GaAs/AlGaAs quantum well photodetectors with a cutoff wavelength at 28 μm

We demonstrate the longest (lambda(c)=28.6 mu m) far-infrared quantum well photodetectors (QWIPs) based on a bound-to-bound intersubband transition in GaAs/AlGaAs. The responsivity is comparable with that of mid-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 of 26.9 mu m and 4.2 K have been achieved, Based on the temperature dependent dark current and responsivity results, it is expected that similar performance can be obtained at least up to 20 K. (C) 1998 American Institute of Physics.