DIMENSIONALITY EFFECTS ON STRAIN AND QUANTUM CONFINEMENT IN LATTICE-MISMATCHED INASXP1-X/PNP QUANTUM WIRES

The dependence of strain and quantum-confinement effects on the lateral size of lattice-mismatched InAs0.48P0.52/InP quantum wires has been investigated experimentally and theoretically. Photoluminescence experiments show that the blueshift of the transition energy corresponding to wire-width reduction is remarkably larger for lattice-mismatched wires than for lattice-matched wires. Magneto-optical measurements show that the lateral quantum-confinement effect is only partially responsible for the observed blueshift, and indicate that strain energy is wire-size dependent. Numerical calculations confirm that the strain configuration of quantum wires is very different from that of strained quantum films even when the wires are wide enough to exhibit only small quantum-confinement effects. Strain is nonuniform and strongly dependent on wire size, while the composition of the well region is constant. The energy levels of quantum wires are deduced by diagonalizing the Hamiltonian matrix using the calculated strain values. The calculated change in the hydrostatic and shear components of strain energy, together with the quantum-confinement effect, explains the observed blueshift. This show that the uniform biaxial strain model cannot be applied to quantum wires, and a proper calculation of strain distribution is unavoidable to estimate the band structure of strained quantum wires.