High Efficiency Micro-pillar UVC Light Emitting Diodes with Transparent AlGaN p-contact Layers
Abstract
There are several military and commercial application systems that require detectors and optical sources in the UVC (sub-300 nm) part of the spectrum. UVC solar-blind detectors are the key component for several DOD threat warning systems. They are also used in monitoring and safety systems for protection against exposure to the harmful UVC radiation. Similarly UVC LEDs are required for several bio-medical applications in sensing and bacterial remediation. They are also required for air-water purification, food dis-infection and polymer curing in high quality printers. AlxGa1-xN multiple quantum well (MQW) UVC LEDs that were initially pioneered by our research group (under an ARO SBIR) have now become an established commercial product. However their output powers (20-50 mW @ 250 mA) and efficiencies (~ 2-5%) are still well below their visible counterparts. For a large scale market penetration, their output powers and efficiencies need to increase several fold. Moreover, to date, there has been very little research work aimed at integrating UVC LEDs and detectors with electronics on the same chip. These Integrated Optoelectronic chips at UVC wavelengths, can offer significant cost and performance benefits over their discrete counterparts. In this proposed work, we plan to use a new selective-area Pulsed Metalorganic Chemical Vapor Deposition (PMOCVD) and fabricate UVC LED with a new truncated cone Micro-pillar design, and transparent p-AlGaN hole-injection layers. Moreover we propose to remove the sapphire substrates using laser liftoff and fabricate Nano-structures on AlN buffer layers to increase the light extraction efficiency (LEE). These innovations we believe can potentially increase the output power and external quantum efficiency (EQE) by a factor of 3-6. The dependence of UVC light output and EQE will be studied as a function of micro-pillar sizes ranging from 10 µm diameter down to 2 µm. The use of a new selective area growth (SAG) approach, that was developed by our group for Ultra-wide bandgap (UWBG) high-Al AlxGa1-xN Electronics, will enable us to show that in-principle UVC LEDs and Detectors can be monolithically integrated with AlxGa1-xN based transistor electronics. The technology and the high-efficiency devices from this program can play a significant role in maintaining US superiority in the important application areas such as bio-chemical detection, non-line of sight (NLOS) data communications, air-water and food disinfection and polymer curing.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jun 17, 2019
- Source ID
- W911NF1810029
Entities
People
- Asif Khan
Organizations
- Army Contracting Command
- United States Army
- University of South Carolina