A dual band detector includes a substrate, a composite barrier, a first absorber on the substrate and on a light incident side of the composite barrier, the first absorber for detecting first infrared light wavelengths, a second absorber on the composite barrier on a side opposite the light incident side, the second absorber for detecting second infrared light wavelengths, wherein a bandgap of the first absorber is larger than that of the second absorber, wherein the composite barrier includes a first secondary barrier, a primary barrier, and a second secondary barrier, wherein the first and second secondary barriers may have a lower bandgap energy than the primary barrier, wherein the first or the second secondary barrier may have a doping level and type different from that of the primary barrier, and wherein at least the primary barrier blocks majority carriers and allows minority carrier flow.