Interface states have been shown to have an appreciable effect on the performance of p-GaAs multilayer (p(+)-i-p(+)-i-...) homojunction interfacial work function internal photoemission (HIWIP) far-infrared detectors. In this article, a comparison of detector performance was made of p-GaAs HIWIP detectors with different interface state densities, with the emphasis on the detector's dark current, noise, and capacitance characteristics.