Upmost efficiency, few-micron-sized midwave infrared HgCdTe photodetectors

Abstract

Resonant cavity-assisted enhancement of optical absorption was a photodetector designing concept emerged about two and half decades ago, which responded to the challenge of thinning the photoactive layer while outperforming the efficiency of the monolithic photodetector. However, for many relevant materials, meeting that challenge with such a design requires unrealistically many layer deposition steps, so that the efficiency at goal hardly becomes attainable because of inevitable fabrication faults. Under this circumstance, we suggest a new approach for designing photodetectors with absorber layer as thin as that in respective resonant cavity enhanced ones, but concurrently, the overall detector thickness being much thinner, and topmost performing. The proposed structures also contain the cavity-absorber arrangement but enclose the cavity by two dielectric one-dimensional grating-on-layer structures with the same grating pitch, instead of the distributed Bragg reflectors typical of the resonant cavity enhancement approach. By design based on the in-house software, the theoretical feasibility of such ∼ 7.0µm − 8.5µm thick structures with ∼ 100% efficiency for a linearly polarized (TE or TM) mid-infrared range radiation is demonstrated. Moreover, the tolerances of the designed structures' performance against the gratings' fabrication errors are tested, and fair manufacturing tolerance while still maintaining high peak efficiency along with a small deviation of its spectral position off initially predefined central-design wavelength is proved. In addition, the electromagnetic fields amplitudes and Poynting verctor over the cavity-absorber area are visualized. As a result, it is inferred that the electromagnetic fields' confinement in the designed structure, which is a key to their upmost efficiency, is two-dimensional combining in-depth vertical resonant-cavity like confinement, with the lateral microcavity like one set by the presence of gratings.

Mid-infrared photodetector spectrometer concept based on ultra-thin all-dielectric metamaterial with azimuth-incidence-angle tuned perfect optical absorption: Design and analysis

“…For simulating the angular polarized absorption spectra of a pixel P, given its coordinates and FPA Euler's angles, we input the results of Eqs. ( 11) and ( 12) into an in-house software, described elsewhere [12][13][14] .…”

“…2, 3, in the proposed, generally multi-MM, FPA setup, both components of the solid angle of irradiating a pixel may vary concurrently due to Eqs. (11,12) by rotating the FPA as a whole, changing the pixel's coordinate, or both.…”

“…7(b) exposes on each excerpted pixel P the corresponding angles θ P , ϕ P calculated due to Eqs. ( 11) and (12). As Eq.…”

“…But nowadays, it apparently becomes partially or completely achievable, with the advent of the concept, design, and fabrication routes of optical microcavities 8 , photonic crystals (PhC) 9 , metasurfaces (MSs) 10 , and metamaterials (MMs) 11 . In particular, one can concurrently bypass the limitations of low photo-absorption and lower bound on the thickness of the photo-absorbing layer, inherent to the monolithic PD designs, with planar-layers resonant-cavity-enhanced (RCE) MMs, and the large overall thicknesses of the IR RCE PDs, with MS embedded MMs 12,13 , for an overview see 14 and citations therein. It has been shown 14 that with very few thin dielectric layers, which enclose an ultra-thin photo-absorbing film and MS atop, one can design diverse MM PDs for the mid-wave infrared (MWIR) range that have ∼ 100% peaky normal-incidence absorption spectra.…”

Integrated Photonic Structure Enhanced Infrared Photodetectors

“…The photonic structures integrated with infrared detection materials are able to increase the effective light–matter interaction length and producing an intensified local field at the infrared detection material while keeping the material in a small volume. [ 13–16 ] Moreover, the photonic structures integrated with infrared detection materials can adjust the light coupling condition to a critical coupling status, where the reflection is zero and all the incident power is absorbed by the system. When anisotropic photonic structures are integrated with infrared detection materials, polarization detection with high extinction ratio can be achieved.…”