Karan Mehta was chosen for the Best Student Poster Award at the 11th International Symposium on Semiconductor Light Emitting Devices (ISSLED 2017), held on October 8-12 in Banff, Canada.

Mehta is a graduate student in the Georgia Tech School of Electrical and Computer Engineering (ECE), where he works in the Computational Electronics and Photonics Research Group headed by ECE Associate Professor Douglas Yoder.

Mehta’s poster was titled “High Reflectivity Ultraviolet AlGaN/Metal Hybrid Distributed Bragg Reflectors” and was co-authored by the students and faculty of the Center for Compound Semiconductors. This work is part of their effort towards realizing ultraviolet VCSELs made of III-Nitride materials.

Obtaining a highly reflective (>99%) bottom (n-side) mirror poses the greatest challenge to the successful demonstration of UV VCSELs. The proposed solution involves leveraging heavy doping and near-bandgap excitonic resonances to enhance the refractive index contrast in each layer pair of an epitaxial DBR situated above a planar metallic mirror, boosting reflectivity and reducing total strain and thermal resistance.   

This research was done as a part of DARPA’s ACES program to develop chip scale atomic clocks (CSACs), requiring a VCSEL operating at a wavelength of 370 nm.