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Optical Back-Gate Semiconductors Disclosure Number: IPCOM000198807D
Publication Date: 2010-Aug-17
Document File: 3 page(s) / 41K

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The Prior Art Database


Disclosed is a an approach to increasing the power efficiency of semiconductor systems using Optical Back-Gate semiconductors as a means of controlling device threshold voltages and energy consumption.

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Optical Back-Gate Semiconductors

The following issues relate to the power efficiency of semiconductor systems:

Denser semiconductors drive higher leakage and power consumption.

Power requirements are beginning to limit system performance.

Thermal management is driving high-end systems back to water cooled solutions.

The solution described addresses the listed issues using optical Optical Back-Gate (OBG) Semiconductors.

Light at certain frequencies of the infrared (IR) impinges upon the depletion region of the active circuit when it is shown from the back side of a semiconducting device, such as a metal-oxide semiconductor field-effect transistor (MOSFET) or Power MOSFET, and travels thru the bulk silicon phase (either guided or non-guided) to the active device plane. This decreases the applied voltage required to invert a semiconducting layer, and in turn reduces the overall semiconductor power and on-time latency (creation of an optical back-gate). Modulated light promotes faster turn-on and turn-off times. The invention designs the OBG semiconductor device with very low Vts and uses the modulated light (as a back gate) to switch gates. The invention has the potential to be guided/localized light limited to select gates or could be global, as in a global synchronous clock.

The photovoltaic effect of the OBGs generates free carriers (in the conduction band) according to the formula:

EQ 1 G(x) =P0ae-ax (where P is the photon flux density entering the distal aspect of the gate's depletion region, and a is the absorption coefficient)

Thus, the more light energy of the appropriate wavelength for free carrier absorption (e.g., selective wrt holes and electrons) impinging the depletion region, the more free carriers generated in that region, and the more sensitive and responsive the heterojunction is to small switching voltages. Engineers can design several other key semiconducting parameters using light, such as the index of refraction and the band-gap. The figure below shows an embodiment of guided and non-guided OBG semiconducting complementary metal-oxide semiconductor (CMOS). Bipolar CMOS, MOSFETS, Silicon-Germanium (SiGe) and ot...