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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

InGaAs/InAlAs hot-electron transistor

Using InGaAs for the base and InAlAs for the emitter and collector barriers, the first hot-electron transistor in this material system is fabricated. It is shown that 1.6 percent of the injected hot electrons can be transported ballistically through a 0.3 micron thick In(0.53)Ga(0.47)As plus 800-A-thick InAlAs barrier layer at 77 K giving rise to an average mean free path of 920 A. An energy spread of 130 MeV was observed for the ballistic electrons injected at about 700 MeV above the thermal equilibrium conditions. The value of collector barrier heights measured are in reasonable agreement with those deduced independently from thermionic emission studies in InGaAs gate, InAlAs/InGaAs capacitor structures.

Reddy, U. K.↗
NASA NTRS1988

Contact regrowth technique for low-resistance nonalloyed contacts to the hot-electron transistor

A novel contact regrowth technique for the formation of extremely low nonalloyed ohmic contacts is reported. The successful demonstration of this technique is reported on an InGaAs/InAlAs hot-electron transistor device. For the investigated InGaAs-based structure, the regrown contacting scheme reported includes an In(0.53)Ga(0.47)As layer, an InAs/GaAs strained-layer superlattice, and an InAs cap, all heavily doped n type with Si. A very low specific contact resistance of 1.8 x 10 to the -7th ohm sq cm to the base layer is obtained. The higher current densities achieved in the transistor characteristics are in close agreement with calculations, and a contact model is presented explaining the poor results of conventional nonalloyed contacts.

Peng, C. K.↗
NASA NTRS1995

Long-Wavelength-Infrared Hot-Electron Transistor

Dark current reduced by energy-discriminating quantum filter. Very long-wavelength-infrared hot-electron transistor developed. Device detects photons at wavelengths around 16 micrometers. Comprises photodector integrated with energy-discriminating quantum filter in multiple-quantum-well structure. Made of variously doped and undoped layers of GaAs (quantum wells) and Al(x)Ga(1-x)As (barriers between wells). In transistor, bound-to-continuum GaAs/Al(x)Ga(1-x)As multiple-quantum-well infrared photodectors (QWIP) serves as photosensitive emitter. Wide quantum well serves as base, and there is thick barrier between base and collector. Combination of barrier and base quantum well acts as energy-discriminating filter: electrons with higher energies pass through filter to collector, those with lower energies blocked and diverted from output-current path through base contact.

Gunapala, Sarath D.↗
NASA NTRS1990

Impact ionization in the base of a hot-electron AlSb/InAs bipolar transistor

The operation of a new AlSb/InAs heterojunction bipolar transistor is studied. The electrons are injected into a p-InAs base across the AlSb/InAs heterojunction. The conduction-band discontinuity at this heterojunction is sufficiently large so that energy of the electrons injected into InAs exceeds the threshold for generating electron-hole pairs by impact ionization. The observed incremental common base current at zero collector-base bias decreases and becomes negative as the emitter current is increased, thus providing direct evidence for impact ionization entirely by band-edge discontinuities.

Vengurlekar, Arvind S.↗
NASA NTRS1995

Time-Resolved IR-Absorption Spectroscopy of Hot-Electron Dynamics in Satellite and Upper Conduction Bands in GaP

The relaxation dynamics of hot electrons in the X6 and X7 satellite and upper conduction bands in GaP was directly measured by femtosecond UV-pump-IR-probe absorption spectroscopy. From a fit to the induced IR-absorption spectra the dominant scattering mechanism giving rise to the absorption at early delay times was determined to be intervalley scattering of electrons out of the X7 upper conduction-band valley. For long delay times the dominant scattering mechanism is electron-hole scattering. Electron transport dynamics of the upper conduction band of GaP has been time resolved.

Cavicchia, M. A.↗
NASA NTRS1973

Microwave properties of n-type InSb in a magnetic field between 4 and 300 K.

A two-band conduction model is used to determine the properties of shallow-type impurity semiconductors in the presence of microwave and dc magnetic fields as a function of temperature. Measurements using cavity perturbation techniques are employed to determine the properties of n-type InSb and theoretical and experimental results between 4 and 300 K are compared. The hot-electron effect was found to be insignificant between 77 and 300 K, and the scattering mechanisms are dominated by acoustic and polar modes over the same temperature range.-

Eldumiati, I. I.↗
NASA NTRS1973

Observation of the J = 2 to J = 1 transition of interstellar CO at 1.3 millimeters

The NRAO 36-foot antenna at Kitt Peak with a novel type of millimeter-wave superheterodyne receiver was used in observations of 1.3-mm line interstellar radiation due to J ? 2-1 transitions of C(12)0(16) and C(13)0(16). The liquid-helium-cooled hot-electron bolometer mixer of the superheterodyne receiver was used as the detecting element. The Orion Nebula CO system was found to be thermalized, showing a peak excitation temperature of about 76 K.

Phillips, T. G.↗
NASA NTRS1985

Submillimeter wave absorption of n-type InSb at low temperatures

The absorption coefficient of two high-purity n-InSb samples is measured in the 10-40 per cm range using Fourier transform spectroscopy. The absorption coefficient spectrum is presented for both samples at 4.2 K. It is also shown for the lower resistance sample cooled to 2.2 K and heated by dc bias to elevated electron gas temperatures of 7.5 and 17.9 K. ac Drude theory gives rather poor agreement with experiment at 2.2 and 4.2 K but does much better when the sample electron gas is heated. In contrast, a simple quantum mechanical theory of absorption based on inverse Bremsstrahlung yields promising agreement at the lower temperatures although its applicability is questionable. The non-Drudian absorption is shown to have a favorable effect on the performance of InSb hot-electron bolometers.

Brown, E. R.↗
NASA NTRS1985

Absolute response and noise equivalent power of cyclotron resonance-assisted InSb detectors at submillimeter wavelengths

Spectra are presented of the responsivity and noise equivalent power (NEP) of liquid-helium-cooled InSb detectors as a function of magnetic field in the range 20-110 per cm. The measurements are all made using a Fourier transform spectrometer with thermal sources. The results show a discernable peak in the detector response at the conduction electron cyclotron resonance (CCR) frequency for magnetic fields as low as 3 kG. The magnitude of responsivity at the resonance peaks is roughly constant with magnetic field and is comparable to the low-frequency hot-electron bolometer response. The NEP at the peaks is found to be comparable to the best long wavelength results previously reported. For example, NEP = 4.5 x 10 to the 13th W/(square root of Hz) at 4.2 K, 6 kG, and 40 per cm was measured. The InSb CCR will provide a much improved detector for laboratory spectroscopy, as compared with hot electron bolometers, in the 20-100 per cm range.

Brown, E. R.↗
NASA NTRS1985

Reliability analysis

The objective was to search for and demonstrate approaches and concepts for fast wafer probe tests of mechanisms affecting the reliability of MOS technology and, based on these, develop and optimize test chips and test procedures. Progress is reported on four important wafer-level reliability problems: gate-oxide radiation hardness; hot-electron effects; time-dependence dielectric breakdown; and electromigration.

Source record↗
NASA NTRS1987

Numerical study of the spectrum of broadband electrostatic noise in the magnetotail

A numerical study of the spectrum of broadband electrostatic noise (BEN) generated by ion beams in the plasma sheet boundary layer (PSBL) is presented, in which two cases are analyzed. The first case is concerned with a single hot-electron species. In the second case, a second population of cold electrons (arising from diffusion from the lobe into the PSBL) is introduced. The presence of the second electron component in the dispersion relation for generating BEN was found to significantly increase the upper frequency range of the unstable spectrum, enhancing the associated growth rates. It is shown that ion beam instabilities can explain most major features of the observed BEN spectrum. The results explain the gradual rise in the upper frequency range of BEN as a spacecraft approaches the plasma sheet from the lobe, and the sudden jump in that frequency up to near the plasma frequency upon crossing the PSBL.

Grabbe, Crockett L.↗