Quantum Efficiency and Crosstalk in Subwavelength HgCdTe Dual Band Infrared Detectors

This work investigates the spectral quantum efficiency and inter-pixel crosstalk of a MWIR-LWIR dual band, HgCdTe-based focal plane array (FPA) photodetector (MWIR and LWIR stand for mid- and long-wavelength infrared bands). Pixels are $\text{10}\,\mu$ m-wide with truncated pyramid geometry and separated by deep trenches. Three-dimensional combined full-wave electromagnetic and electrical simulations in the drift-diffusion approximation allowed to describe the complex, standing-wave-like spectral features resulting from the light interference and diffraction due to the pixels and illuminating beam aperture. The inter-pixel crosstalk for the MWIR operation demonstrated to be very sensitive to the trench depth, in contrast to the LWIR electrooptical response, left almost unchanged. The present work also investigates the causes of performance worsening in the two IR bands when pixel pitch is reduced to $\text{5}\,\mu$ m, hence well below typical LWIR wavelengths and close to the diffraction limited operation.