Ten-stacked InAs/GaAs quantum-dot infrared photodetector with two Al0.1Ga0.9As blocking layers at both sides of the structure is investigated. High responsivity 1.73 A/W under low applied voltage of -1.4 V is observed at 20 K with peak wavelength ∼ 7.6 μ m. The appearance of 3-6 μ m photovoltaic response at higher temperature is attributed to the enhancement of E-1-E-2 and E-2-tunneling transition with increasing temperature. Higher photocurrent avalanche process under negative bias is due to the front blocking layer barrier lowering which results from strain-induced dislocations. © 2005 Published by Elsevier B.V.