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Abstract GeSn photodetectors monolithically grown on Ge virtual substrates demonstrate mid‐wave infrared (MWIR) detection at room temperature. The lattice mismatch between GeSn and Ge causes dislocations and compressive strain, creating leakage pathways and unwanted indirect band transitions. Designed thin Ge_0.91Sn_0.09triple‐step buffer layers of ≈175 nm total thickness reduce dislocations and enable full relaxation, showing 100% lattice relaxation and smooth surface roughness of 0.83 nm with shorter auto‐correlation length in surface morphology compared to single‐step buffers. Ge_1‐xSn_xphotodetectors (x= 0.09, 0.12, and 0.15) on triple‐step buffers withn‐i‐pconfigurations achieve lattice strain relaxations of 99%, 88%, and 80%, respectively. Ge_0.91Sn_0.09and Ge_0.88Sn_0.12show gradual variation in auto‐correlation amplitude, while Ge_0.85Sn_0.15shows an increase due to lattice mismatch. Shockley–Read–Hall recombination current dominates at low reverse bias due to mismatch‐induced dislocations, while band‐to‐band tunneling current dominates at higher reverse bias due to narrowing bandgap under strong electric fields. The photodetectors show extended spectral response with increasing Sn composition ofi‐GeSn active layer sandwiched by barriers. Ge_0.88Sn_0.12and Ge_0.85Sn_0.15exhibit extended wavelength cut‐offs of 3.12 and 3.27 µm at room temperature, demonstrating significant potential for silicon‐based MWIR applications.