Simulation Study of Rectifying Antenna Structure for Infrared Wave Energy Harvesting Applications Xi Shao 1,2 , N. Goldsman 1,2 , N. Dhar 3 , F. Yesilkoy 1 , A. Akturk 1,2 , S. Potbhare 1,2 , M. Peckerar 1 1. Department of Electrical and Computer Engineering, University of Maryland, College Park, MD 20742, USA, xshao@umd.edu 2. CoolCAD Electronics LLC, 5000 College Ave. College Park, MD 20740, USA 3. Defense Advanced Research Projects Agency, Microsystems Technology Office, Arlington, VA 2220 Abstract— We present an integrated modeling of an infrared energy harvesting rectenna, which is the integrated combination of a micron size antenna and a nano-scale tunneling diode. The computational model consists of a 2D electrical potential solver in polar coordinate with adaptive gridding to ensure the finest resolution around the antenna tip and a transmission matrix- based Schrodinger equation solver for calculating the electron tunneling probability through the junction. The numerical model enables us to study the rectifying nature of the rectenna and performed scaling analysis of the electron emission from rectifying antenna structure. Keywords-infrared energy harvesting; tunneling diode; rectifying antenna I. INTRODUCTION There are several major radiation sources having wavelengths in the infrared range on the surface of Earth: direct solar radiation and heat-bodies. The solar radiation in these infrared spectra can amount to ~100 W/m 2 . Another major source of infrared radiation on the surface of the Earth is the heat- bodies, e.g. human bodies of temperature around 300 K, Earth’s ground and other heat sources with high temperature. These heat-bodies emit significant amount of infrared radiation, e.g. with peak radiation at wavelengths 9.6 um for objects with temperature 300 K. On the other hand, existing solar cell materials can absorb radiation with wavelengths upto 1.2 um in a relatively efficient way (with efficiency 10- 18%). But, there are no existing efficient ways to harvest infrared radiation for wavelengths from 1.25 um to 10 um. Recently a number of developments in nano-antenna design and fabrication [1] have taken place. These developments are of industrial significance and motivate us to develop models to investigate a promising infrared energy-harvester structure: rectenna. A rectenna is formed with a thin layer of metallic triangle with a sharp tip placed next to a layer of metallic rectangle on top of a substrate. The rectenna is designed to harvest energy by rectifying infrared electromagnetic wave through tunneling diode structure formed with the metallic tip- rectangle junction. The sharp tip of the triangle patch will focus and enhance the electric field under radiation so that it is high enough to enable electrons to tunnel through the junction [2]. To quantify the performance of rectenna energy harvester, we developed an integrated modeling tool to solve for electric potential field distribution around the tip-rectangle junction and use the spatial electric field configuration to feed to Schrodinger equation solver to calculate electric field emission under forward and reverse-bias configurations. The model enables us to quantitatively evaluate the dependence of the electron emission efficiency on the various designs of the rectenna such as antenna tip sharpness, gap distances, etc. II. SIMULATION MODEL A. Simulation Geomatry The rectenna structure is modeled in polar coordinates. Fig. 1 shows the zoom-in view of grid configuration in which grids with radially adaptive gridding are employed to ensure the finest resolution around the metal tip. The simulation domain spans from 0     to 0    azimuthally and the azimuthal boundary is located at 0     with the angular span of the sharp tip being 2 0  . The metallic nature of the sharp tip is prescribed as the boundary condition at 0     in the simulation. In total, 300 uniformly-spaced grids are used azimuthally and 400 non-uniformly-spaced grids are used radially with the finest resolution = 0.1 nm around the tip. Fig. 1: Structure of rectenna and zoom-in view of simulation grid configuration. SISPAD 2012, September 5-7, 2012, Denver, CO, USA SISPAD 2012 - http://www.sispad.org 249 ISBN 978-0-615-71756-2