PHOTOVOLTAIC IV-VI ON SI INFRARED-SENSOR ARRAYS FOR THERMAL IMAGING

Photovoltaic narrow-gap IV-VI (lead chalcogenide) infrared sensor arra ys on Si substrates have the potential for low-cost infrared focal-pla ne arrays. The arrays can be bump bonded to readout multiplexers, or b e grown on prefabricated active Si substrates containing the whole rea dout circuits. Sensitivities are similar to that of Hg1-xCdxTe, but pr ocessing procedures are much less demanding. This is because the struc tural quality of even heavily lattice-mismatched IV-VI layers is adequ ate to fabricate devices with good sensitivities, because 2- to 4-mu m layer thickness suffices, and because good homogeneity in ternary Pb1 -xSnxSe for the 8- to 12-mu m range is much easier to obtain than in H g1-xCdxTe. New results are presented on the molecular beam epitaxial g rowth of the layers, including a very thin CaF2 buffer needed for comp atibility reasons, and a new photolithographic patterning technique su ited for full wafer processing has been developed to fabricate the sen sor arrays. First thermal images using these chips are demonstrated.