Localization and electron-electron interaction effects in magnetoresistance of p-type Ge/Ge_(1-x)Si_x heterostructures

We report on the results of investigation the conductivity and magnetoresistance (MR) temperature dependencies for the two strained multilayer p-type Ge/Ge_{1-x}Si_x heterostructures. The usual logarithmic temperature dependencies for zero magnetic field conductivity due to the weak localization (WL) and electron- electron interaction (EEI) effects take place in both samples. For one of the samples the negative MR is observed in a whole range of magnetic fields up to ~1T at T <=12K, but for the other sample the MR transforms from the negative to positive at B >= 0.2T and T >=1.3K. We attribute such a behavior to the interplay of two types of holes due to partial filling of the second subband. Extrapolation of the observed high-field parabolic MR to B = 0 allows to separate WL and EEI contributions to the total quantum corrections to conductivity at B = 0 resulting for both of our structures in that EEI part is ~2/3 and the WL part is ~1/3.