19 March 1999 Mid-infrared silicon/germanium focal plane detector arrays
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Abstract
Highly p-doped silicon/silicon-germanium (Si/SiGe) quantum well (QW) structures have been grown by molecular beam epitaxy (MBE) on <100> Si substrates for mid-infrared (3(mu) - 5(mu) ; 8(mu) - 12(mu) ) detection. These detectors operate at 77 K and are based on hetero-internal photoemission (HIP) of holes from a highly p-doped SiGe quantum well into a undoped silicon layer. They are grown on weakly-doped (50(Omega) cm), double-sided polished Si substrate on which the highly p-doped Si1-xGex wells (p++ approximately 5 1020cm-3) are deposited. The Ge content, doping level and the well width determine the operating wavelength. The samples have been characterized by secondary ion mass spectroscopy (SIMS), X-ray diffraction, and absorption measurements. Single mesa detectors as well as large area focal plane arrays (FPA) with 256 X 256 pixels have been fabricated from these samples using standard Si integrated processing techniques. Dark- and photocurrents have been measured at 77 K and up to 225 K. Broad photoresponse curves with peak external quantum efficiencies up to 0.5% have been measured at 77 K and 4$u. Detectivities in excess of 2 1010 cm(root)Hz/W have been obtained. We demonstrate that by varying the well design of the SiGe HIP detectors by means of Ge-content, doping and Ge gradients in double and stacked multi-wells the photoresponse peak and the shape of the spectrum can be tuned over a wide wavelength range. The fabricated 256 X 256 Si/SiGe FPA array has a pixel size of 21 X 21(mu) 2 and a pitch of 24(mu) . The mesa detectors diameters range from 1 mm down to 125(mu) . The epitaxial versatility and the compatibility of the Si/SiGe array fabrication compared to the existing silicide fabrication process demonstrates the advantages of the SiGe system in comparison over commercially used silicide detectors.
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Hartmut Presting, Hartmut Presting, Johannes Konle, Johannes Konle, Markus Hepp, Markus Hepp, Horst Kibbel, Horst Kibbel, Klaus Thonke, Klaus Thonke, Rolf Sauer, Rolf Sauer, Wolfgang A. Cabanski, Wolfgang A. Cabanski, Milan Jaros, Milan Jaros, } "Mid-infrared silicon/germanium focal plane detector arrays", Proc. SPIE 3630, Silicon-based Optoelectronics, (19 March 1999); doi: 10.1117/12.342804; https://doi.org/10.1117/12.342804
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