Researchers at the university of Illinois at urbana-champaign have developed a new way to increase the brightness and efficiency of green leds
(all images: university of Illinois)
Using industry-standard semiconductor crystal growth technology, researchers fabricated gallium nitride (GaN) crystals on silicon substrates that produce high-power green light for solid-state lighting.
Can Bayram, an assistant professor of electrical and computer engineering at the University of Illinois, said: "This is a breakthrough process. Researchers have succeeded in producing new materials on a tunable CMOS silicon process, namely cubic GaN. ), this material is mainly used for green wavelength emitters."
The use of semiconductors for sensing and communication enables the opening of visible light communication applications, and optical communication is the technology that revolutionizes optical applications. CMOS-enabled LEDs enable fast, high-efficiency, low-power, multi-application green LEDs while saving the cost of many process devices.
Typically GaN forms one or two crystal structures, hexagonal or cubic. Hexagonal GaN is thermally stable and is a traditional semiconductor application. However, hexagonal GaN is more prone to polarization, and the internal electric field separates the negative electrons from the positrons, preventing them from being combined, thus causing a decrease in light output efficiency.
So far, researchers have been able to fabricate square GaN using Molecular beam epitaxy, which is very expensive and time consuming compared to MOCVD processes.
Researchers have succeeded in producing new materials on a tunable CMOS silicon process, namely cubic GaN, which is used primarily for green wavelength emitters.
Bayram said: "lithography and isotropic etching technology make U-line grooves on silicon. This layer of non-conductive resistors plays a key role in shaping hexagons to squares. Our GaN has no internals. The electric field can separate the electrons, so overlapping problems can occur, and electrons and pits combine and make light more quickly."
Bayram and Liu believe that their square GaN crystals could successfully achieve LEDs with zero droop. For green, blue or UVLEDs, the luminous efficiency of these LEDs will gradually decline with the input of current, which is called light decay.
This study shows that polarization plays a pivotal role in the problem of light decay, pushing electrons away from the groove, especially at low input currents. In the case of zero polarization, square LEDs can achieve a thicker luminescent layer and address reduced electron and groove overlap and current overload.
A better-performing green LED will successfully open a new LED solid-state lighting application. For example, these LEDs will be able to emit white light by color mixing and achieve energy savings. Other advanced applications include the use of non-fluorescent green LEDs for the manufacture of ultra-parallel LEDs, underwater communications, and biotechnology applications such as optogenetics and migraine.