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Shubnikov-de Haas oscillations and negative magnetoresistance under hot-electron conditions in Si/SiGe heterostructures

The energy loss rate of two-dimensional hot electrons has been studied in modulation-doped Si/SiGe heterostructures grown by ultrahigh-vacuum chemical vapour deposition using the damping of the amplitudes of Shubnikov-de Haas oscillations with applied electric field up to 2V cm-1. The samples investigated had a carrier concentration of 1*1012cm-2. The ohmic properties of the samples were studied by photo-Hall effect, conductivity and quantum Hall effect measurements. From comparison of the experimental data with calculations it is shown that the dominant energy loss mechanism is due to acoustic phonon emission via deformation potential coupling for electron temperatures between 1.8 and 7 K. In addition the electric field dependence of the negative magnetoresistance due to weak localization for electric fields up to 2.1 Vcm-1 was investigated for a lattice temperature of 1.8 K. The data were analysed to yield the dephasing time tau phi as well as the elastic scattering time tau e.