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We have tried to improve the responsivity of germanium-based thin-film photodetectors. It has been shown that applying a mechanical strain to the detector led to a 46.6% enhancement on the 1550 nm detection. This improvement is better than the 1310 nm case, because the bandgap shrinkage is more beneficial to the small-energy photon detection. The AuNP coating is even more attractive for responsivity enhancement of thin-film germanium (Ge) detectors. The responsivity enhancement due to the AuNP deposition is as high as 89% and 47%, for the 1310 nm and 1550 nm detections, respectively. To the best of our knowledge, this is the best responsivity enhancement for the thin-film Ge detectors reported to date.