Tag Archives: device

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

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

Direct, Low Frequency Capacitance Measurement for Scanning Capacitance Microscopy

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Summary:

Scanning capacitance microscopy (SCM) circuits, used for such applications as semiconductor characterization (including dopant profiling, device characterization, and surface defect characterization), are typically not adapted for calibrated, low frequency measurements of absolute capacitance. In fact, these implementations of SCM generally do not measure capacitance directly. Rather, they measure the change in capacitance versus the change in voltage (dC/dV) by varying the probe-sample voltage V at frequencies greater than 10 kHz. This is due to a voltage dependant capacitance resulting from a voltage-dependant space change layer in the semiconductor substrate. The Ohio State University has developed a system and method for performing scanning capacitance microscopy using an atomic force microscope (AFM) that measures direct capacitance at a frequency less then 10 kHz. The system exhibits high sensitivity with very low noise. Recent advancements to this technology have resulted in even higher sensitivity by enabling direct measurements of absolute capacitance at higher frequencies. The design of the circuit has also been simplified, enabling the use of off-the-shelf components such as function generators. This straightforward design will shorten the investment of time and money needed to commercialize this powerful system.

Potential Applications:

This system is an ideal tool for semiconductor characterization. It is also useful for measuring a wide variety of dielectric films such as SiO2 grown on Si, or for dielectric films on other semiconductor substrates such as Si3N4, Al2O3, TiO2, and ZrO2. It may also be used to measure thin lubricant films such as perfluoropolyethers, a widely used class of compounds for MEMS and hard disk drive lubrication. Other suitable types of samples include self-assembled monolayers.

Advantages:

  • Enables direct capacitance measurements at low frequencies
  • Low noise
  • High sensitivity
  • Straightforward yet powerful design
  • Can also determine stray capacitance

Novel Organic Light Emitting Diode (OLED) Technologies for Lighting and Display Applications

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Summary:

Researchers at The Ohio State University have developed a comprehensive portfolio of Organic Light Emitting Diode (OLED) technologies that include novel materials and device architectures as platforms for functional devices and for device manufacturing. These developments improve material stability over time while improving their performance such that the required voltage can be reduced and improved electroluminescence can be obtained with reduced power consumption. The bilayer device structure improves device quantum efficiency and brightness due to charge confinement and exciplex emission at the emitting polymer interface. Beyond advancements in the materials themselves, novel device architectures have been developed which are independent of the materials used. These advancements may be of significant value in simplifying manufacturing, thereby accelerating the displacement of LCD and plasma display technologies as well as the displacement of traditional incandescent and fluorescent lighting sources. The associated patent portfolio consists of 8 patent families with a total of 11 issued U.S. patents and 39 associated national stage filings (spanning all US cases). A listing of all issued U.S. patents can be found below.

Potential Applications:

  • Conformal, designable, and color-variable interior and exterior lighting for residential and commercial environments
  • Power and weight sensitive lighting and display applications (e.g. aircraft interior lighting, portable display backlighting)
  • Portable lighting devices such as flashlights
  • Light, ultra-thin, flexible displays with rich colors viewable from very wide angles
  • Body-wearable lighting and display applications
  • Nearly endless list of potential applications

Advantages:

  • More energy efficient lighting source compared to incandescent and fluorescent approaches
  • Color quality matches or surpasses conventional approaches in lighting and display applications
  • Estimated useful life is approximately 17-25 times longer than incandescent lighting and nearly twice as long as linear flourescent lighting (which is commonly used in modern LCD displays)
  • Polymeric material is conformal to a wide range of surface topologies and allows for ultra-thin, flexible displays
  • Low cost, materials-independent architectures have the potential to lower manufacturing costs
  • Adjustable color spectrum