The first successful demonstration of long‐wavelength infrared (LWIR) detection with a Kastalsky‐type AlGaAs/GaAs superlattice structure is reported. The experimental response band of the detector is centered near 10 &mgr;m in very good agreement with the theoretical response band provided that electron‐electron interactions are taken into account. The detector operates at significantly lower bias voltage than photoconductive multiple quantum well LWIR detectors. This could lead to important advantages in applications to photovoltaic detector arrays. The response at 83 K is about 50% of the response at 24 K. Optimization of the response, operating temperature, or bias voltage has not been carried out.