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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS2002

Cryogenically Cooled Field Effect Transistors for Low-Noise Systems

Recent tends in the design, fabrication and use of High-Electron-Mobility-Transistors (HEMT) in low noise amplifiers are reviewed. Systems employing these devices have achieved the lowest system noise for wavelengths greater than three millimeters with relatively modest cryogenic cooling requirements in a variety of ground and space based applications. System requirements which arise in employing such devices in imaging applications are contrasted with other leading coherent detector candidates at microwave wavelengths. Fundamental and practical limitations which arise in the context of microwave application of field effect devices at cryogenic temperatures will be discussed from a component and systems point of view.

Wollack, Edward J.↗
NASA NTRS1991

Plasma-deposited germanium nitride gate insulators for indium phosphide metal-insulator-semiconductor field-effect transistors

Plasma-deposited germanium nitride was investigated for the first time as a possible gate insulator for InP compound semiconductor metal-insulator-semiconductor FET (MISFET) technology. The germanium nitride films were successfully deposited in a capacitively coupled parallel plate reactor at 13.56 MHz operation using GeH4/N2/NH3 and GeH4/N2 mixtures as reactant gases. The former process produced better quality films with enhanced uniformity, increased deposition rates, and increased resistivity. The breakdown field strength of the films was greater than 10 to the 6th V/cm. Auger electron spectroscopy did not indicate significant chemical composition differences between the two processes. For MISFETs with 2-micron channel lengths fabricated on InP, the device transconductance and threshold voltage for the GeH4/N2/NH3 process were 17 mS/mm and -3.6 V, respectively. The drain-source breakdown voltages were greater than 10 V.

Johnson, Gregory A.↗
NASA NTRS1969

Field Effect Transistor /FET/ circuit for variable gin amplifiers

Amplifier circuit using two FETs combines improved input and output impedances with relatively large signal handling capability and an immunity from adverse effects of automatic gain control. Circuit has sources and drains in parallel plus a resistive divider for signal and bias to either of the gate terminals.

Spaid, G. H.↗
NASA NTRS1972

Insulated-gate field-effect transistor strain sensor

Strain sensors that can be switched on and off were fabricated from p-channel IGFET on thin filament n-type silicon crystals with silicon dioxide layer sputtered over transistor for passivation. Applications include integration with microelectronic circuits for multiplexing.

Gross, C.↗
NASA NTRS1973

Gyrator circuit using field effect transistors

Gyrator circuit is especially useful in integrated circuits for such purposes as simulating inductors with capacitors. Circuit is adaptable to semifloating and full floating configurations. It has excellent response, low power consumption, and high energy storage capacity.

Hochmair, E. S.↗
NASA NTRS1980

JANTX2N4856 field-effect transistor

Report evaluates effects of power and temperature overstress on Teledyne and Texas Instruments devices. Temperature stress caused most failures for both manufacturers' lots. Failure modes are analyzed.

Source record↗
NASA NTRS1982

Design, production, and testing of field effect transistors

Cryogenic MOSFETS (CRYOFETS), specifically designed for low temperature preamplifier application with infrared extrinsic detectors were produced and comparatively tested with p-channel MOSFETs under matched conditions. The CRYOFETs exhibit lower voltage thresholds, high source-follower gains at lower bias voltage, and lower dc offset source voltage. The noise of the CRYOFET is found to be 2 to 4 times greater than the MOSFET with a correspondingly lower figure of merit (which is established for source-follower amplifiers). The device power dissipation at a gain of 0.98 is some two orders of magnitude lower than for the MOSFET. Further, CRYOFETs are free of low temperature I vs V character hysteresis and balky conduction turn-on effects and operate effectively in the 2.4 to 20 K range. These devices have promise for use on long term duration sensor missions and for on-focal-plane signal processing at low temperatures.

Sclar, N.↗
NASA NTRS1983

Brief characterization of germanium junction field effect transistors (FETs) at 77, 4, and 1.8 K

In the case of modern infrared focal planes, one of the major problems is related to the noise contribution of the cooled, impedance-matching device used as the preamplifier stage in the detector electronics system. An ideal preamp device should have the low-noise advantages of a buried-channel device and operate isothermally with the low-temperature detector array. The Ge JFET might provide this ideal device. A testing program with Ge JFETs is discussed. It is concluded that germanium JFETs offer an attractive alternative for cryogenic preamplifier designs. They operate well with high transconductance and low noise at LHe temperatures. It is believed that these devices point the way for the development of large, integrated-array, long wavelength, infrared focal planes which incorporate germanium detectors, germanium load resistors, and germanium preamplifiers within the same monolithic structure.

Arentz, R. F.↗
NASA NTRS1986

Determination of carrier saturation velocity in high-performance In(y)Ga(1-y)As/Al(x)Ga(1-x)As modulation-doped field-effect transistors (with y between 0 and 0.2)

The relation between the intrinsic transconductance per unit gate width and the carrier saturation velocity, v(sat), is used to determine v(sat) for several high-performance pseudomorphic MODFET's with different InAs mole fractions (y). Measurements of In(y)Ga(1-y)As/AlGaAs MODFET's grown by MBE were found to give accurate v(sat) values at 77 K. Devices with y between 0 and 0.20 were shown to have higher v(sat) than conventional GaAs/AlGaAs MODFET's. An optimum y value for peak v(sat), which may optimize overall device performance, is expected.

Henderson, T. S.↗
NASA NTRS1986

Characterization of InGaAs/AlGaAs pseudomorphic modulation-doped field-effect transistors

High-performance pseudomorphic In(y)Ga(1-y)As/Al0.15-Ga0.85As y = 0.05-0.2 MODFET's grown by MBE have been characterized at dc (300 and 77 K) and RF frequencies. Transconductances as high 310 and 380 mS/mm and drain currents as high as 290 and 310 mA/mm were obtained at 300 and 77 K, respectively, for 1-micron gate lengths and 3-micron source-drain spacing devices. Lack of persistent trapping effects, I-V collapse, and threshold voltage shifts observed with these devices are attributed to the use of low mole fraction Al(x)Ga(1-x)As while still maintaining two-dimensional electron gas concentrations of about 1.3 x to the 12th per sq cm. Detailed microwave S-parameter measurements indicate a current gain cut-off frequency of 24.5 GHz when y = 0.20, which is as much as 100 percent better than similar GaAs/AlGaAs MODFET structures, and a maximum frequency of oscillation of 40 GHz.

Ketterson, Andrew A.↗