Slow relaxation of magnetoresistance in doped p -GaAs/AlGaAs layers with   partially filled upper Hubbard band
  We observed slow relaxation of magnetoresistance in quantum well structures GaAs-AlGaAs with a selective doping of both wells and barrier regions which allowed partial filling of the upper Hubbard band. Such a behavior is explained as related to magnetic-field driven redistribution of the carriers between sites with different occupation numbers due to spin correlation on the doubly occupied centers. This redistribution, in its turn, leads to slow multi-particle relaxations in the Coulomb glass formed by the charged centers. 
N.V.Agrinskaya, V.I.Kozub, D.V.Shamshur and A.Shumilin