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Schematic diagram of a dual-band SWIR-MWIR back-to-back p-i-n-n-i-p photodiode structure and schematic band alignment of superlattices in two absorption layers. The colored rectangles in the insets represent the forbidden gap of component materials. Dotted lines represent the effective band gaps of superlattices.
Dark current and differential resistance-area product vs. applied bias of the diode at 150 K. SWIR and MWIR arrows represent the operation bias which shows the dominant behavior of each channel.
Quantum efficiency spectrum of the photodiode at 150 K as function of applied bias. The SWIR signal starts to attenuate at 200 mV and the MWIR signal saturated at 300 mV.
Schematic band diagram at zero bias and under dark condition. VS and VM are the built-in voltages of SWIR and MWIR channels, respectively. Ec, Ev, and EF are the conduction band, valence band, and Fermi level at zero bias.
Calculated detectivities of the two channels at 150 K. The MWIR detection operates at 300 mV positive bias. The detectivity calculation uses the equation in the inset, where λ is wavelength, η is QE, J is dark current density, R × A is differential resistance-area product, h, c, and Kb are basic constants.
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