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US researchers to enlarge the move, or can make LED to zero light failure?

May 04, 2017

University of Illinois at Urbana-Champaign researchers have developed a new approach to enhance the green LED brightness and improve its efficiency.


Professor Can Bayram, assistant professor of electrical and computer engineering at the University of Illinois, has developed a new approach to enhance the brightness and efficiency of green LEDs. (All Source: University of Illinois)

Using industry-standard semiconductor long crystal technology, researchers fabricated gallium nitride (GaN) crystals on silicon substrates that produce high-power green light for solid-state lighting.

"This is a groundbreaking process in which researchers succeed in producing new raw materials on an adjustable CMOS silicon process, which is a square gallium nitride (cubic GaN)," said Can Bayram, assistant professor of electrical and computer engineering at the University of Illinois. ), This material is mainly used for green wavelength emitter.

The use of semiconductors for sensing and communication to open visible light communications applications, and optical communication is the technology to completely change the light application. LEDs that support CMOS processes can achieve fast, efficient, low-power, and multi-application green LEDs while eliminating the cost of many process devices.

Usually GaN forms one or two crystal structures, hexagonal or cube. Hexagonal GaN is thermally stable and is a traditional semiconductor application. However, hexagonal GaN is more prone to polarization phenomenon, the internal electric field will be negative electrons and positrons separated to prevent them from bonding, resulting in light output efficiency.

So far, researchers can only use the molecular beam epitaxy (Molecular beam epitaxy) to create square GaN, this process is very expensive and compared with the MOCVD process is very time-consuming.

Researchers have succeeded in producing new raw materials on the tunable CMOS silicon process, which is square gallium nitride, which is primarily used for green wavelength emitter.

Bayram said: "lithography and isotropic etching techniques create U-row grooves on silicon. This layer of non-conductive barrier plays a key role in shaping hexagonal to square. Our GaN is not internal The electric field can separate the electrons, so there may be overlapping problems, electrons and holes are more quickly combined and made of light.

Bayram and Liu believe that their square GaN crystals may succeed in allowing the LED to reach a zero drop (droop). For green, blue, or UV LEDs, the luminous efficiency of these LEDs will gradually decline with the input of current, the so-called light failure.

This study shows that polarization plays a decisive role in the problem of light failure, pushing electrons away from grooves, especially in low input currents. In the case of zero polarization, the square LED can achieve a thicker light-emitting layer and solve the reduced electron and groove overlap and current overload.


Better green LED will successfully open new LED solid-state lighting applications. For example, these LEDs will emit white light by mixing and achieve energy savings. Other advanced applications also include the use of non-fluorescent green LED manufacturing super-parallel LED applications, water communication and, for example, optical genetics and migraine and other biotechnology applications.


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