1,721,121 research outputs found
Preface [17th International Conference on Electronic Properties of Two-Dimensional Systems]
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13th International Conference on Modulated Semiconductor Structures
No full textProceedings 13th International Conference on Modulated Semiconductor Structure
Surface confined phonons in semiconductor superlattices
No full textWe show that the phonon spectra of finite GaAs/AIAs(001) superlattices along their growth direction display a new type of confined surface modes which split off the superlattice confined optical branches. Their frequency location and decay inside the superlattice is investigated by means of a model calculation and compared with the behaviour of surface states of semi-infinite GaAs
Saturation and bistability of defect-mode intersubband polaritons
Full text linkIn this paper we report about linear and nonlinear optical properties of intersubband cavity polariton samples, where the resonant photonic mode is a defect state in a metallodielectric photonic crystal slab. By tuning a single geometric parameter of the resonator, the cavity Q factor can reach values as large as 85, with a consequent large cooperativity for the light-matter interaction. We show that a device featuring large cooperativity leads to sharp saturation, or even bistability, of the polariton states. This nonlinear dynamics occurs at the crossover between the weak-and the strong-coupling regimes, where the weak critical coupling concept plays a fundamental role
Manipulation of Electron Orbitals in Hard-Wall InAs/InP Nanowire Quantum Dots
No full textWe present a novel technique for the manipulation of the energy spectrum of hard-wall InAs/InP nanowire quantum dots. By using two local gate electrodes, we induce a strong transverse electric field in the dot and demonstrate the controlled modification of its electronic orbitals. Our approach allows us to dramatically enhance the single-particle energy spacing between the first two quantum levels in the dot and thus to increment the working temperature of our InAs/InP single-electron transistors. Our devices display a very robust modulation of the conductance even at liquid nitrogen temperature, while allowing an ultimate control of the electron filling down to the last free carrier. Potential further applications of the technique to time-resolved spin manipulation are also discussed
Growth of defect-free GaP nanowires
Full text linkThe crystal structure of GaP nanowires grown by Au-assisted chemical beam epitaxy was investigated as a function of group V flux and growth temperature. By increasing the tertiarybutyl phosphine flux we obtained nanowires with a stacking defect-free wurtzite crystal structure. Variation of growth temperature also had a profound impact on the crystal structure. Lowering the growth temperature from 600 to 560 °C and keeping constant both triethylgallium and tertiarybutyl phosphine precursor fluxes, the crystal structure of GaP NWs was drastically improved from a highly defective intergrowth of zinc-blende and wurtzite to a wurtzite crystal structure free of stacking defects. These results are compared to current literature on GaP NW growth, and we suggest that the low V/III ratio is the key ingredient for the high crystal quality of our GaP nanowires
Scattering mechanisms in undoped In0.75Ga0.25As/In0.75Al0.25As two- dimensional electron gases
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Electrostatic spin control in multi-barrier nanowires
No full textWe demonstrate that a consistent breakdown of the standard even–odd filling scheme in the Coulomb blockade regime can be easily obtained in a quantum dot containing two wells strongly coupled by a very transparent barrier. By exploiting a multi-gate configuration, we prove that a partial filling of nearly degenerate orbitals can be controlled electrostatically. Singlet–triplet spin transitions are demonstrated by low-temperature magneto-transport measurements
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