Properties of expitaxial Pb1−xSnxSe on CaF2 covered Si(111) substrates

Epitaxial narrow gap Pb1−xSnxSe layers on Si-substrates are used for infrared focal plane arrays for thermal imaging in the 8–12 μm wavelength range. The density of threading dislocations in the 3–4 μm thick layers due to the lattice mismatch is about 3 × 107 cm−2, in accordance with the width of X-ray rocking curves (100 arc s range). These narrowest widths are obtained only in layers which exhibit high carrier mobilities. Due to the thermal expansion mismatch, misfit dislocations formed during growth glide on each temperature change along the {100} main glide planes. The interaction probabilities of such crossing dislocations leading to strain hardening is extremely low, a rough estimate leads to a value of 10−5. This is because the cumulative plastic deformation (applied by repeated temperature cycling) is as high as 500%.