Single-electron spin-dependent transport in split-gate structures containing self-assembled quantum dots

Study of split-gate structures, in which self-assembled InAs quantum dots (QDs) are located near the region of 2D electron gas, has revealed Coulomb oscillations in the dependence of the tunnel current through a limited number of InAs QDs in a channel on the gate voltage, which correspond to the excited states of QDs with opposite spins. The Coulomb oscillations of the current were observed up to a temperature of ～20 K. The Coulomb energy ΔE _C was found to be 12.5 meV, a value corresponding to the theoretical estimates for p states of QDs in our experimental structures.     

Hydrostatic pressure investigations of resonant tunnelling through X-minimum-related states in a single barrier GaAs/AlAs/GaAs heterostructure

Abstract

We have investigated the resonant tunnelling of electrons through X-valley related states in a single AlAs barrier with Si donor & doping. Under high hydrostatic pressure all the peaks observed in the differential conductance-voltage (σ-V) characteristics shift with a pressure rate of -lSmeV/kbar, which is expected for X-minima related electronic states.     

Quasielastic scattering of light by a photoexcited electron-hole plasma induced in a GaAs layer in the presence of InAs quantum dots

The development of a method for registering quasielastic electronic light scattering spectra in the near-IR region, which makes it possible to detect light scattering by a photoexcited electron-hole plasma induced in a GaAs layer in the presence of a self-organized ensemble of InAs quantum dots, is reported. A substantial resonance intensification of such scattering, two orders of magnitude greater than the values established for the bulk material, is observed, and the main mechanism of such scattering is determined.     

Sulphur diffusion in GaAs-AlAs superlattices

Diffusion and heat treatment experiments in closed ampoules were carried out on two different molecular beam epitaxy-grown GaAs-AlAs superlattice wafers. All of the diffusion experiments were undertaken at 1000° C. The effects of varying the As and S vapour pressures as well as the diffusion time were investigated. Angle-lapping, transmission electron microscopy, X-ray photoelectron spectroscopy and secondary-ion mass spectroscopy were the techniques employed to analyse the samples. It was demonstrated that the diffusion of S enhances the group III interdiffusion or intermixing compared with the effect of plain heat treatment. It was also shown that S-induced intermixing has two origins, one being the diffusion of S and its effects on the concentration of native defects and the other being a mechanism related to the formation of a coating on the semiconductor surface during the diffusion.     

Energy dependence of the quasiparticle lifetime in a 2DES

We present a novel technique for measuring the lifetime of quasiparticle excitations of a 2DES by investigating the tunnelling into a quantum dot from a 2DES over an extended range of energy from the Fermi energy to the sub-band edge. We find that the lifetime τ_qp, of a quasihole excitation, caused by removing an electron from a 2DES state with energy below the Fermi energy E_F, has the form τ_qp=α/, where α is a constant of order unity.