We present new results on structural and electronic properties of epitaxial lead chalcogenides on Si-substrates. A stacked MBE-grown CaF2/BaF2 buffer of 200 nm thickness serves to overcome the large lattice- and thermal expansion mismatches. Lead chalcogenide layers are grown by MBE or HWE with thicknesses of a few μm.
The X-ray rocking curve widths of these layers are below 200 arc sec. They are as low as curve widths of similar layers grown on bulk BaF2, or GaAs layers of comparable thicknesses on Si. The mechanical strain-state of the layers was determined with x-ray measurements and RBS channelling angular scans. Strain is below 4.10−4 at room temperature, indicating a near complete relaxation of the thermal and lattice misfit induced strains.
The quality of the layers is sufficient to integrate whole photovoltaic IR-sensor arrays.
We have fabricated linear arrays with cut-off wavelengths of 12 μm by using Pb1−xSnxSe, 5 μm with PbTe, and 3 - 4 gm with PbS and Pb1−xEuxSe. The structures withstand repeated cooling to the 80K operation temperature.