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(a) Three-dimensional schematic picture of the dual waveband RCE photodetector on a Si platform with two resonant cavity modes designed for near-IR (1.6 μm) and mid-IR (3.7 μm). (b) SEM cross-sectional image of the dual waveband RCE photodetector deposited onto a SiO2/Si substrate. (c) SEM cross-sectional image with higher magnification to show details of the 1.6 μm resonant cavity structure. (d) Schematic picture of the designed structure. All 29 layers are clearly seen in (b) and (c), demonstrating good film thickness control and uniformity. Sharp interfaces between different layers indicate negligible material inter-diffusion occurs since processing temperatures are low (<160 °C).
Reflectance spectra of the dual waveband RCE photodetector obtained by UV-Vis spectroscopy and FTIR measurement (solid line) and TMM simulation (dotted line), showing excellent agreement. The spectra feature two resonant cavity modes which are clearly identified at 1.6 μm and 3.7 μm.
Responsivity spectra (photoconductivity experiment) and optical absorption spectra (TMM simulation) of the 50 nm and 100 nm PbTe absorbing layers for near-IR and mid-IR detection, demonstrating the operation of the nanocrystalline PbTe based dual waveband RCE photodetector. The discontinuity at 2.6 μm is due to independent experiment/simulation for 50 nm (for near-IR) and 100 nm (for mid-IR) PbTe absorbers, respectively.
Summary of measured fractional peak optical absorption values, FWHM, and quality factors for 1.6 μm and 3.7 μm resonant cavity modes.
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