ANALYSES OF LOCALIZED CONFINEMENT POTENTIAL IN SEMICONDUCTOR STRAINEDWIRES AND DOTS BURIED IN LATTICE-MISMATCHED MATERIALS

Analytical and finite-element-method calculations have been conducted for obtaining strain distributions and consequent carrier confinement potential changes in semiconductor strained wires and dots made of lat tice-mismatched materials. The inhomogeneous strain distribution modif ies the confinement potentials locally, which causes carrier wave func tion localization. First, to obtain a fundamental strain distribution and band-structure change semiquantitatively, analytical calculations are performed in simple, symmetrical structures such as an InP cylinde r and an InP ball buried in GaAs or InGaP matrices assuming isotropic valence bands and isotropic elastic characteristics. Here, strain is f ound to exist in the surrounding matrices as well as in the wires and dots. This effect is peculiar to the strained wire and dot because in pseudomorphic strained layers there is no strain in surrounding matric es. Thus, the band structures are found to be greatly modified in the surrounding matrix as well as in the wire or dot. Hole effective masse s at the band edge are also calculated by diagonalizing a 4X4 orbital strain Hamiltonian. Furthermore, to calculate the effects in a realist ic structure, finite-element-method calculations are performed for a t riangle-shaped InP wire along the <110> direction, including anisotrop ic elastic characteristics. Calculated nonuniform strain within the wi re is found to modify the confinement potential, which localizes elect rons near the base. Valence subbands are largely split near the vertic es. From these results, the strained wires and dots are found to be ap plicable for quantum wires and dots, in which the quantum confinement effect will be enhanced by the modified confinement potential due to t he inhomogeneous strain. (C) 1994 American Institute of Physics.