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 μm are reported. A peak responsivity of 0.45 A/W and detectivity of ${\text{6.0×10}}^9 \mathrm{cm}\sqrt{\mathrm{Hz}}\mathrm{/W}$ at a wavelength of 31 μm 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 μm with a peak responsivity of 0.50 A/W and a detectivity of ${\text{6.6×10}}^9 \mathrm{cm}\sqrt{\mathrm{Hz}}\mathrm{/W}$ at 32 μm.