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Quantum dot infrared photodetectors have generated significant interest in recent years. They have the potential to outperform quantum well detectors in terms of normal-incidence responsivity and higher operating temperatures. Here, an InGaAs/GaAs dots-in-a-well detector grown by metal-organic chemical vapor deposition is spectrally tuned by rapid thermal annealing under dielectric layers. Four films are considered: SiO2 deposited by both plasma-enhanced chemical vapor deposition and sputter deposition, as well as TiO2 deposited by electron-beam evaporation and sputter deposition. The devices fabricated after these treatments are compared with an uncapped but annealed reference, and also with an as-grown device. The photoresponse peak in the latter occurs at 7.1 μm, whereas the peak responses of the annealed devices range from 7.4 to 11.0 μm. The films themselves were characterized and their properties related to the photoluminescence and spectral photoresponse of each detector. Peak responsivity, specific detectivity, and dark current were also measured for each device to compare their performance.