Fig. 1. (Color online) (a) The schematic of the InAs/GaSb T2SL MWIR epi. structure with nBn structure. (b) TEM image of the absorber layer with InAs/GaSb 10/10 MLs. The inset on right corner shows a magnitude view taken in HAADF mode. (c) The schematics of the InAs/GaSb T2SL nBn device fabrication process. Fist, each pixel is isolated by etching the top contact layer and the barrier using C₆H₈O₇/H₃PO₄/H₂O₂/H₂O solution. After wet-treatment to remove a native oxide at the surface, SiO₂ passivation layer is deposited using PECVD. Finally, the contact metal is evaporated for both pixels and common electrode.

Fig. 2. (Color online) (a) The dark current density versus applied bias at 80 K. The identical fabrication process is used for device fabrication on the wafers A and B. Approximately, one order of magnitude higher dark current density is observed from the devices on the wafer A. (b) Arrhenius plots of the devices fabricated on the wafers A and B. Both devices demonstrate diffusion-limited current but different activation energies. The plot indicates that the minority carrier lifetime in the absorber layer of the devices on the wafer B is longer than those on the wafer A.

Fig. 3. (Color online) Spectral response of the devices fabricated on the wafers A and B. The cut-off wavelength of the devices on the wafer B is shorter than those on the wafer A. The result is consistent with the results in Fig. 2, exhibiting difference activation energies.

Fig. 4. High-resolution X-ray omega-2theta scan data of InAs/GaSb T2SL and Al_0.2Ga_0.8Sb around GaSb (004) peak.

Table 1. Analysis of HRXRD patterns.