CAREER: Towards highly efficient UV emitters with lattice engineered substrates

The objective of this CAREER project is to significantly improve the efficiency of light emitting diodes in the ultraviolet range, especially in those ranges where incumbent methods show an abrupt drop in efficiency. A new class of flexible materials will be used that will help improve strain related issues faced by this class of ultraviolet emitters, and these materials will also direct light in a specific direction to efficiently extract light out of the device.

A combination of experimental and theoretical investigations will be employed to demonstrate light extraction, material, and device level improvements all resulting in up to 10x improvement over current solutions. The developed structures will not only enhance the capabilities of currently available products but will also enable completely new applications in the field of medical science – skin disease treatments and cardiovascular/eye surgeries, agriculture – food storage and farming, sanitization- air, surface and water; energy savings from efficient devices resulting in sustainability and finally improve reliability of security systems used in banks and for ID cards.

The broader impacts activities will involve assessing the impact of proposed research and large-scale adoption of ultraviolet emitters over incumbent mercury lamps on various fields such as biodiversity, medicine and food security. Incorporation of a module on ”semiconductors are fun” in high school curriculum is proposed by leveraging the research experience for teachers program to introduce semiconductors and their societal impacts early on in the education system.

Different kinds of workforce trainings at various levels – precollege, undergraduate and graduate level are proposed to fill the national level workforce shortage demand owing to the encouraging CHIPS Act related initiatives. Community engagement activities are planned with farming communities to generate awareness about ultraviolet emitters and how they can enhance national food security.

Technical description: This CAREER project aims to address the gap in external quantum efficiency of III- nitride solid state emitters in the ultraviolet emission wavelength range of 280-365 nm to enable a new regime of high-power ultraviolet light emitting diodes. There is a sharp wavelength dependence on the efficiency of devices in this wavelength range, that will be decoupled by the proposed solution.

The research approach will involve the development of mechanically compliant and reflective substrates based on porous semiconductors, to redefine the critical thickness metrics used to design group III-nitride based device epitaxial structures to achieve a projected efficiency improvement by an order of magnitude. Using novel quantum well and carrier injection layers, new methods of synthesis of porous materials, and implementation of semiconductor reflectors will be employed.

Mechanical, optical and opto-electrical computational models will be developed to guide experimental explorations and enhance the understanding of the mechanics and physics of the epitaxial structures being used.

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.