Quantum interference and spin-orbit effects in the heterostructure with the 2D hole gas in the Si0.2Ge0.8 quantum well

The magnetic field (∼ 110 kOe) dependences of resistance of the Si0.7Ge0.3/Si0.2Ge0.8/Si0.7 Ge0.3 heterostructure with a 2D hole gas in the Si0.2Ge0.8 quantum well were measured at T = 0.335-10 K with varying current between 100 nA and 50 μA. It was found that in high magnetic fields there occurred Shubnikov - de-Haas oscillations, while in weak fields (H &le kOe) a positive magnetoresistance transforming than in a negative one was observed. This peculiarity is due to the effects of weak localization of 2D charge carriers with very close spin-orbit and inelastic scattering time, τso and τφ, respectively. This suggests that the spin states are splitted in response to the perturbing potential associated with the generation of a two-dimensional potential well (Rashba mechanism). The analysis of the effects of weak localization yields the characteristic relaxation times: τφ = 7.2T-1&middot10-12 s and τSO = 1.36&middot10-12 s. The latter characteristic provided of estimating the of spin splitting value for the heterostructure in question (Δ = 2.97 meV).