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Your search keyword '"Pfeiffer, L. N."' showing total 28 results
Start Over Author "Pfeiffer, L. N." Publication Type Books
28 results on '"Pfeiffer, L. N."'

19. Ballistic Electron Optics

Author

Spector, J., primary, Weiner, J. S., additional, Stormer, H. L., additional, Baldwin, K. W., additional, Pfeiffer, L. N., additional, and West, K. W., additional

Published
1992
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27. Anisotropic state of two-dimensional electron gas in high Landau levels.

Author

Kramer, Bernhard, Lilly, M. P., Cooper, K. B., Eisenstein, J. P., Pfeiffer, L. N., West, K. W., Wegscheider, W., and Bichler, M.

Abstract

When several Landau levels of a high mobility two-dimensional electron system are occupied, transport measurements reveal evidence for intriguing new phenomena at low temperature. Near half filling in the N=2 and higher spin-split Landau levels, dramatic resistance anisotropies are observed. Large magnetoresistance peaks form in one direction in the 2D plane while deep minima form in the in the orthogonal direction. Application of a parallel magnetic field can re-orient this anisotropy. Interestingly, in the N=1 Landau level, parallel fields not only suppress the energy gap of the ν=5/2 fractional quantum Hall state but also render the transport highly anisotropic. [ABSTRACT FROM AUTHOR]

Published
2000
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28. GaAs/AlGaAs quantum wire lasers and other low-dimensional structures fabricated by cleaved edge overgrowth.

Author

Helbig, Reinhard, Wegscheider, W., Pfeiffer, L. N., and West, K. W.

Abstract

Cleaved edge overgrowth—a molecular beam epitaxy technique which incorporates two sequential growth steps along orthogonal crystal directions —was employed to fabricate lasers containing an array of 22 quantum wires with cross-sections of about 7 by 7 nm. In addition, we have applied this method to prepare single modulation-doped quantum wires exhibiting electron mobilities in excess of 2×105 cm2/Vs. The active region of the lasers consists of atomically precise quantum wires that form at the T-shaped intersections of [001] oriented quantum wells with those grown, after an in situ cleave, along the [110] crystal axis. The origin of the quantum mechanical bound state is the relaxation of quantum well confinement at this intersection, which leads to an expansion of the electron and hole wavefunctions into the larger available volume at the T-junction. The quantum wires are, in turn, embedded in a T-shaped dielectric waveguide formed by [001] and [110] oriented cladding layers, which confine the optical mode to the vicinity of the one-dimensional quantum structures. The high degree of structural perfection achievable in this way allows the observation of stimulated optical emission in optically as well as in electrically pumped devices. Efficient current injection into the wires by p and n doping in the two growth directions is demonstrated by the suppression of optical emission from the quantum well states as well as by threshold currents as low as 400 μA for uncoated devices at 1.7 K. From the absence of bandgap renormalization effects manifested in the near constancy of the quantum wire emission wavelength with changes in pump power over almost three orders of magnitude, we conclude that the Mott density for ionization of the one-dimensional excitons is never reached. This suggests that gain in these lasers is due to exciton recombination and indicates interesting new behavior of exciton in low-dimensional systems. In two-terminal magnetoresistance measurements along the modulation-doped quantum wires we see clear evidence for two-dimensional confinement of the electrons. The observed retarded depopulation of Landau levels at low magnetic fields is in close agreement with a calculation of the magnetic field dependence of the number of occupied subbands in a narrow channel. [ABSTRACT FROM AUTHOR]

Published
1995
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