Weak localization and intersubband transitions in delta-doped GaAs

The negative magnetoresistance in delta-doped GaAs is investigated experime ntally. It is shown for highly perfect structures that the value of the pre factor in the expression for the negative magnetoresistance significantly e xceeds the theoretical value for a two-dimensional film with a single fille d size-quantized subband. The role of a large number of filled subbands and intersubband transitions is discussed. It is shown that the symmetry of th e wave functions and the scattering potential in delta-doped layers can cau se the times of interband transitions between subbands with different parit y (tau(i,j)) to be greater than the phase-relaxation time of the wave funct ion (t(phi)). Such a relation between tau(i,j) and tau(phi) should be manif ested as a significant increase in the prefactor. (C) 1998 American Institu te of Physics. [S1063-7826(98)00912-0].