Stability of the DX- center in GaAs quantum dots -: art. no. 185501

Using a first-principles band structure method, we study how the size of quantum dots affects the stability and transition energy levels of defects in GaAs. We show that, although a negatively charged DX- center is unstable in bulk GaAsSi with respect to the tetrahedral coordinated Si-Ga(-), it becomes stable when the dot size is small enough. The critical size of the dot is about 14.5 nm in diameter. The reason for the stabilization is the strong quantum-confinement effect, which increases the formation energy of Si-Ga(-) more than that of the DX- defect center. Our studies show that defect properties in quantum dots could be significantly different from those in bulk semiconductors.