We fabricated a communication wavelength photodetector based on intraband transition in GaN/AlN self-assembled quantum dot heterostructures. The quantum dot photodetector is based on in-plane transport and has a room temperature spectral peak responsivity of 8 mA/W at wavelength of 1.41 μm. We use multipass waveguide geometry to show that the polarization sensitive optical absorption spectrum of the heterostructure is nearly the same as its photocurrent spectral response. This establishes that the detector’s response is due to the presence of quantum dots in its active layer. We use photoluminescence, transmission, and intraband photocurrent spectroscopy to consistently describe the alignment between the energy levels of the quantum dots and that of the wetting layer.