Quantum-confined biexcitons i grown on Si(001)

We report experimental evidence for the existence of three-dimensionally (3D) -confined biexcitons in a strain-relaxed (Formula presented)(Formula presented) layer grown on a stepwise graded buffer on Si(001) by ultrahigh vacuum chemical vapor deposition. A calculation of the photoluminescence line shape based on a simple model is found to be in good agreement with experiment. From this theoretical fit we deduce a binding energy of 1.55 meV for the 3D-confined biexcitons. This binding energy is larger than the reported value of 1.36 meV for a free biexciton in Si, indicating a quantum-confinement effect. © 1997 The American Physical Society.