  Band Structures and optical matrix elements of quantum wires(QWR's) made of
short-period superlattices(SPS) with strain-induced lateral ordering(SILO) are
investigated theoretically via an effective bond-orbital model(EBOM) combined
with a valence-force field(VFF) model. Valence-band anistropy, band mixing, and
effects due to local strain distribution at the atomistic level are all taken
into account. In particular, Ga(1-x)In(x)As QWR's grown by SILO process are
considered. A VFF model is used to find the equilibrium atomic positions in the
SILO QWR structure by minimizing the lattice energy. The strain tensor at each
atomic(In or GA) site is then obtained and included in the calculations of
electronic states and optical peroperties. It is found that different local
arrangement of atoms leads to very different strain distribution, which in term
alters the optical properties. In particular, we found that the optical
anisotropy can be reversed due to the change in shear strain caused by the
inter-change of atomic positions. Good agreement with the existing experimental
data on band gap and optical anisotropy can be obtained when a 2D alloy
structure with lateral composition modulation in the InAs/GaAs interface planes
of the SPS is used. Our studies revealed the possibility of "shear-strain
engineering" in SILO QWR light-emitting devices to achieve desired optical
anisotropy.
