Quantum well

About: Quantum well is a research topic. Over the lifetime, 44627 publications have been published within this topic receiving 674023 citations. The topic is also known as: QW & quantum potential well.

Solid State Electrically Injected Exciton-Polariton Laser

Abstract: Inversionless ultralow threshold coherent emission, or polariton lasing, can be obtained by spontaneous radiative recombination from a degenerate polariton condensate with nonresonant excitation. Such excitation has, hitherto, been provided by an optical source. Coherent emission from a GaAs-based quantum well microcavity diode with electrical injection is observed here. This is achieved by a combination of modulation doping of the wells, to invoke polariton-electron scattering, and an applied magnetic field in the Faraday geometry to enhance the exciton-polariton saturation density. These measures help to overcome the relaxation bottleneck and to form a macroscopic and degenerate condensate as evidenced by angle-resolved luminescence, light-current characteristics, spatial coherence, and output polarization. The experiments were performed at 30 K with an applied field of 7 T.

Optical properties of InGaN quantum wells

Abstract: The emission mechanisms of strained InGaN quantum wells (QWs) were shown to vary depending on the well thickness L and InN molar fraction x . The QW resonance energy was shifted to lower energy by the quantum confined Stark effect (QCSE) due to the internal piezoelectric field, F PZ . The absorption spectrum was modulated by QCSE and quantum-confined Franz–Keldysh effect (QCFK) for the wells, in which, for the first approximation, the product of F PZ and L (potential drop across the well) exceeds the valence band discontinuity, Δ E V . In this case, dressed holes are confined in the triangular potential well formed at one side of the well. This produces apparent Stokes-like shift (vertical component). The QCFK further modulated the absorption energy for the wells with L greater than the three dimensional free exciton Bohr radius, a B . For the wells having high InN content ( F PZ × L >Δ E V , Δ E C ), electron and hole confined levels drop into the triangular potential wells formed at opposite sides of the wells, which reduces the wavefunction overlap. Doping of Si in the barriers partially screens F PZ resulting in a smaller Stokes-like shift, shorter recombination decay time, and higher emission efficiency. Si-doping was found to improve the interface quality and surface morphology, resulting in an efficient carrier transfer from high to low bandgap energy portions of the well. Effective in-plane localization of carriers in quantum disk size potential minima, which are produced by nonrandom alloy potential fluctuations enhanced by the large bowing parameter and F PZ , produces confined e–h pair whose wavefunctions are still overlapped. Their excitonic features are pronounced provided that L a B and F PZ × L E V (quantized exciton). Several cw laser wafers exhibit stimulated emission from these energy tail states even at room temperature.

Analysis of InGaN-delta-InN quantum wells for light-emitting diodes

Abstract: The design of InGaN-delta-InN quantum wells (QWs) leads to significant redshift for nitride active region with large electron-hole wave function overlap (Γe_hh) and spontaneous emission rate. The analysis was carried out by using self-consistent six-band k⋅p band formalism. The design of active region consisting of 30 A In0.25Ga0.75N QW with InN delta-layer leads to large Γe_hh of >50% with emission wavelength in the yellow and red spectral regimes, which is applicable for nitride-based light-emitting diodes.

Electronic structures of zero-dimensional quantum wells

Abstract: The electronic structures of zero-dimensional quantum wells are studied with a spherical model in the framework of the effective-mass theory. The mixing effect of the heavy and light holes is taken into account, and the symmetry classification and the energy levels of hole states are obtained. The energies of the donor and acceptor states are calculated. The difference between the shallow-impurity states and the eigenstates for the small semiconductor sphere disappears. The selection rules for the optical transition between the conduction- and valence-band states are obtained. The An =0 selection rule is not followed strictly because of the mixing of the L- and (L +2)-orbital wave functions in the wave functions of the hole states. The exciton binding energies are calculated for the small GaAs spheres. The energy levels of the ZnSe spheres are given as functions of the radius and compared with the experiments.

Quantum well structures useful for semiconductor devices

Abstract: A quantum well structure useful for semiconducting devices comprises two barrier regions and a thin epitaxially grown monocrystalline semiconductor material quantum well sandwiched between said barrier regions Each barrier region consists essentially of alternate strain layers forming a superlattice, each of said layers being thinner than said quantum well The layers are so thin that no defects are generated as a result of the release of stored strain energy