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Quantum point contacts fabricated using a backgated two-dimensional electron-gas system show clear quantized features and a 0.7 anomaly in conductance. Using these density-tunable point contacts, we have studied the behavior of the 0.7 anomaly. The 0.7 step shifts down to around 0.5 as the electron density is decreased under a zero magnetic field. This suggests that electron-electron interactions play an important role in forming the conductance anomalies of quantum point contacts.

We report experimental studies of temperature-dependent Auger recombination coefficients in self-assembled quantum dots. The results are based on a study of temperature-dependent large signal modulation experiments made on self-organized In0.4Ga0.6As/GaAs quantum dot lasers. The Auger coefficient decreases from ∼8×10−29 cm6/s at 100 K to ∼4×10−29 cm6/s at 300 K. This behavior, which is different from results in other higher-dimensional systems, is explained in terms of the temperature dependence of electron-hole scattering in the dots and contribution from higher lying states in the dot and adjoining layers.

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