Molecular beam epitaxy growth of PbSe on BaF2-coated Si(111) and observation of the PbSe growth interface

Epitaxial growth of ${\mathrm{PbSe/BaF}}_{\mathrm{2}}{\mathrm{/CaF}}_{\mathrm{2}}$ heterostructures was carried out by molecular beam epitaxy (MBE) on Si(111) wafers. Successful transfer of 3-μm-thick PbSe epilayers was accomplished by bonding the MBE-grown samples face down to polished copper plates followed by the removal of the silicon substrate by dissolving the ${\mathrm{BaF}}_{\mathrm{2}}$ buffer layer in water. High-resolution x-ray diffraction measurements demonstrated that the PbSe epilayer maintained high-crystalline quality after transfer. In addition, optical Nomarski characterization of the exposed growth interface showed sets of parallel straight step lines consistent with glide of dislocations in the primary {100}〈110〉 glide system. Such features are evidence of the large thermal expansion mismatch strain that occurred in these layers.