Tag Archives: silicon

Low-Power, High-Performance Tunneling Field Effect Transistors for Advanced Computing

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Summary:

Silicon-based field effect transistor (FET) devices are building blocks of silicon-based digital, analog, and hybrid electronics. Often made of a metal-oxide-silicon (MOS) type structure, these devices are interconnected to generate so-called "complementary" MOSFET circuits, known as CMOS transistor circuitry. CMOS enjoys the benefits of low power and high speed operation, and advancements in these two properties have primarily been achieved through reduction of the channel length, which is now well into the submicron range for commercial devices. However, CMOS technology is approaching certain fundamental limits that will prohibit further miniaturization, likely due to the complex material formulations used. To overcome these limits, researchers at The Ohio State University have developed a novel Tunneling Field Effect Transistor (TFET) that will allow for further device miniaturization, reduced power, and increased speed beyond what is possible with current CMOS technology, while still enabling the use of well-established CMOS manufacturing processes.

Potential Applications:

  • High-performance computing
  • Power-constrained military systems
  • Handheld/miniature electronics
  • Practically anywhere silicon-based electronics are used

Advantages:

  • Extends CMOS, enabling a new generation of device topologies while allowing the use of current manufacturing processes
  • Faster turn-on at lower voltages than competing TFET designs
  • Steep sub-threshold slopes (below 60mV/decade)
  • Less current leakage in the "off" state compared to competing TFET designs
  • Higher current densities in the "on" state compared to competing TFET designs

Advanced High-Efficiency Nanowire LEDs

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Summary:

There is great interest in developing new solid state semiconductor-based light emitting diodes (LEDs) that exhibit new functionality and performance. Principal challenges in creating new semiconductor LED structures include the formation of defects and low doping efficiency, both of which negatively affect device performance. To overcome these challenges, researchers at The Ohio State University have developed new methods and device structures that lead to defect-free, high-efficiency nanowire LEDs. These LEDs can be easily mass manufactured and integrated in silicon electronics, and can hit any bandgap due to the lack of strain relaxation.

Potential Applications:

  • Lighting
  • Laser diodes
  • Photodetectors
  • Communications
  • Sensors

Advantages:

  • Defect-free formation during epitaxial growth
  • Extremely high-efficiency
  • Low resistance
  • Enables simple and broad bandgap engineering
  • Low manufacturing costs and easy integration into Si electronics

Silicon-Based Backward Diodes for Imaging & Radiometry Applications

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Summary:

Passive imaging systems and radiometers require highly sensitive detectors that can operate at millimeter-wave frequencies. Biased Schottky diodes are commonly used for these applications, but the required biasing circuit greatly increases the system and pixel complexity and also leads to extra noise and drift. Zero-bias diode detectors are advantageous because no biasing circuit is required, but they require a large zero bias nonlinearity or curvature. Discrete Ge backward diodes and planar-doped barrier GaAs diodes have previously been used for zero bias detection with high nonlinearity. However, because of the chosen substrates, these devices are not readily suitable for imaging applications, where a mass-producible technology is required to fabricate a large number of identical devices into compact pixilated imaging arrays.

Sb-based heterojunction backwards diodes are also excellent candidates for zero-bias detector applications due to their high sensitivity, high bandwidth, modest temperature dependence, and mass production capability. However, the high cost of Sb-based backward diodes and their incompatibly with mainstream Si read-out circuitry makes them undesirable for cost-sensitive applications and system-level integration.

In order to alleviate these issues, researchers at The Ohio State University have co-developed a Si-based backward diode that is affordable, mass-producible, and can be readily integrated with standard CMOS circuitry. The devices exhibit large zero bias curvature and a low zero biased junction resistance, all at room temperature. The combination of outstanding device performance and compatibility with Si-based electronics makes these devices ideal for highly sensitive imaging and radiometry applications.

Potential Applications:

  • Passive imaging and radiometry systems
  • Screening and detection of concealed weapons
  • Vision enhancement for navigation through obscuring weather

Advantages:

  • High zero-biased curvature, resulting in outstanding sensitivity
  • Low zero-biased junction resistance
  • Compatible with ubiquitous Si-based electronics
  • Low cost and easily mass-producible

Cantilever Couplers for Intra-Chip Coupling to Silicon Photonic Integrated Circuits

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Summary:

As electronics continue to get smaller and faster, standard copper connections between devices will prove to be inadequate for transmitting such high-bandwidth data. A more efficient and high-bandwidth solution is to use photonics, where data is transmitted via light in fiber-optic cables rather than via electrons on a copper wire. Photonic components are expensive, however, and in order to reach mass manufacturing status photonics must somehow be integrated into circuits based on silicon. This is difficult as coupling light directly to silicon integrated circuits has required dicing or cleaving the circuit in some way. Researchers at The Ohio State University have invented a way to efficiently couple light from an optical fiber to silicon photonic integrated circuits at any location on the surface of the circuit without the need to dice or cleave the circuit. This is achieved using on-chip cantilever couplers that can be fabricated using standard CMOS processes used in the semiconductor integrated circuit industry. This technique is an important step towards the widespread realization of optoelectronic devices based on silicon.

Potential Applications:

  • Optical interconnects
  • Low-cost telecommunications
  • Optical Sensors
  • Could revolutionize computing by allowing nearly limitless bandwidth

Advantages:

  • Couples light to silicon photonic ICs without the need to dice or cleave the circuit
  • Efficient and low-loss coupling method
  • Can couple light at any location on the surface of the circuit
  • Cost effective and mass producible as the invention is silicon-based