A research team at the King Abdullah University of Science and Technology (KAUST) announced their achievement in manufacturing InGaN red LEDS with a peak wavelength of 665nm as well as improved light output power and external quantum efficacy. Their achievement is believed to support more efficient process of full color Micro LED display development.

(Image: KAUST)

One of the challenges of Micro LED display is producing red LEDs with GaN, which is considered almost impossible, according to Kazuhiro Ohkawa, leader of the research group. Red color on Micro LED display is usually made by color conversion or base on different materials and with more defect. Replacing a large portion of the gallium with the element indium can also give the desired red, but it is hard to do because indium easily evaporates from the crystal.

However, the KAUST team has succeed in developing a crystal growth system to realize pure red LEDs. They created a reactor with extra indium vapor above the crystal's surface, a process known as metalorganic vapor-phase deposition. This added pressure prevents the indium in the crystal from escaping. "This gives us a higher indium concentration at the surface," said Ohkawa.

(Image: KAUST)

The team also added aluminum, which has small atoms, to reduce the strain on the crystal for lower down crystal defects that created by Indium, improving the quality of output light. In addition, the red LEDs can operate at 3.3V, only about half comparing to other red LEDs.

The result was published in Applied Physics Express in February 2020.