InP ring-shaped quantum-dot molecules grown by droplet molecular beam epitaxy

In this paper, the reflection high energy electron diffraction of the transition from a two-dimensional growth mode to a three-dimensional growth mode of InP ring-shaped quantum-dot molecule (QDM) formation in the matrices of In0.5Ga0.5P on semi-insulating GaAs(0 0 1) substrates was reported. All samples were grown by solid-source molecular beam epitaxy using the droplet epitaxy technique under different crystallization temperature conditions. The surface morphologies of InP ring-shaped QDMs were examined by atomic force microscopy and the photoluminescence (PL) spectra were obtained by the 478 nm line of an Ar+ laser with an InGaAs detector. The dependence of the PL ground-state peak energies as the function of power and temperature with the tendencies of PL peak and full width at half maximum were investigated and discussed.