In this report, we are comparing two different QDIP architectures capped with quaternary and ternary layer of different barrier thicknesses and effect of rapid thermal annealing on the device performances. Low temperature power dependent PL spectra exhibit a multimodal distribution of the QDs in all the heterostructures which has been confirmed by XTEM. High thermal stability upto 800°C i.e. minimum PL peak shift in terms of wavelength was observed in all quaternary coupled devices with annealing compared to ternary (it was up to 700°C) capped QDIP. The vertical strain propagating from underlying QDs prevents the inter-diffusion by maintaining a strain relaxed state. Minimum Dark current density was observed in quaternary capped QDIP with total capping thickness of 15nm and one order enhancement in detectivity compared to ternary. Quaternary capped QDIP with 12 nm total capping thickness was most red shifted and a peak spectral response was observed at 7.3μm. Compared to ternary all quaternary devices showed narrow spectrum with less than 20% spectral line-width. Quaternary capped QDIP with 15 nm total capping thickness was annealed and devices were fabricated using 2 step lithography process. For 750°C annealed QDIP a maximum operating temperature of 140K with 5-fold increase in photocurrent compared to other was observed. © 2015 SPIE.