Electron spin beats in InGaAs/GaAs quantum dots

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Abstract
Time-resolved picosecond spectroscopy is used for the first time to study optical orientation and spin dynamics of carriers in self-organized In(Ga)As/GaAs quantum-dot (QD) arrays. Optical orientation of carriers created by 1.2 ps light pulses, both in the GaAs matrix and wetting layer, and captured by QDs is found to last a few hundreds of picosecond. The saturation of electron ground state at high-excitation-light intensity leads to electron polarization in excited states close to 100% and to its vanishing in ground state. Electron-spin quantum beats in a transverse magnetic field are observed for the first time in semiconductor QDs. We thus determine the quasi-zero-dimensional electron g factor in In0.5Ga0.5As/GaAs QDs to be: |g ⊥|=0.27±0.03.