Quantum interference effects in p-Si1−xGex quantum wells

Quantum interference effects, such as weak localization and electronelectron interaction (EEI), have been investigated in magnetic fields up to 11 T for hole gases in a set of Si1−xGex quantum wells with 0.13 < x < 0.95. The temperature dependence of the hole phase relaxation time has been extracted from the magneto-resistance between 35 mK and 10 K. The spin-orbit effects that can be described within the Rashba model were observed in low magnetic fields. A quadratic negative magneto-resistance was observed in strong magnetic fields, due to the EEI effect. The hole-phonon scattering time was determined from hole overheating in a strong magnetic field

Positive quasiclassical magnetoresistance and quantum effects in germanium quantum wells

Changes in the conductivity of p-type quantum-well heterostructures of Si(0.05)Ge(0.95) alloy are studied at temperatures ranging from 0.352-7.1 K and magnetic fields of up to 11 T. The distinctive feature of the sample was asymmetric doping, with layers of Si(0.4)Ge(0.6) with boron impurity concentrations of 2 . 10(18) and 8 . 10(18) cm(-3) positioned on opposite sides of the quantum well. Shubnikov-de Haas oscillations were observed clearly against the background of a high quasi-classical positive magnetoresistance. The field dependence of the magnetoresistance is well described by a function of the form rho(xx)(B)/rho(xx)(0)proportional to B(12/7), as predicted by a theory including the combined effect of both short-and long-range disorder. The contribution to the temperature and magnetic field dependences of the resistance owing to quantum corrections associated with weak localization and charge carrier interactions is determined. Strong spin-orbital scattering of holes on the quantum well is revealed by analyzing these corrections. A study of the variations in the amplitude of the Shubnikov-de Haas oscillations with temperature and magnetic field (including the monotonic behavior of the resistance with changing magnetic field) makes it possible to determine the effective mass of the charge carriers, m*=0.17m(0) The temperature dependence of the hole-phonon relaxation time was found by studying the overheating of charge carriers by an electric field. (C) 2010 American Institute of Physics. [doi:10.1063/1.3536348

Study of overheating effects in SiGe-based p-type heterostructures : methods of the hole temperature determination

The effect of charge carrier overheating is studied in the p-type Si/Si(0.87)Ge(0.13)/Si heterostructure. The hole temperature T(h) can be calculated using three different methods: From a comparison of the changes in the amplitude of the Shubnikov-de Haas oscillations under the influences of temperature and current, from a comparison of the change of phase relaxation time in the weak localization effect obtained at different temperatures and minimum current and at a given temperature but at different values of current, and from a comparison of the temperature and current dependence of the sample resistance. The temperature dependences values of T(h) obtained using three different methods were identical and exhibit transition of the two-dimensional system under study from the regime of "partial inelasticity" to that of small angle scattering at temperature lowering

Overheating effect and hole-phonon interaction in SiGe heterostructures

The effect of charge-carrier overheating in a two-dimensional (2D) hole gas is realized in a Si1-xGex quantum well, where x=0.13, 0.36, 0.8, or 0.95. The Shubnikov-de Haas (SdH) oscillation amplitude is used as a "thermometer" to measure the temperature of overheated holes. The temperature dependence of the hole-phonon relaxation time is found from an analysis of the change of the dependence of the amplitude of the SdH oscillations on temperature and applied electrical field. Analysis of the temperature dependence of the hole-phonon relaxation time reveals a transition of the 2D system from the regime of "partial inelasticity" to conditions of small-angle scattering