A voltage‐controlled tunable two‐color infrared detector with photovoltaic (PV) and photoconductive (PC) dual‐mode operation at 3–5 &mgr;m and 8–14 &mgr;m using GaAs/AlAs/AlGaAs double barrier quantum wells (DBQWs) and bound‐to‐continuum GaAs/AlGaAs quantum wells is demonstrated. The photoresponse peak of the photovoltaic GaAs/AlAs/GaAlAs DBQWs is at 5.3 &mgr;m, and that of the photoconductive GaAs/GaAlAs quantum wells is at 9.0 &mgr;m. When the two‐color detector is under a zero bias, the spectral response at 5.3 &mgr;m is close to saturate and the peak detectivity at 80 K can reach 1.0×1011cmHz1/2/W, while the spectral photoresponsivity at 9.0 &mgr;m is absolutely zero completely. When the external voltage of the two‐color detector is changed to 2.0 V, the spectral photoresponsivity at 5.3 &mgr;m becomes zero while the spectral photoresponsivity at 9.0 &mgr;m increases comparable to that at 5.3 &mgr;m under zero bias, and the peak detectivity (9.0 &mgr;m) at 80 K can reach 1.5×1010cmHz1/2/W. Strictly speaking, this is a real bias‐controlled tunable two‐color infrared photodetector. We have proposed a model based on the PV and PC dual‐mode operation of stacked two‐color QWIPs and the effects of tunneling resonance with narrow energy width of photoexcited electrons in DBQWs, which can explain qualitatively the voltage‐controlled tunable behavior of the photoresponse of the two‐color infrared photodetector. ©1996 American Institute of Physics.