Long wavelength broadband normal incidence AlAs/AlGaAs X-valley quantum well infrared photodetector

The Letter demonstrates a long-wavelength broadband normal incidence infrared photodetector based on bound state to extended state interconduction sub-band transitions in AlAs/AlGaAs X-valley quantum wells. High infrared absorption coefficient and quantum efficiency ( alpha =1900 cm^-1, eta =19%), wideband long wavelength photoresponsivity ( lambda =7.8-17.1 mu m) and low dark current (I_D=10^-6 A at 68 K and V_b=1 V) are achieved.