Fig. 2. (a)Bandgap diagram of nBn barrier detector,(b)spatial makeups of the various current components and barrier blocking in nBn detector,(c)bandgap diagram of the p-n photodiode,(d)the schematic Arrhenius plot of the dark current in a p-n photodiode and nBn device and comparision with Rule 07 & Law 19
Fig. 4. (a)Arrhenius plot of dark current at different reverse bias values for a 300×300 μm nBn detector,(b)photoresponse spectra at 150 K(the calculated spectral response(solid line)and the measured spectral response at a reverse bias of -0.6 V(dotted line)),(c)image captured by a 320×256 nBn FPA detector(BF ROIC)operating at 150 K and f/3,(d)the device structure of InAsSb/AlAsSb nBn MWIR detector,(e)the stimulated energy band diagram under reverse bias conditions of InAsSb/AlAsSb nBn MWIR detector,(f)the dark current density vs bias voltage as a function of the temperature of the InAsSb/AlAsSb nBn MWIR detector[54,58,60]
Fig. 5. Design of the InSb nBn barrier detector,(a)design of InSb nBn structure with InAlSb barrier layer including Al grading from 15% to 35%,(b)calculated energy band diagram at T = 110 K and V = 0 V of InSb/InAlSb/InSb nBn structure with 50 nm-thick InAlSb graded composition barrier layer,(c)Arrhenius plot of the dark current density collected at -50 mV where thermionic emission regime is identified,(d)J-V curves performed at 77 K of InSb-based nBn detector(solid line)and InSb PIN diode(dashed line),(e)J-V characteristics of nBn structure for different operating temperatures,from 105 K to 175 K,(f)Arrhenius behavior of three different types of InSb-based photodetectors[64,65,67]
Fig. 6. (a)Alignment between mini-bands in the active and barrier layers of a T2SLs XBp device,superimposed on the band gaps of InAs,GaSb,and AlSb,(b)the schematic diagram of the SWIR nBn photodetector with the inset showing the superlattice band alignment of the H-structure electron barrier[71,72]
Fig. 7. Design of the HgCdTe nBn barrier detector,(a)the schematic illustration of the structure of the HgCdTe nBn photodetector device,(b)cross-sectional device diagram and structural parameters,(c)measured dark and unfiltered blackbody illuminated I-V characteristics of planar MWIR HgCdTe nBn device at 77 K[30,79]
Fig. 8. Design of the two-dimensional materials nBn barrier detector,(a)the schematic diagram of the WS2 nBn vdW unipolar barrier photodetector,(b)simulated band diagrams of the device under different source-drain bias(Vds)conditions(WS2,h-BN,and PdSe2 flakes act as the absorber,barrier,and contact layer,respectively),(c)output characteristic curves of the nBn vdW unipolar barrier device under 520 nm laser illumination with increasing powers[94]