PHOTOVOLTAIC LEAD-CHALCOGENIDE IR-SENSOR ARRAYS ON SI FOR THERMAL IMAGING APPLICATIONS

Linear arrays of photovoltaic infrared sensors for thermal imaging applications are fabricated in narrow gap semiconductor layers grown heteroepitaxially on Si. Epitaxy is achieved using stacked intermediate BaF2SrF2CaF2 buffers to overcome the large lattice-as well as thermal expansion mismatch. The arrays consist of 66 elements and cover cut-off wavelengths ranging from 3 to above 12 μm. Extrapolated resistance-area products of the best PbTe sensors (cut-off wavelengths5.7 μm) on Si are up to 20 000 Ω cm2 at 77 K. They approach those of similar HgCdTe sensors fabricated in bulk or epitaxial material on CdTe substrates. Mean detectivities of whole PbTe on Si arrays at 90 K are as high as DJNL* = 1.5×1012 cm√Hz/W. © 1990.