We use droplet epitaxy to create tensile-strained GaP quantum dots in a GaAs matrix. A strong biaxial tensile strain leads to the formation of a type-II band lineup with a transition energy lower than the bulk GaAs band gap. The luminescence transients exhibit highly non-exponential decay behavior with an average time constant of 11 ± 2 μs, which is more than three orders of magnitude longer than the lifetime of standard type-I quantum dots. The prolonged luminescence decay time for the GaP/GaAs dots confirms the formation of the type-II band alignment associated with the tensile strain.
The GaAs nanowires are grown on Si (111) substrates by Ga-assisted molecular beam epitaxy growth technique. The effect of SiO2 thickness on the structural properties of GaAs nanowires is investigated by Scanning Electron Microscope (SEM). The nucleation of GaAs nanowires related to the presence of a SiO2 layer previously coated on Si substrate. The results show that the density, length, and diameter of GaAs nanowires strongly depend on the oxidation time (or SiO2 thickness).
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