Abstract
MBE growth and infrared device fabrication with epitaxial IV-VI layers on Si substrates are reviewed. Epitaxy on Si substrates is achieved using a stacked BaF<sub>2</sub>/CaF<sub>2</sub> or CaF<sub>2</sub> buffer layer. With buffers containing no BaF<sub>2</sub>, standard photolithographic delineation with wet-etching techniques can be used. Photovoltaic IV-VI sensors with cutoff wavelengths ranging from 3 to 14 μm are fabricated in PbS, PbSe<sub>1-<i>x</sub></i>S<sub><i>x</i></sub>, PbEu<sub>1-<i>x</sub></i>Se<sub><i>x</sub></i>, PbTe, or Pb<sub>1-<i>x</sub></i>Sn<sub><i>x</sub></i>Se layers on Si (111) substrates. They offer the possibility for low-cost infrared focal plane arrays with sensitivities similar to Hg<sub>1-<i>x</sub></i>Cd<sub><i>x</sub></i>Te, but with much less demanding material processing steps. A 13-mm-long linear array with 10.5-μm cutoff wavelength has inhomogeneities in cutoff below 0.1 μm. Some arrays were grown on prefabricated active Si substrates containing the whole readout circuits. First thermal images using these chips are demonstrated. The induced mechanical strain resulting from the different thermal expansion of IV-VIs and Si relaxes down to cryogenic temperatures even after many temperature cycles because of dislocation glide in the main {100} glide planes.
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