Novel IR photodetectors and energy harvesting devices

Abstract

For MWIR IR detectors, we designed a meta-surface to enhance QE across 2 to 6 microns. The relative enhancement depends on the intrinsic absorption coefficient, α, of the material. If α is large at 2x104/cm, a 0.1 micron-thick metadetector can have a peak QE of 90%, which is 2.6 times higher than the conventional detector. The improvement is larger at a smaller α. When it is 2000/cm, the improvement is about 10 times with a peak QE of 49%. For energy harvesting devices, we designed several nanostructures etched on top of silicon solar cells to enhance their absorption. Employing an array of nano-columns increases absorption from 55% to 93% at 0.7 microns and from 5.0% to 20% at 1.0 microns. An array of nano-cones further increases the average absorption to 95% between 0.4 to 0.8 microns. The overall integrated absorption is increased by 71% for nano-columns and 91% for nano-cones. For GaAs solar cells, a metasurface can improve photocurrent by 26% from a planar solar cell with a 100 nm-thick absorber.