All-dielectric grating-assisted absorption enhancement in a subwavelength mercury cadmium telluride layer for infrared photodetectors

Light absorption enhancement in a 1.5 mu m thick mercury-cadmium-telluride (Hg0.762Cd0.238Te, MCT) layer at room temperature utilizing 1D dielectric grating at mid-wave infrared (MWIR) wavelengths (3-5 mu m) has been theoretically investigated. The optimized dielectric grating facilitates light diffraction and scattering into the MCT-absorbing waveguiding layer resulting in an increased lateral optical path. The light absorption was improved from similar to 37.5% to similar to 71% (TE) and similar to 70% (TM) at normal incidence. With enhanced absorption, the photocarrier generation rate in the thin layer would be comparable to a bulk 5 mu m thick MCT layer. A similar to 3x reduction in the MCT layer thickness without compromising absorption has the potential for realizing infrared photodetectors with improved sensitivity at conventional operating temperatures and/or elevated operating temperatures.