Dual-band unipolar barrier infrared photodetector based on InGaAsSb bulk and type-II InAs/GaSb superlattice absorbers

Highlights: • An InGaAsSb/AlGaSb/T2SL nBn detector structure was epitaxially grown and characterized. • A high crystal quality of InGaAsSb and T2SL absorbers with different bandgaps was achieved. • A dual-band SWIR/MWIR detection was enabled by switching the applied bias polarity. • High detectivities were obtained in both SWIR and MWIR spectral ranges at 77 K. -- Abstract: We reported on the material and device characterization of a dual-band unipolar barrier infrared photodetector with n-In_0.28Ga_0.72As_0.25Sb_0.75 bulk and InAs/GaSb type-II superlattice (T2SL) absorbers. X-ray diffraction (XRD) analysis revealed that a high crystallinity of the InGaAsSb and T2SL absorbers was obtained, evidenced by the narrow XRD full-width-at-half maximums of ~86 and ~53 arcsec, respectively. The detector dark current for the T2SL absorber operated in the mid-wavelength infrared band was diffusion limited at T > 260 K while the generation-recombination (G-R) current became dominant at T = 180–240 K. In case of the InGaAsSb absorber operated in the short-wavelength infrared band, the dominant dark current was the G-R current through midgap centers at T > 240 K whereas the G-R current caused by dopant-related deep levels could be dominated at T = 200–240 K. A bias selectable dual-band operation in short-/mid-wavelength infrared (SWIR/MWIR) ranges was demonstrated by the InGaAsSb and T2SL absorbers with 90% cutoff wavelengths of ~2.2 µm and ~5.3 µm, respectively. At T = 77 K, the barrier detector exhibited high specific detectivities of 2.2 × 10¹⁰ cm Hz^1/2/W and 2.6 × 10¹¹ cm Hz^1/2/W at + 60 mV and −200 mV in the SWIR and MWIR ranges, respectively.