Localization and interaction effects in GaAs/AlGaAs heterostructures modified by 4He-ion implantation

Magnetoresistance is used to study localization and interaction in the 2-dimensional electron layer of 4He-ion implanted GaAs/Al-GaAs modulation doped heterostructures. At very low magnetic fields weak localization magnetoresistance can be fitted to theory, thereby determining the diffusion constant and the phase relaxation rate.

An unexpected saturation of the phase relaxation rate at low temperature was found to have an interesting relation to mobility and sample size. In the magnetic field range, where the cyclotron radius becomes of the order of the mean free path, the magnetoresistance was related to the effect of electron-electron interaction.

By comparison of the magnetoresistance at different implantation doses, we extracted a remnant quantum correction to the conductivity, which has not earlier been noticed. In samples with two Subbands populated interband scattering is observed to cause spin-orbit effects in the weak localization magnetoresistance.