B. Koiller et al., OPTICAL EFFECTS OF INTERDIFFUSION IN GAAS ALAS HETEROSTRUCTURES - ATOMIC-SCALE CALCULATIONS/, Applied physics letters, 69(16), 1996, pp. 2423-2425
We investigate the effects of atomic interdiffusion in the optical pro
perties of AlAs/GaAs quantum wells through tight-binding model calcula
tions. Ensembles of supercells, each cell containing up to similar to
10(4) atoms with periodic boundary conditions, are used to simulate th
e heterostructures. The oscillator strength f of optical transitions a
t the absorption threshold is calculated as a function of the quantum-
wells width Wand the diffusion length L. As L increases, f undergoes a
discontinuous transition to zero, indicating indirect-gap behavior fo
r L larger than a critical value of the diffusion length. A unified be
havior of f as a function of L/W-1.7 is found. This permits relating o
ptical properties to structural properties through simple fitting form
ulas. (C) 1996 American Institute of Physics.