X-ray-diffraction study of size-dependent strain in quantum-wire structures

We report a synchrotron x-ray-diffraction study of the strain field in embedded ${\mathrm{In}}_{0.2}$${\mathrm{Ga}}_{0.8}$As/GaAs (001) quantum wires of widths 50–250 nm. Our results show a size-dependent orthorhombic lattice deformation in the wires and a linearly strained interfacial region near the wire sidewalls. The measured strain is responsible for an unusual band-gap energy increase that is several times larger than the quantum confinement effect, indicating that strain effects contribute significantly to band-edge energies in this and other quantum structures. © 1996 The American Physical Society.