Monolithic infrared sensor array in heteroepitaxial Pb/sub 1-x/Sn/sub x/Se on Si with 12- mu m cutoff wavelength

An array of photovoltaic infrared sensors with cutoff wavelengths as high as 12 mu m has been fabricated in a narrow-gap semiconductor layer (Pb/sub 1-x/Sn/sub x/Se, LTS) grown heteroepitaxially on Si. The LTS sensors are diffusion noise current limited down to 95 K, followed by a depletion noise dominated region. Resistance-area products are up to 0.3 Omega -cm/sup 2/ at 77 K (cutoff 11.6 mu m), and quantum efficiencies are >0.25 without antireflection coating. This corresponds to a junction noise limited detectivity D*>2*10/sup 10/ cm Hz/W. The sensitivities achieved are only approximately=5 times lower than those of state-of-the-art photovoltaic Hg/sub 1-x/Cd/sub x/Te sensors with the same cutoff wavelength. Also presented are results which demonstrate that LTS growth and infrared (IR) sensor fabrication are compatible with active silicon substrates, thus allowing the construction of a heteroepitaxial but full monolithic narrow-gap semiconductor on a silicon IR focal plane array.