ELECTRONIC AND OPTICAL-PROPERTIES OF LATERALLY COMPOSITION-MODULATED ALXIN1-XAS, GAXIN1-XP, AND GAXIN1-XAS ALLOYS

Results of a systematic study of the band structure and optical proper ties of laterally-composition-modulated semiconductor alloys AlxIn1-xA s, GaxIn1-xP, and GaxIn1-xAs are reported. [110] composition modulatio n occurs spontaneously during growth of (001) short-period superlattic es or bulk epilayers of these alloys. The effect of this long-range la teral modulation is modeled using k . p theory and the envelope-functi on approximation, while the vertical short-period superlattice is emul ated by a uniaxial perturbation. We have studied the dependence of the electronic and optical properties of such structures on the modulatio n amplitude, profile, and negative feedback due to the coherency strai n field. We find that (i) among the three-alloy systems, for a given m odulation amplitude, the largest band-gap reduction can be achieved in AlxIn1-xAs, and the smallest in GaxIn1-xAs, (ii) a step-function modu lation gives a larger band-gap reduction than a sinusoidal modulation; (iii) when the coherency strain is tetragonal in the modulated direct ion, a strong in-plane optical anisotropy is expected and when it is t etragonal in the growth direction, a weak in-plane optical anisotropy is anticipated; (iv) the vertical short-period superlattice enhances t he band-gap reduction, but reduces the in-plane optical anisotropy; an d (v) the lateral composition modulation is inherently associated with a diminishing of the vertical short-period superlattice. The possibil ity and conditions of type-II band alignment in these modulated struct ures are discussed. [S0163-1829(98)05519-2].