UNRESOLVED QUESTIONS IN WEAK-LOCALIZATION IN SEMICONDUCTORS

A review of weak localization theory is presented in application to el ectron transport in semiconductors. While the theory qualitatively wor ks well going into more microscopic level reveals difficulties. The im portant questions concern relaxing contact potential assumption by usi ng weekly screened potential, effect of impurity correlations, and tak ing into account spatial distribution of impurities and wave function modulation. The origin of weak-antilocalization in strictly two-dimens ional semiconductor systems is analyzed. There are two possible source s of this phenomenon: (1) crystalline: inversion asymmetry term and in terface or Rashba term, and (2) resulting from the presence of many su bbands. The first mechanism does not seem to agree with experimentally extracted dispersion relations for quasi two-dimensional systems. The second mechanism cannot explain a secondary maximum for magnetoresist ance observed in some systems. In addition to need to study interactio n effect, further progress can be achieved by using semiclassical theo ry with the correlated noise.