Epitaxy of narrow gap IV-VI materials on Si(111) and Si(100) substrates: growth, properties, and thermal mismatch strain accommodation

Abstract

IV-VI materials (PbTe, PbSe, Pb<SUB>1-x</SUB>Sn<SUB>x</SUB>Se) are grown by molecular beam epitaxy onto Si(111) and Si(100) substrates. Device quality layers are obtained on Si(111), if a very thin CaF<SUB>2</SUB>, or a stacked CaF<SUB>2</SUB>/BaF<SUB>2</SUB> buffer layer is employed. For these layers, thermal mismatch strain relaxation occurs by glide along the main {100} glide planes inclined by 54 degrees with respect to the surface. Cumulative plastic deformation on temperature cycling up to 500% was observed even at cryogenic temperatures, while the structural quality of the layers was only slightly adversely affected by such extreme plastic deformations. Interaction probabilities between moving dislocations were estimated to be below 10<SUP>-5</SUP>. Epitaxial growth of IV-VI materials directly on Si (without buffer layer) is possible, too. However, the structural quality is inferior. On Si(111), PbSe with either (100), (111) or mixed (111) and (100) orientation, depending on growth temperature, is obtained. Single oriented (100)PbSe layers result on Si(100). Strain relaxation occurs via the same mechanisms as for layers grown with buffer layers: On Si(111), strain relaxes by slip, while on Si(100), both relaxation by plastic deformation as well as by cracking is observed. The latter occurs for layers thicker than about 0.5 micrometers only.