Detector responsivity enhancement from integrating optimized plasmonic structure layers into quantum dot-in-a-well photodetectors is investigated by a finite integration technique-based simulation. It is found that by including a 0.1 µm thick gold hole-array layer onto a backside illuminated photodetector, the peak detector responsivity is enhanced by nearly a factor of 8. A 0.2 µm thick gold disk-array layer improves the peak responsivity by around 15 instead. The calculated enhancement factors show a good agreement with experimental data by Gu et al. [1] and Lee et al. [2] Simulation method and analytical analysis accomplished in this paper provide a generalized approach to design optimal plasmonic structures integrated to various infrared detecting device configurations.high-temperature operation), [3][4][5] with those of quantum well detectors (better sensitivity and control over operating wavelength), and DWELL detectors are approaching MCTs in terms of responsivity and specificdetectivity [6,7] (although DWELL detectors still exhibit worse performance than MCTs).DWELL detector performance can be enhanced by surface plasmons (SPs) caused by the inclusion of a sub-wavelength metallic hole array (SP polaritons: SPPs) or subwavelength metallic nanoparticles (localized SPs: LSPs). [8][9][10][11][12] SPPs are the collective oscillations of electron plasma in the metallic structure, for example, a metallic hole array, excited by electromagnetic (EM) radiation, [13][14][15][16] which can concentrate light at a subwavelength scale beyond the diffraction limit, thereby significantly enhancing the EM field. LSPs confine SPs in the vicinity of sub-wavelength resonators, for example, metallic disks, which also can significantly enhance the EM field near the surface of the resonators, [17] thereby improving the performance of the photodetectors. [18][19][20]