Semiconductors & ICs

HEMT Amplifiers and Equipment for Their On-Wafer Testing

Power levels in CPW circuits can be measured without packaging.

Power amplifiers comprising InP-based high-electron-mobility transistors (HEMTs) in coplanar-waveguide (CPW) circuits designed for operation at frequencies of hundreds of gigahertz, and a test set for on-wafer measurement of their power levels have been developed. These amplifiers utilize an advanced 35-nm HEMT monolithic microwave integrated-circuit (MMIC) technology and have potential utility as local- oscillator drivers and power sources in future submillimeter-wavelength heterodyne receivers and imaging systems. The test set can reduce development time by enabling rapid output power characterization, not only of these and similar amplifiers, but also of other coplanar-waveguide power circuits, without the necessity of packaging the circuits.

Posted in: Briefs, Semiconductors & ICs, Amplifiers, Integrated circuits, Amplifiers, Integrated circuits, Test procedures
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On-Wafer Measurement of a Silicon-Based CMOS VCO at 324 GHz

Compact, low-power, electronically tunable submillimeter-wave local oscillators are now feasible.

The world’s first silicon- based complementary metal oxide/semi- conductor (CMOS) integrated-circuit voltage-controlled oscillator (VCO) operating in a frequency range around 324 GHz has been built and tested. Concomitantly, equipment for measuring the performance of this oscillator has been built and tested. These accomplishments are intermediate steps in a continuing effort to develop low-power- consumption, low-phase-noise, electronically tunable signal generators as local oscillators for heterodyne receivers in submillimeter-wavelength (frequency > 300 GHz) scientific instruments and imaging systems. Submillimeter-wavelength imaging systems are of special interest for military and law-enforcement use because they could, potentially, be used to detect weapons hidden behind clothing and other opaque dielectric materials. In comparison with prior submillimeter-wavelength signal generators, CMOS VCOs offer significant potential advantages, including great reductions in power consumption, mass, size, and complexity. In addition, there is potential for on-chip integration of CMOS VCOs with other CMOS integrated circuitry, including phase-lock loops, analog-to-digital converters, and advanced microprocessors.

Posted in: Briefs, TSP, Semiconductors & ICs, Amplifiers, Imaging, Imaging and visualization, Integrated circuits, Semiconductor devices, Amplifiers, Imaging, Imaging and visualization, Integrated circuits, Semiconductor devices, Silicon alloys
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Lower-Dark-Current, Higher-Blue-Response CMOS Imagers

Semiconductor junctions are relocated away from Si/SiO2 interfaces.

Several improved designs for complementary metal oxide/semiconductor (CMOS) integrated- circuit image detectors have been developed, primarily to reduce dark currents (leakage currents) and secondarily to increase responses to blue light and increase signal- handling capacities, relative to those of prior CMOS imagers. The main conclusion that can be drawn from a study of the causes of dark currents in prior CMOS imagers is that dark currents could be reduced by relocating p/n junctions away from Si/SiO2 interfaces. In addition to reflecting this conclusion, the improved designs include several other features to counteract dark-current mechanisms and enhance performance.

Posted in: Briefs, Semiconductors & ICs, Imaging, Imaging and visualization, Integrated circuits, Semiconductor devices, Imaging, Imaging and visualization, Integrated circuits, Semiconductor devices, Performance upgrades
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Low-Temperature Supercapacitors

Electrolyte compositions are designed to extend the low-temperature operational limit.

An effort to extend the low-temperature operational limit of supercapacitors is currently underway. At present, commercially available non-aqueous supercapacitors are rated for a minimum operating temperature of –40 °C. A capability to operate at lower temperatures would be desirable for delivering power to systems that must operate in outer space or in the Polar Regions on Earth.

Posted in: Briefs, TSP, Semiconductors & ICs, Ultracapacitors and supercapacitors, Ultracapacitors and supercapacitors, Performance upgrades
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MEMS/ECD Method for Making Bi₂₋ₓSbₓTe₃ Thermoelectric Devices

Devices containing diverse materials in complex three-dimensional shapes can be fabricated.

A method of fabricating Bi2–xSbxTe3-based thermoelectric microdevices involves a combination of (1) techniques used previously in the fabrication of integrated circuits and of microelectromechanical systems (MEMS) and (2) a relatively inexpensive MEMS-oriented electrochemical- deposition (ECD) technique. The devices and the method of fabrication at an earlier stage of development were reported in “Sub milli meter-Sized Bi2–xSbxTe3 Thermoelectric Devices” (NPO-20472), NASA Tech Briefs, Vol. 24, No. 5 (May 2000), page 44. To recapitulate: A device of this type generally contains multiple pairs of n- and p-type Bi2–xSbxTe3 legs connected in series electrically and in parallel thermally. The Bi2–xSbxTe3 legs have typical dimensions of the order of tens of microns. Metal contact pads and other non-thermoelectric parts of the devices are fabricated by conventional integrated-circuit and MEMS fabrication techniques. The Bi2–xSbxTe3 thermoelectric legs are formed by electrodeposition, through holes in photoresist masks, onto the contact pads.

Posted in: Briefs, Semiconductors & ICs, Architecture, Integrated circuits, Microelectricmechanical device, Microelectromechanical devices, Architecture, Integrated circuits, Microelectricmechanical device, Microelectromechanical devices, Fabrication
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Compact, Single-Stage MMIC InP HEMT Amplifier

This amplifier exhibits gain of 5 dB at 340 GHz.

Figure 1 depicts a monolithic microwave integrated-circuit (MMIC) single-stage amplifier containing an InP-based high- electron-mobility transistor (HEMT) plus coplanar-waveguide (CPW) transmission lines for impedance matching and input and output coupling, all in a highly miniaturized layout as needed for high performance at operating frequencies of hundreds of gigahertz. This is one in a series of devices that are intermediate products of a continuing effort to develop advanced MMIC amplifiers for sub-millimeter-wavelength imaging systems, scientific instrumentation, heterodyne receivers, and other applications.

Posted in: Briefs, TSP, Semiconductors & ICs, Amplifiers, Architecture, Integrated circuits, Transistors, Waveguides, Amplifiers, Architecture, Integrated circuits, Transistors, Waveguides
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Radiation-Insensitive Inverse Majority Gates

These gates would be implemented as microscopic vacuum electronic devices.

To help satisfy a need for high-density logic circuits insensitive to radiation, it has been proposed to realize inverse majority gates as microscopic vacuum electronic devices. In comparison with solid-state electronic devices ordinarily used in logic circuits, vacuum electronic devices are inherently much less adversely affected by radiation and extreme temperatures.

Posted in: Briefs, TSP, Semiconductors & ICs, Integrated circuits, Integrated circuits, Radiation protection
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Performance of 1mm² Silicon Photomultipliers

A silicon photomultiplier (SPM) is a new type of semiconductor detector that has the potential to replace the photo- multiplier tube (PMT) detector in many applications. In common with a PMT detector, the output of an SPM is an easily detectable current pulse for each detected photon and can be used in both photon counting mode and as an analogue (photocurrent) detector. However, the SPM also has a distinct advantage over PMT detectors. The photon-induced current pulse from a PMT varies greatly from photon to photon, due to the statistics of the PMT multiplication process (excess noise). In contrast, the current pulse from an SPM is identical from photon to photon. This gives the SPM a distinct advantage in photon counting applications as it allows the associated electronics to be greatly simplified. Identical pulses also mean that the SPM can resolve the number of photons in weak optical pulses, so-called photon number resolution. This is critical in a number of applications including linear-optics quantum computing.

Posted in: Articles, Semiconductors & ICs, Detectors, Semiconductors, Test equipment and instrumentation
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Dual-Input AND Gate From Single-Channel Thin-Film FET

These transistors show potential as large-area, low-cost electronic circuitry on rigid and flexible substrates.

A regio-regular poly (3-hexylthiophene) (RRP3HT) thin-film transistor having a split-gate architecture has been fabricated on a doped silicon/silicon nitride substrate and characterized. RRP3HT is a semiconducting polymer that has a carrier mobility and on/off ratio when used in a field effect transistor (FET) configuration. This commercially available polymer is very soluble in common organic solvents and is easily processed to form uniform thin films. The most important polymer-based device fabricated and studied is the FET, since it forms the building block in logic circuits and switches for active matrix (light-emitting-diode) (LED) displays, smart cards, and radio frequency identification (RFID) cards.

Posted in: Briefs, TSP, Semiconductors & ICs, Architecture, Transistors, Architecture, Transistors, Product development, Fabrication, Polymers, Semiconductors
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Split-Block Waveguide Polarization Twist for 220 to 325 GHz

This device is superior to conventional twisted rectangular waveguides for submillimeter wavelengths.

Figure 1. A Channel Having Asymmetric Steps is cut into the lower block.An identical channel is cut into the upper block. Then with the help ofalignment pins, the blocks are assembled so that the two channels mergeinto one channel that makes a transition between two orthogonal orientationsof a WR-3 waveguide.A split-block waveguide circuit that rotates polarization by 90° has been designed with WR-3 input and output waveguides, which are rectangular waveguides used for a nominal frequency range of 220 to 325 GHz. Heretofore, twisted rectangular waveguides equipped with flanges at the input and output have been the standard means of rotating the polarizations of guided microwave signals. However, the fabrication and assembly of such components become difficult at high frequency due to decreasing wavelength, such that twisted rectangular waveguides become impractical at frequencies above a few hundred gigahertz. Conventional twisted rectangular waveguides are also not amenable to integration into highly miniaturized subassemblies of advanced millimeter- and submillimeter- wave detector arrays now undergoing development. In contrast, the present polarization-rotating waveguide can readily be incorporated into complex integrated waveguide circuits such as miniaturized detector arrays fabricated by either conventional end milling of metal blocks or by deep reactive ion etching of silicon blocks. Moreover, the present splitblock design can be scaled up in frequency to at least 5 THz.

Posted in: Briefs, TSP, Semiconductors & ICs, Waveguides, Waveguides
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