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

A calculation of dynamical conductivity is performed for low-dimensional systems, by taking into account the screening of field. Our calculation is valid for all value of wave vector and frequency. The Drude conductivity of three, two and one-dimensional free electron gas, layered electron gas and quantum wire system can be deduced from our calculation. However, our calculation suggests that the use of Drude formulae of conductivity to explain experimental result on microwave and infra-red conductivity, in long wave length limit, can be highly erroneous in case of low-dimensional system that offer larger value of relaxation time. It is found that; (i) screening of a dynamical field becomes less significant on reduction in dimensionality and (ii) unlike the case of three dimensional electron gas, transverse electric field cannot excite collective excitation modes (penetration depth cannot be defined) in a two-dimensional electron gas and quantum wire system. In comparison with prior reported calculation ours is more rigorous calculation as it includes the possibility of propagation of collective excitation modes in all direction. The plasmons in a low-dimensional system cannot be excited for negligibly small value of momentum transfer.

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MAN-MADE LOW-DIMENSIONAL SOLIDS: NEW CHALLENGES IN MICROSTRUCTURE MATERIALS SCIENCE

International Journal of Modern Physics B ◽

10.1142/s0217979293003024 ◽

1993 ◽

Vol 07 (15) ◽

pp. 2743-2778 ◽

Cited By ~ 12

Author(s):

RICHARD NÖTZEL ◽

KLAUS H. PLOOG

Keyword(s):

Quantum Dot ◽

Electronic Properties ◽

Quantum Wire ◽

Materials Science ◽

Three Dimensions ◽

Novel Device ◽

Semiconductor Structures ◽

Device Applications ◽

Gaas Quantum Dot ◽

Low Dimensional

Size quantization in man-made semiconductor structures of less than three-dimensions leads to exciting new electronic properties which are important for fundamental physics and for development of novel device concepts. Fundamental research as well as device applications based on these low-dimensional semiconductor structures require methods to fabricate the structures and to control their geometrical size on the nanometer scale in a reproducible manner. We introduce a new concept to directly synthesize III-V semiconductor quantum-wire and quantum-dot structures. The concept is based on the evolution of well ordered macrosteps (facets) on non-(100)-oriented GaAs surfaces during molecular beam epitaxy which allows us to produce arrays of alternating narrow and wide regions of GaAs in an AIAs matrix. This arrangement forms symmetric and asymmetric GaAs quantum-dot structures on (111) and (211) surfaces, respectively, and quantum-wire structures on (311) substrates. The accumulation of steps by step bunching on (210) GaAs makes possible the fabrication of mesoscopic step arrays in GaAs/AlAs multilayer structures having a periodicity of 230 Å. This periodicity is comparable to the exciton Bohr radius and thus of particular importance for the modulation of the electronic properties of GaAs based heterostructures. The existence of all these quantum-wire and quantum-dot structures is confirmed by high-resolution transmission-electron microscopy and atomic-force microscopy. The quantum confinement of carriers is revealed by the distinct electronic properties.

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Strain measurement in In0.2Ga0.8As/GaAs quantum wires by convergent beam electron diffraction

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100138592 ◽

1995 ◽

Vol 53 ◽

pp. 444-445

Author(s):

S. Hillyard ◽

Y.-P. Chen ◽

J.D. Reed ◽

W.J. Schaff ◽

L.F. Eastman ◽

...

Keyword(s):

Electron Diffraction ◽

Semiconductor Lasers ◽

Quantum Wire ◽

Quantum Wires ◽

Convergent Beam Electron Diffraction ◽

Zero Order ◽

Beam Electron ◽

Local Lattice ◽

Device Applications ◽

Convergent Beam

The positions of high-order Laue zone (HOLZ) lines in the zero order disc of convergent beam electron diffraction (CBED) patterns are extremely sensitive to local lattice parameters. With proper care, these can be measured to a level of one part in 104 in nanometer sized areas. Recent upgrades to the Cornell UHV STEM have made energy filtered CBED possible with a slow scan CCD, and this technique has been applied to the measurement of strain in In0.2Ga0.8 As wires.Semiconductor quantum wire structures have attracted much interest for potential device applications. For example, semiconductor lasers with quantum wires should exhibit an improvement in performance over quantum well counterparts. Strained quantum wires are expected to have even better performance. However, not much is known about the true behavior of strain in actual structures, a parameter critical to their performance.

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