Quantum confinement of phonon modes in GaAs quantum dots

Phonon modes in spherical GaAs quantum dots (QDs) with up to 11,855 atoms ( 8 nm in size) are calculated by using an empirical microscopic model. The g roup theory is employed to reduce the computational intensity, which furthe r allows us to investigate the quantum confinement of phonon modes with dif ferent symmetries and reveals a phenomenon that phonon modes with different symmetries have different quantum confinement effect. For zinc-blende stru cture, the modes with the A(1) symmetry has the strongest quantum confineme nt effect and the T-1 modes the weakest. This could cause a crossover of sy mmetries of the highest frequency from A(1) to T-2 when the size of QDs dec reases. (C) 1999 Elsevier Science Ltd, All rights reserved.