Abstract
Photovoltaic narrow-gap IV-VI (lead chalcogenide) infrared sensor arrays on Si substrates have the potential for low-cost infrared focal-plane arrays. The arrays can be bump bonded to readout multiplexers, or be grown on prefabricated active Si substrates containing the whole readout circuits. Sensitivities are similar to that of Hg<sub>1-<i>x</i></sub>Cd<sub><i>x</i></sub>Te, but processing procedures are much less demanding. This is because the structural quality of even heavily lattice-mismatched IV-VI layers is adequate to fabricate devices with good sensitivities, because 2- to 4-μm layer thickness suffices, and because good homogeneity in ternary Pb<sub>1-<i>x</i></sub>Sn<sub><i>x</i></sub>Se for the 8- to 12-μm range is much easier to obtain than in Hg<sub>1-<i>x</i></sub>Cd<sub><i>x</i></sub>Te. New results are presented on the molecular beam epitaxal growth of the layers, including a very thin CaF<sub>2</sub> buffer needed for compatibility reasons, and a new photolithographic patterning technique suited for full wafer processing has been developed to fabricate the sensor arrays. First thermal images using these chips are demonstrated.
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