Saturation of electron phase breaking time in GaAs/AlGaAs quantum wires

We have systematically studied an electron phase breaking time in AlGaAs/GaAs quantum wires by measuring the weak-localization effect. The phase breaking time does not saturate down to 0.5 K for quantum wires whose undoped AlGaAs spacers are not thinner than 30 nm, while it saturates below 1 K for quantum wires whose spacers are not thicker than 15 nm. The saturated magnetoconductance shows no antilocalization features characteristic of a spin–orbit interaction. A spin–flip scattering by paramagnetic electron-trapped donors is discussed as one of the possible origins of the saturation.