The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. Abstract The Photon-Trap Structures for Quantum Advanced Detectors (PT-SQUAD) program requires MWIR detectors at 200 K. One of the ambitious requirements is to obtain high (> 80 %) quantum efficiency over the visible to MWIR spectral range while maintaining high D* (> 1.0 x 10 11 cm √Hz/W) in the MWIR. A prime method to accomplish the goals is by reducing dark diffusion current

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... in the detector via reducing the volume fill ratio (VFR) of the detector while optimizing absorption. Electromagnetic simulations show that an innovative architecture using pyramids as photon trapping structures provide a photon trapping mechanism by refractive-index-matching at the tapered air/semiconductor interface, thus minimizing the reflection and maximizing absorption to > 90 % over the entire visible to MWIR spectral range. InAsSb with bandgap appropriate to obtaining a cutoff wavelength ~ 4.3 μm is chosen as the absorber layer. An added benefit of reducing VFR using pyramids is that no AR-coating is required. Compound-barrier (CB) detector test structures with alloy composition of the InAsSb absorber layer adjusted to achieve 200 K cutoff wavelength of 4.3 µm (InAsSb lattice-matched to GaSb). Dark current density at 200 K is in the low 10 -4 A/cm 2 at V d = -1.0 V. External QE ~ 0.65 has been measured for detectors with a Si carrier wafer attached. Since illumination is through the Si carrier wafer that has a reflectance of ~ 30 %, this results in an internal QE > 0.9. Downloaded From: http://proceedings.spiedigitallibrary.org/ on 03/29/2013 Terms of Use: http://spiedl.org/terms Proc. of SPIE Vol. 8012 80122S-3 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 03/29/2013 Terms of Use: http://spiedl.org/terms Proc. of SPIE Vol. 8012 80122S-5 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 03/29/2013 Terms of Use: http://spiedl.org/terms Proc. of SPIE Vol. 8012 80122S-6 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 03/29/2013 Terms of Use: http://spiedl.org/terms