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Dark current characteristics of 7 Monolayers (ML) InAs/ 4 ML GaSb SL pin photodiodes are simulated using ATLAS software. Using appropriate models and material parameters, we obtain good agreement between the simulated and the experimental dark current curves of photodiodes grown by molecular beam epitaxy. The n-type non-intentionally-doped (nid) SL samples exhibit a dependence of the lifetime with temperature following the T À1 2 law, signature of Shockley-Read-Hall (SRH) Generation-Recombination current. We also studied the dependence of the dark current with the absorber doping level. It appears that the absorber doping level must not exceed a value of 2 Â 10 15 cm À3 , above this value the dark current is increasing with increased doping level. However for this doping value, a dark current as low as 5 Â 10 À9 A/cm 2 , at 50 mV reverse bias at 77 K can be obtained. V

This work investigates midwave infrared Type-II InAs/GaSb superlattice (SL) grown by molecular beam epitaxy on GaSb substrate. In order to compensate the natural tensile strain of the InAs layers, two different shutter sequences have been explored during the growth. The first one consists of growing an intentional InSb layer at both interfaces (namely GaSb-on-InAs and InAs-on-GaSb interfaces) by migration enhanced epitaxy while the second uses the antimony-for-arsenic exchange to promote an 'InSb-like' interface at the GaSb-on-InAs interface. SLs obtained via both methods are compared in terms of structural, morphological and optical properties by means of high-resolution x-ray diffraction, atomic force microscopy and photoluminescence spectroscopy. By using the second method, we obtained a nearly straincompensated SL on GaSb with a full width at half maximum of 56 arcsec for the first-order SL satellite peak. Relatively smooth surface has been achieved with a root mean square value of about 0.19 nm on a 2 µm x 2 µm scan area. Finally, a p-i-n device structure having a cut-off wavelength of 5.15 µm at 77K has been demonstrated with a dark-current level of 8.3 x 10 -8 A/cm 2 at -50 mV and a residual carrier concentration of 9.7 x 10 14 cm -3 , comparable to the state-of-the-art. Highlights:-Two shutter sequences during the MBE growth of midwave InAs/GaSb SL have been investigated -The influence of the shutter sequence on the structural, morphological and optical properties has been studied -InAs/GaSb SL p-i-n photodiode with a dark-current level comparable to the state-of-the-art has been demonstrated

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