Magnetoresistance and electronic structure of asymmetric GaAs/AlGaAs double quantum wells in the in-plane/tilted magnetic field

Bilayer two-dimensional electron systems formed by a thin barrier in the GaAs buffer of a standard heterostructure were investigated by magnetotransport measurements. In magnetic fields oriented parallel to the electron layers, the magnetoresistance exhibits an oscillation associated with the depopulation of the higher occupied subband and the field-induced transition into a decoupled bilayer. Shubnikov-de Haas oscillations in slightly tilted magnetic fields allow to reconstruct the evolution of the electron concentration in the individual subbands as a function of the in-plane magnetic field. The characteristics of the system derived experimentally are in quantitative agreement with numerical self-consistent-field calculations of the electronic structure.Comment: 6 pages, 5 figure

Anisotropic Microwave Absorption in High-Tc\text{}_{c} like Semiconductor Superconducting Superlattices (001) PbTe-PbS

The anisotropic microwave absorption in the presence of alternative magnetic field has been studied for the first time in superconducting super-lattices based on PbTe-PbS, which are layered anisotropic systems similar to high T$\text{}_{c}$ superconductors. A new method of study has been used. The microwave response was detected under broad-band conditions and compared with the results of synchronous detection. All the features which have been observed in high T$\text{}_{c}$ materials are clearly seen here

SnTe Phase Transition in Strained Superlattices PbTe/SnTe

An anomaly of the in-plane conductivity is observed in the superlattices PbTe/SnTe on (001)KCl in the temperature region of 60-130 K. The anomaly is caused by a structural phase transition in SnTe layer and as a result, the transition induced formation of defects. These defects are additional scattering centres which decrease the superlattice conductivity

Piezoelectric Effect in Coherently Strained B-Doped (001)SiGe/Si Heterostructures

We report on two methods which illustrate piezoelectric effects in the strained Si (100)Si $\text{}_{1-x}$/Ge$\text{}_{x}$ system. The non-contact sound excitation technique has been used to reveal the conversion of a high-frequency electric field E into acoustic waves at 77 K which can also be modulated by a dc applied bias voltage (±30 V). The sample was an MBE grown modulation doped Si $\text{}_{0.88}$Ge$\text{}_{0.12}$/(001)Si structure with a carrier sheet density 2.0 × 10 $\text{}^{11}$ cm$\text{}^{-2}$ and a 4.2 K mobility 10500 cm$\text{}^{2}$ V$\text{}^{-1}$ s$\text{}^{-1}$. We deduce that the observed high-frequency electric field acoustic wave conversion is associated with a piezoelectric-like effect possibly due to ordering in the strained SiGe alloy or symmetry breaking effect near Si/SiGe interface. Further evidence is provided by the existence of a piezoelectric phonon interaction in the hot hole energy relaxation mechanism determined from high electric field Shubnikov de Haas He$\text{}^{3}$ low temperature measurements

The resonant tunneling of holes through double-barrier structures with InAs QDs at the center of a GaAs quantum well

The effect of InAs quantum dots (QDs) grown in the center of a GaAs quantum well on the tunneling characteristics of resonant-tunneling diodes based on p-AlAs/GaAs/AlAs heterostructures is studied. The introduction of QDs results in a shift and broadening of resonance peaks in the current-voltage characteristics of the diodes; however, this effect is found to be strongly dependent on the number of the 2D subband involved in the tunneling. The obtained dependence is attributed to origination of the fluctuation potential in the vicinity of the QD layer. © 2005 Pleiades Publishing, Inc