Jonathan J. Wierer Jr., Lehigh University Center for Photonics and Nanoelectronics, Dept. of Electrical and Computer Engineering
Will present a talk entitled:
“Researching Efficient InGaN LEDs for displays”
Abstract: InGaN emitters have been used successfully in solid-state lighting. Interest has shifted to using them in emissive displays for emerging applications such as virtual/augmented reality viewers. Efficient emitters across the entire visible spectrum are desired to enable these display applications. InGaN-based multiple quantum wells (MQWs) produce the highest efficiency violet-blue light-emitting diodes (LEDs) and laser diodes. Theoretically, increasing the indium composition in InGaN QWs produces longer wavelength emission too, but realizing the same level of efficiencies at longer wavelengths has proven to be difficult. This talk discusses two activities to create efficient III-nitride emitters at green-red wavelengths for displays. First, InGaN LEDs emitting in the green to red using AlGaN interlayer designs are discussed. Incorporating tensile AlGaN interlayers within InGaN-based active layers leads to control of compressive strain, retention of indium within the InGaN, and prevention of defects. These designs have led to some of the highest efficiencies in the green to red. To gauge progress and guide new designs, we have developed methods to determine the underlying recombination rates of the active layers. We have shown that long wavelength AlGaN interlayer designs have defect recombination similar to traditional blue LEDs, while spontaneous rates can be orders of magnitude lower. We have used these methods and findings to produce InGaN-based red LEDs. The second topic is our efforts to create InGaN-based quantum dot active layers. Theoretical calculations on InGaN quantum dots (QDs) show they can overcome nonradiative Auger recombination and create efficient emitters. A new QD synthesis method using photoelectrochemical etching (PEC) is described that produces ensembles of QDs with smaller sizes and in a tighter distribution compared to other methods. These PEC QDs can be used as an alternative active layer to quantum wells or as a growth template layer to control subsequent self-assembled quantum dot growth.
Bio: Dr. Wierer is an Associate Professor at Lehigh University and is jointly appointed in the Center for Photonics and Nanoelectronics and the Department of Electrical and Computer Engineering. His research interests include semiconductor device physics and semiconductor materials science. Specifically, he is interested in researching electronic and optoelectronic devices with III-nitride semiconductors. Prior to joining Lehigh University, Dr. Wierer worked at Philips-Lumileds and Sandia National Labs. At Lumileds Advanced Laboratories his research focused on novel III-nitride light-emitting diodes (LEDs). This includes the development of the first high-power (1 Watt) flip-chip III-nitride LED, and seminal work on III-nitride photonic crystal LEDs. At Sandia National Laboratories his interests broadened into other III-nitride research areas including — solar cells, intersubband devices, layer intermixing, power electronic devices, ultra-violet LEDs, and nanowire LEDs. Most notable is his ground-breaking work on proposing laser diodes as an ultra-efficient light source for solid-state lighting. Dr. Wierer has authored or co-authored over 180 journal publications and conference presentations, and holds 42 patents, predominately related to III-nitride devices. He is an associate editor for the IEEE Photonics Technology Letters journal. He is a senior member of the Institute of Electrical and Electronics Engineers and the Optical Society of America, and a member of the Illumination Engineering Society and the International Society for Optics and Photonics.
Zoom:
Join Zoom Meeting
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Meeting ID: 985 6998 1674
Passcode: 749753
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Wednesday April 21st, 2021
4pm
*Co-Sponsored by IEEE student branch and HKN
