Electroreflectance spectroscopy of Si-GexSi1−xquantum-well structures

Abstract

Electroreflectance spectroscopy of ${\mathrm{Ge}}_{\mathrm{x}}$ ${\mathrm{Si}}_{1\mathrm{-}\mathrm{x}}$ decoupled multiple-quantum-well structures grown by molecular-beam epitaxy has been used to yield confinement energy and strain shifts for the $E_0$ and $E_1$ optical transitions. The strain induced by lattice mismatch decouples the valence band at the zone center permitting resolution of the strain-split $E_0$ valence-band states. Confinement of electrons and holes in quantum-well states has an additional important effect on the optical transition energies for narrow (<50 Å) wells. Good quantitative agreement is obtained between experimental results and the full theoretical treatment of strain and confinement.