A Cooper pair light emitting diode

We demonstrate Cooper-pair's drastic enhancement effect on band-to-band radiative recombination in a semiconductor. Electron Cooper pairs injected from a superconducting electrode into an active layer by the proximity effect recombine with holes injected from a p-type electrode and dramatically accelerate the photon generation rates of a light emitting diode in the optical-fiber communication band. Cooper pairs are the condensation of electrons at a spin-singlet quantum state and this condensation leads to the observed enhancement of the electric-dipole transitions. Our results indicate the possibility to open up new interdisciplinary fields between superconductivity and optoelectronics.Comment: 5 pages (4 figures

Transport properties of nitrogen doped p‐gallium selenide single crystals

Nitrogen doped gallium selenide single crystals are studied through Hall effect and photoluminescence measurements in the temperature ranges from 150 to 700 K and from 30 to 45 K, respectively. The doping effect of nitrogen is established and room temperature resistivities as low as 20 Ω cm are measured. The temperature dependence of the hole concentration can be explained through a single acceptor‐single donor model, the acceptor ionization energy being 210 meV, with a very low compensation rate. The high quality of nitrogen doped GaSe single crystals is confirmed by photoluminescence spectra exhibiting only exciton related peaks. Two phonon scattering mechanisms must be considered in order to give quantitative account of the temperature dependence of the hole mobility: scattering by 16.7 meV A′1 homopolar optical phonons with a hole‐phonon coupling constant g2=0.115 and scattering by 31.5 meV LO polar phonon with a hole Fröhlich constant αh⊥[email protected]

Two-photon interference and coherent control of single InAs quantum dot emissions in an Ag-embedded structure

We have recently reported the successful fabrication of bright single-photon sources based on Ag-embedded nanocone structures that incorporate InAs quantum dots. The source had a photon collection efficiency as high as 24.6%. Here we show the results of various types of photonic characterizations of the Ag-embedded nanocone structures that confirm their versatility as regards a broad range of quantum optical applications. We measure the first-order autocorrelation function to evaluate the coherence time of emitted photons, and the second-order correlation function, which reveals the strong suppression of multiple photon generation. The high indistinguishability of emitted photons is shown by the Hong-Ou-Mandel-type two-photon interference. With quasi-resonant excitation, coherent population flopping is demonstrated through Rabi oscillations. Extremely high single-photon purity with a $g^{(2)}$(0) value of 0.008 is achieved with $\pi$-pulse quasi-resonant excitation.Comment: 15 pages, 6 figure

Hysteretic magnetoresistance and thermal bistability in a magnetic two-dimensional hole system

Colossal negative magnetoresistance and the associated field-induced insulator-to-metal transition, the most characteristic features of magnetic semiconductors, are observed in n-type rare earth oxides and chalcogenides, p-type manganites, n-type and p-type diluted magnetic semiconductors (DMS) as well as in quantum wells of n-type DMS. Here, we report on magnetostransport studies of Mn modulation-doped InAs quantum wells, which reveal a magnetic field driven and bias voltage dependent insulator-to-metal transition with abrupt and hysteretic changes of resistance over several orders of magnitude. These phenomena coexist with the quantised Hall effect in high magnetic fields. We show that the exchange coupling between a hole and the parent Mn acceptor produces a magnetic anisotropy barrier that shifts the spin relaxation time of the bound hole to a 100 s range in compressively strained quantum wells. This bistability of the individual Mn acceptors explains the hysteretic behaviour while opening prospects for information storing and processing. At high bias voltage another bistability, caused by the overheating of electrons10, gives rise to abrupt resistance jumps

Stability of multi-component epilayers and nanopattern formation

A uniform multi-component epilayer may lose stability under the combined action of spinodal decomposition and epilayer–substrate interaction, separating into multiple phases. The phases may further self-organize into regular patterns. This paper investigates the compositional stability of a ternary epliayer and the subsequent emergence of nanoscale patterns. Multiple energetic forces and kinetic processes involving phase separation, phase coarsening and phase refining are incorporated into a continuous phase field model. Linear stability analysis is performed by perturbing a uniform concentration field into a sinusoidal field with small amplitude and arbitrary wavelength. The analysis shows that the epilayer–substrate interaction counteracts the coarsening effect of phase boundary energy and may lead to the formation of steady nanoscale patterns. Detailed analysis also reveals the interaction of multi-phases and its effect on the stability condition. Numerical simulation of evolving concentration field is discussed at the end of the paper. The simulations show that the pattern formation process of multi-component epilayers involves remarkably rich dynamics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43296/1/11051_2004_Article_3304.pd

Anisotropic Lattice Deformation of InAs Self-Assembled Quantum Dots Embedded in GaNAs Strain Compensating Layers

Lattice deformations of InAs self-assembled quantum dots, which were grown on (001)GaAs substrates and embedded in GaNAs strain compensating layers (SCLs), were examined with an ion-channeling method in Rutherford backscattering spectrometry. The channeling experiments demonstrated that the increase of the nitrogen concentrations in the GaNAs SCLs caused the indium lattice displacements along the [001] growth direction while those parallel to the (001) crystal plane were kept unchanged