High Efficiency UV-LEDs Based on Hybrid 2D/3D Materials

The material system of aluminum-gallium-indium-nitride makes very efficient visible light emitters but still inefficient ultraviolet emitters. As a result, the ever-increasing applications of ultraviolet light emitters in healthcare, personal hygiene, and homeland security continue to be fulfilled by conventional sources that are bulky, inefficient, and toxic.

This project will take a new approach; it will combine 3-dimensional (3D) materials based on aluminum-gallium-indium-nitride with 2-dimensional (2D) materials based on boron-nitride to create new hybrid materials. These hybrid materials are expected to reduce internal light emission losses to yield ultraviolet emitters that are more than three times more efficient than the current state-of-the-art.

The proposed research should make it possible to replace conventional emitters with the more efficient, smaller, safer, and more economical emitter. The project will also train graduate students in order to retain US leadership in this technology, it will seek to encourage minority students to pursue science education, and it will generate interest in semiconductor research among undergraduate students and the public.

Technical Description: Ultraviolet light-emitting diodes (UV-LEDs) emitting in the UV-C range (280nm – 220 nm) are widely needed but highly inefficient. The scientific objective of the proposed research is to increase the efficiency of UV-LEDs emitting at 280 nm wavelength by investigating the integration of new materials into LED structures to create the next generation of vertically conducting devices.

For the last two decades, the focus of UV-LED research was mainly to improve the material quality with an aim to increase the external quantum efficiency (EQE). The EQE is the product of internal quantum efficiency (IQE), injection efficiency (IE), and light extraction efficiency (LEE). In a typical 280 nm UV-LED, the IQE and IE are around 80%, whereas the LEE is less than 5% resulting in EQE less than 4%.

The proposed project aims to increase LEE by incorporating hybrids of 2D and 3D materials into the UV-LED structures so as to reduce internal absorptions and reflections. Simulations project that the proposed scheme will dramatically improve the LEE to around 48%. Thus, it should increase the EQE by more than three times relative to the average EQE (~ 10%) of state-of-the-art 280 nm UVLED emitters.

Success in this project will leap the technology forward. The project entails epitaxial growth by metal-organic chemical deposition (MOCVD), device design, processing, and material/device characterizations; it will enhance our understanding and proficiency in these fields. The graduate and undergraduate students involved in the project will become experts in these techniques as they become the next generation of researchers.

This project is jointly funded by the division of Electrical, Communications and Cyber Systems (ECCS), and by the Established Program to Stimulate Competitive Research (EPSCoR).

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.