We present new experimental results in the photoresponse behavior of GaAs‐AlAs‐GaAs heterostructures. Structures consisted of a layer of AlAs several thousand angstroms thick, sandwiched between layers of GaAs which were several microns thick. The layer of GaAs nearest the surface was doped degeneratelyntype, whereas, the layer beneath the AlAs was doped nondegeneratelyntype. The asymmetric doping and the AlAs layer are shown to play an important role in determining the photoresponse. We present photocurrent per incident photo data, as a function of incident light energy, at a variety of external biases. We also present current‐voltage curves taken while samples were illuminated by an incandescent lamp. Zero bias photocurrent consistent with electron transport from the nondegenerate region beneath the AlAs to the degenerate region forming the surface is observed. As negative voltage is applied to the top of the sample, this photocurrent changes sign. These results are explained by introducing the concept of a ‘‘collecting interface’’ to account for fields and scattering in the AlAs. Further, we explain why the shape of the photocurrent spectrum depends upon the sign of the photocurrent.