We have investigated a particular class of photovoltaic quantum well intersubband photodetectors. Each period of the active region in these structures consists of four zones, namely an excitation zone, a drift zone, a capture zone, and a tunneling zone. The devices show pronounced photovoltaic behavior and high detectivities. In particular, the responsivity without external bias is substantially enhanced if resonant carrier capture is achieved due to an appropriate design of the capture zone. ©1997 American Institute of Physics.