GAAS ALGAAS QUANTUM-WELL PHOTODETECTORS WITH A CUTOFF WAVELENGTH AT 28 MU-M/

We demonstrate the longest (lambda(c)=28.6 mu m) far-infrared quantum well photodetectors (QWIPs) based on a bound-to-bound intersubband tra nsition in GaAs/AlGaAs. The responsivity is comparable with that of mi d-infrared GaAs/AlGaAs and InGaAs/GaAs QWIPs, A peak responsivity of 0 .265 A/W and detectivity of 2.5 x 10(9) cm root Hz/W at a wavelength o f 26.9 mu m and 4.2 K have been achieved, Based on the temperature dep endent dark current and responsivity results, it is expected that simi lar performance can be obtained at least up to 20 K. (C) 1998 American Institute of Physics.