Tag Archives: circuit

Resonant Interband Tunneling Diodes–Extending Moore’s Law and Enabling New Circuitry

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Summary:

Since the early 1960’s, the utility of the tunnel diode (or Esaki diode) has been evident, but several practical hurdles have kept it from reaching mainstream status. Historically, it has been difficult to control peak current and, more importantly, tunnel diode fabrication has lacked a Si-based process that can easily be mass produced and integrated into existing Si-based integrated circuits. As a result, today’s tunnel diodes are primarily used in discrete form and for niche applications. Regardless, tunnel diodes have many current and future applications, and the challenges of aggressively scaled CMOS is forcing this subject to be seriously revisited, since quantum tunneling will dominate in any ultra-low dimensional material. The structure of the Resonant Interband Tunneling Diode (RITD) differs from that of the Esaki diode (traditional tunnel diode) which results in additional useful properties. In RITDs, electrons quantum mechanically tunnel across an energy well formed between two barriers, where Esaki diodes have no energy well. This quantum mechanical tunneling effect happens extremely quickly and thus very high speed electronics can be realized with the use of RITDs. Terahertz operation has been demonstrated. Furthermore, a useful effect called Negative Differential Resistance (NDR) can be exploited using these devices.

Potential Applications:

  • Can augment CMOS technology resulting in novel logic and embedded circuit topologies with reduced device count, low power, and faster speed.
  • Can be implemented in ICs, memory devices, and small, lightweight portable electronics for greater performance at lower power consumption
  • Applications found in oscillators, frequency locking circuits, advanced SRAM circuits, highly integrated A/D converters, high speed digital latches, and many others

Advantages:

  • Uses quantum tunneling, a very high-speed process. Terahertz operation has been demonstrated
  • Shown to exhibit Negative Differential Resistance (NDR)
  • Low cost, compatible with current CMOS technology, and easy to integrate into existing manufacturing processes
  • Runs at room temperature and at very low voltage
  • Can be combined with existing technologies to offer flexibility

IP Status:

Tunneling Diode: Use and Manufacturing – US Pending
Using Backward Tunneling Diode as a Sensor – US Pending

Room-Temperature NDR Polymer Diodes for Flexible, Low-Power Electronics

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Summary:

Devices that exhibit a phenomenon known as negative differential resistance (NDR) have tremendous potential to deliver the kind of low-power circuitry needed in a variety of electronics applications. To understand NDR, it is instructive to recall Ohm’s Law, V=IR. For a fixed resistance (R), as voltage (V) increases, current (I) increases in a linear fashion. In NDR, there is a voltage range where increasing voltage actually results in a decreasing current. This behavior has many beneficial design properties, one of which is the design of low power memory and logic or even energy scavenging from the environment, eliminating the need for a self-contained battery.

Until now, successful demonstrations of NDR have been limited to rigid, inflexible semiconductor-based devices that are unsuitable for certain applications. Researchers at The Ohio State University have developed a polymer-based device that exhibits NDR and has the flexibility needed for advanced applications such as smartcards and wearable electronics. These devices enjoy very fast operation, which leads to high performance while consuming very little power. Furthermore, these devices can be manufactured in a very cost-effective manner using simple printing techniques.

Potential Applications:

  • Smartcards
  • Energy Scavenging
  • Development of advanced logic and memory circuits on flexible substrates

Advantages:

  • Large and reproducible NDR, at room temperature, in a flexible polymer device!
  • Low cost and simple solution processing
  • Fast operation at low power

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

Low-Cost, Fast, and Accurate System to Test Wire Pattern Continuity

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Summary:

Dr. Eric Walton of the ElectroScience Laboratory at the Ohio State University has developed a system for testing a conductive pattern that is fast, inexpensive, and accurate. Conductive patterns are found in a wide range of everyday products, from electronics to automobiles. One common application of a conductive pattern is the defroster/defogger on the rear window of an automobile. As the conductive wire patterns in these windows become more complex, methods of testing the continuity and quality of these patterns becomes more difficult and expensive. It is important that the testing system be robust enough to easily handle complex changes in pattern design, accurate enough to meet engineering standards, and inexpensive enough to be cost-effective to the manufacturer. This invention meets and exceeds all of these needs. This invention is just as useful in other applications such as the testing of printed circuit boards, the testing of conductive patterned surfaces used in electroforming, or the testing of any material in which conductive patterns are used for heating.

Potential Applications:

  • Invaluable tool for automotive glass manufacturers who aim to increase efficiency and reduce costs
  • Provides a fast and easy way to test the quality of printed circuit boards
  • A fantastic testing tool for the emerging field of printed electronics using conductive inks, which will find applications in e-readers, RFID tags, and other novel, groundbreaking electronic technologies

Advantages:

  • Reliable as the system is never in direct contact with the material to be tested
  • Inexpensive and easy to modify and/or replace components
  • Extremely accurate
  • Speed limited only by computing power and production capabilities
  • Easily integrated into an automated production line