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LighTimes: RPI Researchers Demonstrate the Monolithic Integration of an LED and High-Electron-Mobility Transistor on a Gallium Nitride Chip

11 Jun 2013

June 11, 2013…Researchers from the Smart Lighting Engineering Research Center at Rensselaer Polytechnic Institute report having successfully integrated an LED and a power transistor on the same gallium nitride (GaN) chip. RPI asserts that this technology could eventually enable LED technology that is less expensive to manufacture, significantly more efficient. Ultimately, the researchers say that it could allow functionalities and applications far beyond illumination.

RPI notes that today’s LED lighting systems are chips made from gallium nitride (GaN). LEDs require many external components such as inductors, capacitors, silicon interconnects, and wires that must be installed on or integrated into the chip for it to function. RPI contends that the large size of the chip, with all of these necessary components, complicates the design and performance of LED lighting products. Additionally, RPI says that the process of assembling these complex LED lighting systems can be slow, manually intensive, and expensive.

A new study led by T. Paul Chow, professor in the Department of Electrical, Computer, and Systems Engineering (ECSE) at Rensselaer, sought to simplify LED device manufacturing, with fewer assembly steps and less required automation by fabricating some of the electronics on GaN. The researchers propose that LED devices made with monolithically integrated chips will have fewer parts to malfunction, higher energy efficiency and cost effectiveness, and greater lighting design flexibility. The researchers say that this study is the first step in creating what they call a Light Emitting Integrated Circuit or (LEIC)

Chow and the research team grew a GaN LED structure directly on top of a GaN high-electron-mobility transistor (HEMT) structure, using several basic techniques to interconnect the two regions to creating what they say is the first monolithic integration of a HEMT and an LED on the same GaN-based chip. They reported that device, grown on a sapphire substrate demonstrated light output and light density comparable to standard GaN LED devices.

“Just as the integration of many silicon devices in a single chip—integrated circuits—has enabled powerful compact computers and a wide range of smart device technology, the LEIC will play a pivotal role in cost-effective monolithic integration of electronics and LED technology for new smart lighting applications and more efficient LED lighting systems,” Chow said.

“This new study, and the device we have created, is just the tip of the iceberg,” said Smart Lighting ERC Director Robert Karlicek, a co-author of the study and ECSE professor at Rensselaer. “LEICs will result in even higher energy efficiency of LED lighting systems. But what will be even more exciting are the new devices, new applications, and new breakthroughs enabled by LEICs—they will truly usher in the era of smart lighting.”

The study, titled “Monolithic integration of light-emitting diodes and power metal-oxide semiconductor channel high-electron-mobility transistors for light-emitting power integrated circuits in GaN on sapphire substrate,” was published recently in the journal Applied Physics Letters. See the study at: http://dx.doi.org/10.1063/1.4807125.