GaAs/InGaAs far-infrared quantum well photodetectors based on a bound-to-co
ntinuum (bc) and bound-to-quasibound (bq) intersubband transition with a cu
toff wavelength (zero response) up to 35 mum are reported. A peak responsiv
ity of 0.45 and 0.30 A/W and detectivity of 6 x 10(9) and 1.0 x 10(10) cm r
oot Hz/W at a wavelength of 31 mum and a temperature of 4.2 K respectively
for a be and a bq detector have been achieved. (C) 2001 Elsevier Science B.
V. All rights reserved.