Mid-wavelength infrared nBn photodetectors based on InAs/InAsSb type-Ⅱ superlattice with an AlAsSb/InAsSb superlattice barrier
InAs/InAsSb type-Ⅱ superlattice(T2SL)materials hold great promise for the development of mid-wave-length infrared photodetectors operating at high temperatures,as they avoid the defects caused by Ga atoms in InAs/GaSb T2SL and exhibit long minority carrier lifetime.To reduce the dark current,minority carrier unipolar barrier struc-tures,such as nBn detectors,are commonly employed.In mid-wavelength infrared InAs/InAsSb T2SL nBn photodetec-tors,the multielement alloy such as AlAsSb is typically utilized as the barrier layer to block the transport of majority car-riers.However,the small valence band offset(VBO)between the barrier and absorption layers leads to the saturation of photocurrent at high bias voltage,resulting in increased dark current.In this work,an AlAsSb/InAsSb T2SL barrier was designed to eliminate the VBO and reduce the bias dependency of quantum efficiency.The results show that the fab-ricated nBn photodetector exhibits a 50%cutoff wavelength of 4.5 μm at 150 K.The optical response of the photodetec-tor saturates under a small bias of-50 mV,achieving a peak responsivity of 1.82 A/W at 3.82 μm and a quantum effi-ciency of 58.8%.At 150 K and-50 mV applied bias,the photodetector exhibits a dark current density of 2.01×10-5 A/cm2 and a specific detectivity of 6.47×1011 cm·Hz1/2/W.
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