A research team from Georgia State University in Atlanta, the National Research Council's Institute for Microstructural Sciences in Ottawa and Cornell University in Ithaca, N.Y., has produced a GaAs/InGaAs quantum-well infrared photodetector that may challenge the dominance of germanium sensors in the far-IR. Far-IR detectors have applications in astronomy and satellite mapping. The team, which reported its work in the July 31 issue of Applied Physics Letters, produced the new photo-detector by molecular beam epitaxy and wet chemical etching of the GaAs barriers and InGaAs wells. The sensor displayed a cutoff at 35 µm and a peak responsivity of 0.45 A/W at 31 µm under experimental conditions at 4.2 K.