We demonstrate enhanced terahertz detection using photoconductive antennas based on self-assembled ErAs:GaAs nanoisland superlattices. Three detectors are compared; one each fabricated on low-temperature grown GaAs, radiation-damaged silicon-on-sapphire, and an ErAs:GaAs superlattice. The ErAs:GaAs based detector shows a strong enhancement in terahertz detection efficiency with respect to incident optical power, though optical saturation occurs more rapidly. Detected terahertz bandwidth and signal-to-noise ratios are simultaneously maintained or improved.