Plasma Wave Electronics
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DESCRIPTION
a. Background. Operation of conventional transistors. Over 95% of transistors today are so-called field effect transistors. In these devices, two contacts are separated by the device channel. These contacts are called the source and the drain. These contacts contain lots and lots of electrons. The third contact is isolated from the channel butsituated very close to it. This third contact is called "the gate". Electrons are negatively charged and are attracted to a positive charge. Hence, when we apply positive voltage to the gate, electrons rush into the channel and connect the source and the drain. This is the ON-state. When the gate voltage is more negative (or zero), we have no electrons in the channel. This is the OFF-state. These two states are 1 and 0 of modern computers. A standard way to describe electrons in the transistor channel is to imagine that they form a gas. This gas is called two-dimensional (2D), since the electrons in their desire to come as close as possible to the positive gate potential are situated in a very thin layer in the channel at the boundary with the gate insulator that prevents them from going to the gate
b. Our new approach. In our Phys. Rev. Lett. paper with Professor Dyakonov published in 1993, we pointed out that in modern devices the electron density in the channel is so large that they very often collide with each other. No longer they form a 2D-gas. Rather they form a 2D fluid. The equations describing this fluid are the same equations that describe shallow water. Waves can propagate in this fluid. These waves are called plasma waves, and they are completely analogous to the waves in a shallow water channel. Moreover, even though the electron 2D fluid is not a gas, these plasma waves are very similar to sound waves even though their velocity is thousand times higher.
HEMT PROTOTYPE.
A short channel High Electron Mobility Transistor (HEMT) has a resonance response to electromagnetic radiation at the plasma oscillation frequencies of the two dimensional electrons in the device. The devices, which use this resonance response should operate at much higher frequencies than conventional, transit-time limited devices, since the plasma waves propagate much faster than electrons. The responsivities of such devices may greatly exceed the responsivities of Schottky diodes currently used as detectors and mixers in the terahertz range. A long channel HEMT has a non-resonant response to electromagnetic radiation and can be used as a broad band detector for frequencies up to several tens of terahertz. Recently, a prototype non-resonant detector (operating in the microwave range) was fabricated using an AlGaAs/GaAs 0.15 micron gate HEMT. The measured dependencies of the detector responsivity on the gate bias and frequency are in good agreement with our theory.
APPLICATIONS.
The plasma wave electronics device that we proposed include an oscillator, a mixer, a frequency multiplier, an array that we called "an electronic flute" (since its operation is very similar to that
of a conventional flute), and a detector. So far, we have only demonstrated a detector so far and only at relatively low frequencies. At high frequencies (i. e. in the terahertz range, on the order of 10^12 Hz), the predicted sensitivity of such a detector should be thousand or more times larger than the sensitivity of conventional detectors. This should open up many applications, including the detection of explosives or poisonous substances, control of environment, industrial controls, certain defense applications, applications in radioastronomy, etc. Another plasma wave electronics device that may be commercialized relatively soon is an "electronic flute".
Publications on
Plasma wave Electronics
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