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| Inverted-design optical microscope |
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| Semiconductor laser |
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| Sun heat radiation sensor |
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| Photochromic naphthopyrans |
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| UV-A, UV-B discrimination sensor |
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| Thin film transistor |
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Apparatus comprising refractive means for elections
| Details |
Inventors: Baldwin, Kirk W.; Pfeiffer, Loren N.; Spector, Joseph; Stormer, Horst L.; West, Kenneth W.;
Assignee: AT&T Bell Laboratories (Murray Hill, NJ)
Primary Examiner: James; Andrew J.
Assistant Examiner: Crane; Sara W.
Attorney, Agent or Firm: Pacher; E. E.
The disclosed novel solid state electronic devices comprise a two-dimensional electron gas (2DEG), emission means of ballistic 2DEG electrons, collection means of 2DEG electrons, and control means disposed between the emissions means and the collection means such that ballistic 2DEG electrons that travel from the emission means to the collections means pass through a portion of the device that underlies the control means. By means of the control means the electron density in the portion of the device can be changed, whereby the path of ballistic 2DEG electrons can be affected, in a manner analogous to refraction in optics. This "electron refraction" makes possible a variety of devices, e.g., switches and logic elements. |
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DETAILED DESCRIPTION OF SOME EXEMPLARY EMBODIMENTS Before describing some currently preferred embodiments we will derive expressions describing the effect of a potential step on the propagation of a ballistic electron in a 2 DEG.
An electron of wave vector k and kinetic energy ##EQU1## traversing an extended potential .
DELTA.
V changes its kinetic energy to ##EQU2## In these expressions h is Planck's constant divided by 2.
pi.
, and m* is the effective electron mass in the material.
Translational invariance along the step preserves the parallel component of electron momentum and thus k sin .
theta.
=k' sin .
theta.
', with the angles .
theta.
and .
theta.
' defined in FIG.
1.
This equation can be expressed as ##EQU3## which resembles Snell's law in optics.
The reflection coefficient ##EQU4## and transmission coefficient ##EQU5## can be similarly derived by calculating the probability current for the different components and requiring continuity of the wave function and its derivative at the interface.
All these equations are analogous to the optical case if one defines the square root of the electron kinetic energy as being proportional to an effective index of refraction.
In a degenerate system such a definition becomes quite meaningful since all relevant electrons have the same kinetic energy E.
sub.
f =h.
sup.
2 k.
sub.
f.
sup.
2 /2 m*, the Fermi energy.
At an abrupt interface separating regions of different electron density, the relevant kinetic energy changes from E.
sub.
f to E'.
sub.
f.
The refracting power of such an abrupt density step is determined simply by the ratio of the adjacent Fermi energies, E.
sub.
f to E'.
sub.
f.
In 2 D electron systems abrupt steps in density can be readily created via electrostatic gates in close proximity to the 2 D channel.
The edge of such a gate acts as the refractive perimeter whose refracting power is controllable by the gate voltage.
Furthermore, since in 2 D the carrier density n and E.
sub.
f are related by the equation ##EQU6## Snell's law translates into ##EQU7## with n and n' denoting the density surrounding the gate and beneath the gate, respectively
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Quantum Computing 
