Indium Nitride: A New Material for High Efficiency, Compact, 1550NM Laser-Based Terahertz Sources in Explosives Detection and Concealed Weapons Imaging

Indium nitride (InN) is identified as a promising terahertz (THz) emitter based on the optical and electronic properties of high quality In- and N-face samples. Time domain THz spectroscopy has been employed to measure the pump wavelength and background carrier concentration dependence of THz emission from InN. There is no discernable difference between the In- and Nface InN samples, as expected for the improved crystalline quality and concomitant low background electron density and high mobility for both polarities. While there is only a weak dependence of THz signal on pump wavelength from 800 nm to 1500 nm, there is a strong dependence on background electron density. Modeling shows that the dominant mechanism for THz generation in bulk InN is the current associated with the diffusion of the photo-generated electrons at elevated electron temperature (photo-Dember effect) and the redistribution of the background electrons under drift, with larger screening from the higher mobility electrons as compared to holes. Compensation or p-type doping in conjunction with manipulation of the large internal electric fields in InN/InGaN nanostructures should lead to significant improvements in THz emitters. Prepared in collaboration with the Materials Department, University of California Santa Barbara, CA and Cornell University, Ithaca, NY. Presented at the Army Science Conference (25th), Transformational Army Science and Technology - Charting the future of S&T for the Soldier, held in Orlando, Florida on 27-30 Nov 2006. Published in proceedings of the same. See also ADM002075, The original document contains color images.