Single-hole transistor in p-type GaAs/AlGaAs heterostructures (original) (raw)
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Observation of excited states in a p-type GaAs quantum dot
EPL (Europhysics Letters), 2008
A quantum dot fabricated by scanning probe oxidation lithography on a p-type, C-doped GaAs/AlGaAs heterostructure is investigated by low temperature electrical conductance measurements. Clear Coulomb blockade oscillations are observed and analyzed in terms of sequential tunneling through the single-particle levels of the dot at T hole = 185 mK. The charging energies as large as ∼ 2 meV evaluated from Coulomb diamond measurements together with the well resolved single-hole excited state lines in the charge stability diagram indicate that the dot is operated with a small number of confined particles close to the ultimate single-hole regime.
Electron and hole spin dynamics in semiconductor quantum dots
We report direct measurement of the spin dynamics of electrons and holes in self-assembled InAs quantum dots ͑QDs͒ through polarization-sensitive time-resolved photoluminescence experiments on modulation-doped quantum dot heterostructures. Our measured hole spin decay time is considerably longer than in bulk and quantum well semiconductor systems, indicating that the removal of near degenerate hole states with different spin quantization axes through three-dimensional confinement slows hole spin relaxation in semiconductors. The electron and hole spin decay times we observe ͑electrons: 120 ps; holes: 29 ps͒ are consistent with spin relaxation via phonon-mediated virtual scattering between the lowest two confined levels in the QDs, which have a mixed spin character due to the spin-orbit interaction.
Spin dynamics of electrons and holes in p-doped InAs/GaAs quantum dots
Brazilian Journal of Physics, 2006
We have investigated the electron and hole spin dynamics in p-doped semiconductor InAs/GaAs quantum dots by time resolved photoluminescence. We observe a decay of the average electron spin polarisation down to 1/3 of its initial value with a characteristic time of T ∆ ≈ 500ps. We attribute this decay to the hyperfine interaction of the electron spin with randomly orientated nuclear spins. Magnetic field dependent studies reveal that this efficient spin relaxation mechanism can be suppressed by a field of the order of 100mT. In pump-probe like experiments we demonstrate that the resident hole spin, "written" with a first pulse, remains stable long enough to be "read" 15ns later with a second pulse.
hole nuclear spin interactions in quantum dots
We have measured the carrier spin dynamics in p-doped InAs=GaAs quantum dots by pump-probe and time-resolved photoluminescence experiments. We obtained experimental evidence of the hyperfine interaction between hole and nuclear spins. In the absence of an external magnetic field, our calculations based on dipole-dipole coupling between the hole and the quantum dot nuclei lead to a hole-spin dephasing time for an ensemble of dots of 14 ns, in close agreement with experiments.
Electrically tunable effective g-factor of a single hole in a lateral GaAs/AlGaAs quantum dot
Communications Physics
Electrical tunability of the g$$g-factor of a confined spin is a long-time goal of the spin qubit field. Here we utilize the electric dipole spin resonance (EDSR) to demonstrate it in a gated GaAs double-dot device confining a hole. This tunability is a consequence of the strong spin-orbit interaction (SOI) in the GaAs valence band. The SOI enables a spin-flip interdot tunneling, which, in combination with the simple spin-conserving charge transport leads to the formation of tunable hybrid spin-orbit molecular states. EDSR is used to demonstrate that the gap separating the two lowest energy states changes its character from a charge-like to a spin-like excitation as a function of interdot detuning or magnetic field. In the spin-like regime, the gap can be characterized by the effective g$$g-factor, which differs from the bulk value owing to spin-charge hybridization, and can be tuned smoothly and sensitively by gate voltages.
Hole-Nuclear Spin Interaction in Quantum Dots
Physical Review Letters, 2009
We have measured the carrier spin dynamics in p-doped InAs/GaAs quantum dots by pump-probe photo-induced circular dichroism and time-resolved photoluminescence experiments. We show that the hole spin dephasing is controlled by the hyperfine interaction between hole and nuclear spins. In the absence of external magnetic field, we find a characteristic hole spin dephasing time of 15 ns, in close agreement with our calculations based on dipole-dipole coupling between the hole and the quantum dot nuclei. Finally we demonstrate that a small external magnetic field, typically 10 mT instead of 200 mT for the case of electrons, quenches the hyperfine hole spin dephasing.
MRS Proceedings, 2009
The spin dynamics of resident holes in singly p-doped InAs/GaAs quantum dots is studied by pump-probe photo-induced circular dichroism experiments. We show that the hole spin dephasing is controlled by the hyperfine interaction between the hole spin and nuclear spins. We find a characteristic hole spin dephasing time of 12 ns, in close agreement with our calculations based on a dipole-dipole coupling between the hole and the quantum dot nuclei. Finally we demonstrate that a small external magnetic field, typically 10 mT, quenches the hyperfine hole spin dephasing.
Electronic dynamics due to exchange interaction with holes in GaAs
Ultrafast Phenomena in Semiconductors and Nanostructure Materials XIV, 2010
We present an investigation of electron-spin dynamics in p-doped bulk GaAs due to the electron-hole exchange interaction, aka the Bir-Aronov-Pikus mechanism. We discuss under which conditions a spin relaxation times for this mechanism is, in principle, accessible to experimental techniques, in particular to 2-photon photoemission, but also Faraday/Kerr effect measurements. We give numerical results for the spin relaxation time for a range of p-doping densities and temperatures. We then go beyond the relaxation time approximation and calculate numerically the spin-dependent electron dynamics by including the spin-flip electron-hole exchange scattering and spin-conserving carrier Coulomb scattering at the level of Boltzmann scattering integrals. We show that the electronic dynamics deviates from the simple spin-relaxation dynamics for electrons excited at high energies where the thermalization does not take place faster than the spin relaxation time. We also present a derivation of the influence of screening on the electron-hole exchange scattering and conclude that it can be neglected for the case of GaAs, but may become important for narrow-gap semiconductors.
Hole-spin initialization and relaxation times in InAs/GaAs quantum dots
Physical Review B, 2011
We study, at low temperature and zero magnetic field, the hole-spin dynamics in InAs/GaAs quantum dots. We measure the hole-spin relaxation time at a time scale longer than the dephasing time (about ten nanoseconds), imposed by the hole-nuclear hyperfine coupling. We use a pump-probe configuration and compare two experimental techniques based on differential absorption. The first one works in the time domain, and the second one is a new experimental method, the dark-bright time-scanning spectroscopy (DTS), working in the frequency domain. The measured hole-spin relaxation times, using these two techniques, are very similar, in the order of TNh≈1 μs. It is mainly imposed by the inhomogeneous hole hyperfine coupling in the hole localization volume. The DTS technique allows us also to measure the hole-spin initialization time τi. The hole spin is initialized by a periodic train of circularly polarized pulses at 76 MHz; we have observed that τi decreases as the power density increases, and we have measured a minimum value of τi≈100 ns in good agreement with a simple model [see B. Eble, P. Desfonds, F. Fras, F. Bernardot, C. Testelin, M. Chamarro, A. Miard, and A. Lemaître, Phys. Rev. BPLRBAQ1098-012110.1103/PhysRevB.81.045322 81, 045322 (2010)].
Hole-hole and electron-hole exchange interactions in single InAs/GaAs quantum dots
Physical Review B, 2009
A combined analysis of microphotoluminescence ͑PL͒ and microphotoluminescence excitation ͑PLE͒ spectra of the same single quantum dot ͑QD͒ enables an unambiguous identification of four sharp resonances in the excitation spectrum detected on the positive trion transition ͑h 0 → e 0 h 0 h 1 ͒ and reveals the complete fine structure of the hot trion. Transitions into states normally forbidden by ͑spin͒ selection rules for optical transitions between pure spin states are observed. The splittings of all triplet states are found to be large ͑up to 3 meV͒, asymmetric, and QD size and shape dependent. The experimental data are in excellent agreement with theoretical calculations in the framework of eight-band k • p theory and the configuration-interaction method. To account for the physical effects which lead to the observed fine-structure splitting, parts of the complex model are successively omitted. This approach identifies the anisotropic hole-hole exchange interaction as well as correlation effects dominating the observed fine-structure splitting of the hot trion.