A dual-band homojunction interfacial workfunction internal photoemission infrared detector that responds in both near- and far-infrared (NIR and FIR) regions is reported. In the p+-i-p+ detector structure, the emitter is carbon doped to 1.5×1019 cm-3, and a 1 μm thick GaAs layer acts as the barrier, followed by another highly p-doped GaAs contact layer. The NIR response is due to the interband transition in GaAs barrier layer and the threshold wavelength observed at 0.82 μm is in good agreement with the 1.51 eV band gap of GaAs at 4.2 K. The intraband transition giving rise to FIR response is observed up to 70 μm. Interband responsivity was (under 100 mV reverse bias at 20 K) ∼8 A/W at 0.8 μm, while the intraband responsivity was ∼7 A/W. The detector has peak detectivities D*∼6×109 and 5×109 cm Hz1/2/W at 0.8 and 57 μm wavelengths, respectively, under 100 mV reverse bias at 20 K.