Two p-type compressively strained-layer (PCSL) In x Ga 1− x As/Al y Ga 1− y As (where, x=0.4, 0.2; y=0, 0.15) quantum well infrared photodetectors (QWIPs) grown by MBE on (100) semi-insulating (SI) GaAs substrates have been investigated for 3-5 μm MWIR and 8-14 μm LWIR imaging arrays applications. The In 0.4Ga 0.6As/GaAs PCSL-QWIP utilizing the resonant transport mechanism between the heavy-hole type-I states and the light-hole type-II states shows a broadband double-peak response between 8 and 9 μm range. Using compressive-strain in the InGaAs quantum well, normal incident absorption was greatly enhanced by reducing the heavy-hole effective mass and increasing the density of states in the off-zone center. Maximum responsivities of 93 mA W −1and 30 mA W −1were obtained at peak wavelengths of λ p1 =8.9 μm and λ p3 =5.5 μm, respectively at V b =1.6 V, and detectivity ( D*) at λ p1 =8.9 μm was found to be 4.0×10 9cm−√ Hz/ Wat V b =0.3 V and T=75 K for this QWIP. The In 0.2Ga 0.8As/Al 0.15Ga 0.85As PCSL-QWIP achieves two-color detection with peak wavelengths at 7.4 μm in the LWIR band and 5.5 μm in the MWIR band. This detector is under background limited performance (BLIP) at T=63 K for biases varying from −2.7 V to +3 V. A detectivity ( D*) of 1.06×10 10cm √ Hz/ Wwas obtained at λ p 7.4 μm, V b 1.0 V and T=81 K for this QWIP.