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 group theory is employed to reduce the computational intensity, which further allows us to investigate the quantum confinement of phonon modes with different symmetries and reveals a phenomenon that phonon modes with different symmetries have different quantum confinement effect. For zinc-blende structure, the modes with the A1 symmetry has the strongest quantum confinement effect and the T1 modes the weakest. This could cause a crossover of symmetries of the highest frequency from A1 to T2 when the size of QDs decreases.