7,597 research outputs found
Locality and topology in the molecular Aharonov-Bohm effect
It is shown that the molecular Aharonov-Bohm effect is neither nonlocal nor
topological in the sense of the standard magnetic Aharonov-Bohm effect. It is
further argued that there is a close relationship between the molecular
Aharonov-Bohm effect and the Aharonov-Casher effect for an electrically neutral
spin particle encircling a line of charge.Comment: 3 pages, no figure
The Born-Oppenheimer Approach to the Matter-Gravity System and Unitarity
The Born-Oppenheimer approach to the matter-gravity system is illustrated and
the unitary evolution for matter, in the absence of phenomena such as
tunnelling or other instabilities, verified. The Born-Oppenheimer approach to
the matter-gravity system is illustrated in a simple minisuperspace model and
the corrections to quantum field theory on a semiclassical background
exhibited. Within such a context the unitary evolution for matter, in the
absence of phenomena such as tunnelling or other instabilities, is verified and
compared with the results of other approaches. Lastly the simplifications
associated with the use of adiabatic invariants to obtain the solution of the
explicitly time dependent evolution equation for matter are evidenced.Comment: Latex, 12 pages. Revised version as accepted for publication by
Class. and Quant. Grav. Some points explained and misprints correcte
Experimental Determination of E−k Relationship in Electron Tunneling
We report here measurements of electron
tunneling through thin AlN films in which the
imaginary component of the propagation vector
in the forbidden band has been determined as
a function of energy from the dependence of
the tunneling current upon insulator thickness.
The relationship so derived agrees well with
Franz's empirical relationship for a material
with the 4.2-eV forbidden-band energy of AlN.
These results allow the prediction of voltage-current
characteristics over the entire range
of experimental variables with no arbitrary
adjustable parameters, and also subject to several
internal self-consistency checks. In each
case complete consistency is observed, To
the authors' knowledge, this represents the
first unambiguous demonstration of such consistency
in thin-film tunneling
Energy-Momentum Relationship in InAs
We have performed surface-barrier tunneling measurements on p-type InAs and found the energy dependence of the wave vector in the forbidden gap to be in agreement with Franz's relationship based on a two-band model
Tunneling in CdTe Schottky Barriers
The tunneling characteristics of metal contacts on n−CdTe have been measured. Both the forward- and reverse-bias characteristics are in good agreement with the two-band model for the energy-complex-momentum relationship. The presence of trapping states increased the magnitude of the tunneling current at low levels by providing a two-step transition. The slope of the forward-bias log_e J−versus−V curves for tunneling through the intermediate states was reduced by a factor of 2
Fermi Level Position at Semiconductor Surfaces
There have been several recent reports of barrier height studies on metal-semiconductor interfaces. Metals of widely different work functions evaporated onto Si and GaAs surfaces indicated that in each case the energy difference
between the semiconductor conduction band edge
and Fermi level at the interface,φ_(Bn), was essentially
independent of the metal, which indicates
that the Fermi level is fixed by surface
states. In the present work barrier height measurements
have been made on a number of zinc-blende semiconductors to determine (a) if the barriers are in all cases determined by surface states, and (b) the relation between the Fermi
energy at the interface and the band gap E_g
Conduction Band Minima in AlAs and AlSb
The photoresponse of surface barrier rectifiers made by evaporating a metal such as gold or platinum on a cleaved surface of AlAs and AlSb has been measured in the front wall configuration. The photoresponse of such units for hv > E_g, where E_g is the energy gap, will be proportional to the absorption coefficient as long as the optical attenuation length is large compared to both the width
of the space-charge region and the minority carrier
diffusion length. The analysis is essentially
the same as that for p-n junctions with the exception
that the barrier is at the surface and hence
more sensitive to photons of high absorption coefficient.
Photoinjection of carriers from the metal into the semiconductor for photon energies where hv < E_g can also be observed
Voltage Dependence of Barrier Height in AIN Tunnel Junctions
We report measurements of barrier heights on
AI-AIN-Mg thin-film structures as a function of
applied voltage and insulator thickness. These results
are in disagreement with currently accepted
theories based upon image potential and/or field
penetration of the electrodes
The Effect of Trapping States on Tunneling in Metal Semiconductor Junctions
The tunneling behavior of Schottky barriers has been investigated by several authors. The I-V characteristics exhibit an exponential form in the forward direction which can be used to determine the energy vs complex momentum dispersion relation for charge carriers in the forbidden
gap. In this paper we show that under proper conditions the presence of traps can increase the tunneling probability and result in a reduction in the slope of the log I vs V characteristic by a factor of 2
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