GaAs/InGaAs quantum well infrared photodetector with a cutoff wavelength at 35 μm

GaAs/InGaAs far-infrared quantum well photodetectors based on a bound-to-continuum intersubband transition with a (zero response) cutoff wavelength of 35 mu m are reported. A peak responsivity of 0.45 A/W and detectivity of 6.0 x 10(9) cm root Hz/W at a wavelength of 31 mu m and a temperature of 4.2 K have been experimentally achieved. Infrared response was observed at temperatures up to 18 K, A calculated responsivity spectrum using a bound-to-continuum line shape corrected for phonon absorption is fitted to the experimental response. The calculated line shape without absorption gives a cutoff wavelength of 38 mu m with a peak responsivity of 0.50 A/W and a detectivity of 6.6 x 10(9) cm root Hz/W at 32 mu m. (C) 2000 American Institute of Physics. [S0003-6951(00)00931-1].