Mid-Infrared Plasmonic Platform based on Heavily Doped Epitaxial Ge-on-Si: Retrieving the Optical Constants of Thin Ge Epilayers

摘要

The n-type Ge-on-Si epitaxial material platform enables a novel paradigm forplasmonics in the mid-infrared, prompting the future development oflab-on-a-chip and subwavelength vibrational spectroscopic sensors. In order toexploit this material, through proper electrodynamic design, it is mandatory toretrieve the dielectric constants of the thin Ge epilayers with high precisiondue to the difference from bulk Ge crystals. Here we discuss the procedure wehave employed to extract the real and imaginary part of the dielectricconstants from normal incidence reflectance measurements, by combining thestandard multilayer fitting procedure based on the Drude model withKramers-Kronig transformations of absolute reflectance data in thezero-transmission range of the thin film.