Optical Properties of a Quantum Well of A_1−x Bx Alloy Semiconductor in the Coherent Potential Approximation

Abstract

We have theoretically studied optical properties of a quantum well (QW) in which the well region is constructed from a binary alloy semiconductor A_1−xB_x in the coherent potential approximation (CPA). A tight binding model is used for a single particle (electron, hole, Frenkel exciton) in the well composed by a rectangular array of N_xx N_yx N_z sites. The effect of the diagonal randomness is reduced to the coherent potential σ( E), which is assumed to be the same for all sites, and is selfconsistently determined with the average Green’s function. For a slab (∞, ∞, N_z) and wire (∞, N_y, N_z), the density of states ( E) is composed of N_z (or N_yx N_z) subbands, each shows the two (one)-dimensional van-Hove singularity. When x (or 1−x) is small, a B (A) impurity-band always appears at the lower (higher) energy side of the lowest (highest) host-band. The change of ( E) and the absorption spectrum by changing the well-width and the dimensionality is discussed in detail.