of Standards and Technology (NIST)
Kiel physics team observed extremely fast electronic changes in real time in a special material class
In physics, they are currently the subject of intensive research; in electronics, they could enable completely new functions. So-called topological materials...
Solar cells based on perovskite compounds could soon make electricity generation from sunlight even more efficient and cheaper. The laboratory efficiency of these perovskite solar cells already exceeds that of the well-known silicon solar cells. An international team led by Stefan Weber from the Max Planck Institute for Polymer Research (MPI-P) in Mainz has found microscopic structures in perovskite crystals that can guide the charge transport in the solar cell. Clever alignment of these "electron highways" could make perovskite solar cells even more powerful.
Solar cells convert sunlight into electricity. During this process, the electrons of the material inside the cell absorb the energy of the light....
Empa researchers have succeeded in applying aerogels to microelectronics: Aerogels based on cellulose nanofibers can effectively shield electromagnetic radiation over a wide frequency range – and they are unrivalled in terms of weight.
Electric motors and electronic devices generate electromagnetic fields that sometimes have to be shielded in order not to affect neighboring electronic...
A promising operating mode for the plasma of a future power plant has been developed at the ASDEX Upgrade fusion device at Max Planck Institute for Plasma...
Live event – July 1, 2020 - 11:00 to 11:45 (CET)
"Automation in Aerospace Industry @ Fraunhofer IFAM"
The Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM l Stade is presenting its forward-looking R&D portfolio for the first time at...
07.07.2020 | Event News
02.07.2020 | Event News
19.05.2020 | Event News
09.07.2020 | Medical Engineering
09.07.2020 | Information Technology
09.07.2020 | Life Sciences