Program
Optical Science and Engineering
College
Interdisciplinary
Student Level
Doctoral
Location
PAÍS Building
Start Date
10-11-2022 11:00 AM
End Date
10-11-2022 1:00 PM
Abstract
Light-emitting diodes (LEDs) are by far the most efficient and customizable light source commercially available. While large-area LEDs already have a wide range of uses and represent a massive decrease in energy costs and consumption compared to conventional light sources, applications such as directional lighting, digital displays, and visible light communication would benefit from a reduction in LED source size. Smaller light sources can achieve higher precision directionality, higher display resolution, and faster modulation. Micro-LEDs, usually defined as having a diameter of 50 μm or less, therefore have the potential to further reduce energy consumption and increase functionality. However, micro-LEDs currently suffer from a rapid drop in efficiency with decreasing diameter. While there are several factors that contribute to this size-dependent droop, the focus of our research has been characterizing and mitigating the detrimental effects of surface recombination due to sidewall damage during fabrication. Since the surface-area-to-volume ratio must increase as the diameter of the device decreases, any surface effects will more strongly affect small-area LEDs. To explore how surface recombination affects device operation, we have fabricated micro-LEDs with varying offsets and diameters, and treated a portion of our devices with KOH, which reduces sidewall damage induced during etching. By combining small-signal RF measurements with conventional DC testing, we are then able to extract the micro-LED carrier dynamics, and relate the results to efficiency loss and the effectiveness of sidewall damage removal.
An examination of InGaN micro-LED carrier dynamics through small signal RF analysis
PAÍS Building
Light-emitting diodes (LEDs) are by far the most efficient and customizable light source commercially available. While large-area LEDs already have a wide range of uses and represent a massive decrease in energy costs and consumption compared to conventional light sources, applications such as directional lighting, digital displays, and visible light communication would benefit from a reduction in LED source size. Smaller light sources can achieve higher precision directionality, higher display resolution, and faster modulation. Micro-LEDs, usually defined as having a diameter of 50 μm or less, therefore have the potential to further reduce energy consumption and increase functionality. However, micro-LEDs currently suffer from a rapid drop in efficiency with decreasing diameter. While there are several factors that contribute to this size-dependent droop, the focus of our research has been characterizing and mitigating the detrimental effects of surface recombination due to sidewall damage during fabrication. Since the surface-area-to-volume ratio must increase as the diameter of the device decreases, any surface effects will more strongly affect small-area LEDs. To explore how surface recombination affects device operation, we have fabricated micro-LEDs with varying offsets and diameters, and treated a portion of our devices with KOH, which reduces sidewall damage induced during etching. By combining small-signal RF measurements with conventional DC testing, we are then able to extract the micro-LED carrier dynamics, and relate the results to efficiency loss and the effectiveness of sidewall damage removal.
