Tag Archives: detector

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

Carbon Monoxide (CO) Detector Operating at Room Temperature

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Summary:

Existing CO sensors are usually of either the electrochemical or optical variety. Inexpensive optical sensors, usually battery powered, are limited in their precision and lack displays to determine exact levels of CO concentration. Electrochemical devices offer higher precision and offer a display for CO concentration, but must operate at elevated temperatures and thus must be plugged in to a wall outlet. Researchers at The Ohio State University have developed an electrochemical CO sensor that operates and senses CO at room temperature, thus eliminating the need for a heating device. Therefore, energy demands are far lower when plugged in to a wall outlet, and a battery-powered electrochemical CO sensor can be achieved. This sensor can monitor CO in the ppm range and can be readily fabricated by screen printing techniques with deposition on polymer substrates. Sensors are miniaturizable.

Potential Applications:

  • Home, office, and industrial CO monitoring for occupant safety and fire detection
  • CO sensors can be incorporated into mobile devices, such as cell phones

Advantages:

  • Increased safety and sensor longevity as no heating device is needed
  • For the first time, battery-powered electrochemical CO sensors are possible
  • A portable, battery-powered CO sensor with a display becomes possible
  • Great reduction in energy consumption
  • Low-cost and easy to manufacture

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

Undetectable, Unjammable, and Interference-Free Ultra Wideband Radar System

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Summary:

Researchers at the Ohio State University have developed a virtually undetectable ultra wide band radar system that transmits pseudo random noise. On receive, the radar system cross-correlates a copy (possibly modified) of the original waveform with the receive signals. If a target reflects the signal (with modifications) then the radar will detect the reflection, the time delay, and Doppler. Thus the radar can tell the distance to a reflecting object and its relative speed. This is done using a waveform that will not interfere with other users of the spectrum. The noise waveform is extremely hard to detect. Researchers have further developed a system of storing the waveforms and performing the cross correlation at a particular time delay using a single memory device and no delay devices. This lends to the creation of a small, low cost, low power, stealthy radar that cannot be easily detected by conventional radar detection equipment and can be used for very short range applications. The radar can also be used to identify radar targets by using a pair of waveforms matched to the target radar impulse response. Thus the radar can also be used to detect only specific types of targets, as maybe required by the application.

Potential Applications:

  • Speed radar gun manufacturers seeking an undetectable radar gun
  • Simple moving vehicle/person/object with identification potential (automotive lane change warning)
  • Highway management to evaluate strength of material, or helicopter air to air warning systems
  • Low cost ground penetration radar for pipes, land mine detection, or probing human bodies
  • Low cost building penetration radar (security systems at casinos and airports)
  • Cross section instrumentation radar with inverse synthetic aperture imaging radar ability
  • Moving Radar, synthetic aperture radar systems

Advantages:

  • Robust with reference to interference or jamming – thus undetectable and hard to intercept
  • Unlikely to interfere with other noise radar systems or other radar systems in the same band
  • Low cost, small, light weight, and can be used for very short-range applications
  • Can be trained to be target specific (with the ability to specify multiple targets)
  • Would require no license to operate in civilian bands, and is fully coherent in amplitude and phase