Superconducting-cavity stabilized oscillators with improved frequency stability

X-band microwave oscillators stabilized with superconducting niobium cavities with loaded Q's of about 10¹⁰achieved short-term frequency stabilities as low as σy=6 × 10^-16, and typical long-term fractional frequency drifts of ± 2 × 10^-13per day.     

Measurement of electron attachment processes in a high-temperature plasma

An experimental technique has been developed for measuring rate constants of electron attaching reactions as well as ion-molecule reactions in plasma at 2000-3000°K. Reaction product ions are mass analyzed and rate constants are obtained from plots of the collected ion current. The rate constant for O^-formation from N2O varies from about 3 to 9×10^-9cm³/s over the temperature range of 2400-3000°K while the rate constant for F^-formation from SF6varies from 2.8 to 4×10^-10cm³/s for temperatures from 2775 to 3000°K. A brief survey of experimental techniques for measuring electron attachment rate constants at lower temperatures is also given, together with a comparison of these rate constants and present high-temperature values.     

Electronic properties of the silicon-thermally grown tantalum oxide interface

MOS capacitance measurements showed that the Si-Ta2O5interface prepared by thermal oxidation at ∼530°C of vacuum deposited Ta film followed by a heat treatment at 350°C in N2-H2is characterized by a negative "oxide" charge (6 × 10¹¹e/cm^-2at flat-band) and by an interface state density of ∼ 1 × 10¹²cm^-2(eV)^-1. The room temperature instability is small. The breakdown strength is >8 × 10⁶V/cm.     

Aging characteristics of AC plasma display panels

The initial accelerated aging ("burn-in") and the subsequent alternate-line-aging (ALA) characteristics of the operating voltages of ac plasma display panels were studied for MgO films deposited on dielectric glass substrates at 25°-350°C in a residual gas pressure of 10^-6-10^-7torr. To study the effects of the presence of oxygen during film deposition, the films were also deposited in 10^-4-10^-5torr of oxygen. Films deposited at 350°C showed significantly better aging characteristics than those deposited in 25°C. This observed dependence of the aging characteristics on the various parameters of the panel-fabrication process is explained in terms of a postulated effect of oxygen on the surface properties of MgO films and the changes in the surface properties of the MgO films (caused by changes in the surface stoichiometry) produced by ion bombardment during the discharge.     

Rejection characteristics in a video-signal processor using CCD comb filters

This paper describes charge-coupled device (CCD) combfilter rejection characteristics in the video bandwidth. Notch-frequency shifts and rejection-ratio decreases are caused by the incomplete charge transfer in the CCD channel and also by timing error in the charge sampling, which shorten the effective delay time from the ideal 1Hperiod. In the 1H comb filters, 30-dB rejections are achieved within the 4.5-MHz bandwidth for less than 2 × 10^-5per transfer inefficiency. The timing error in the input section can be compensated for by adjusting the input-gate biasing voltage. The analyses are extended to the 2Hcomb filter constructed with three identical CCD's. The 1.2 × 10^-4inefficiency, which is six times as large compared with that in the 1Hfilter, is allowable to maintain the 30-dB ratio. The rejection is shown to be constant when the product of the inefficiencies in the series-connected CCD's is constant. The experimentally obtained results suggest the analyses are reasonable.     

Hybrid IRCCD imaging array

A hybrid IRCCD for high background application has been successfully fabricated. The device consists of fifty Hg0.7Cd0.3Te detector diodes of 50-µm × 50-µm sensitive areas and a silicon CCD maltiplexer with input circuits on 40-µm centers having bucket background subtraction and blooming protection circuits. The noise-equivalent power (NEP) of the IRCCD is 5 × 10^-14W-Hz^-1/2at background photon flux level of 4 × 10¹⁵photons . cm^-2s^-1, integration time of 2 × 10^-5s, and clock frequency of 3 × 10⁶Hz. The noise source of the detector diodes limits the IRCCD performance. The IRCCD is also evaluated with the real-time raster-scanned thermal images displayed on a CRT monitor. Two-dimensional images are generated by using a scanning mirror. A fixed-pattern noise is reduced by comparison of an object video to the reference video stored in a memory. A noise-equivalent temperature difference of the system is 0.6°C at a frame rate of 30 Hz. Instantaneous field of view is 1 mrad × 1 mrad and the field of view of the system is 12° × 5.7°.     

The SIS tunnel emitter: A theory for emitters with thin interface layers

Silicon n-p-n transistors are made with emitters consisting of a polycrystalline and monocrystalline region with a thin (20-60-Å) "insulating" interfacial layer in between (SIS structure). These transistors show a remarkable increase in emitter efficiency with emitter Gummel numbers up to 7 × 10¹⁴s.cm^-4, and a low positive or even negative temperature coefficient of the current gain. A model is proposed to explain the mechanism in terms of tunneling through the interfacial layer. The electrical characteristics are measured in the temperature range 290-415 K. From the measurements it is deduced that the tunnel probability for holes (Ph) is 10^-2to 10^-3and that for electrons (Pe) is >10^-5. There also exists a band bending of 30-90 mV at the interfaces with the interfacial layer.     

GaInAs n-channel inversion-mode MISFET's with improved long- and short-term stability

CVD SiO2has been used as gate insulator for GaInAs n-channel inversion-mode MISFET's. By applying a rapid thermal annealing cycle with a maximum temperature of 700°C, the number of fast interface states could be strongly reduced, thus leading to stable device performance in the time range between 10^-6and 10 s. The drain current drift for longer times, however, is not affected by the annealing step. A reduction of the dielectric deposition temperature down to 250°C, however, results in improved long-term stability with a drain current decrease of only 5 percent after 10⁴s of operation at room temperature.     

Al—Ge ohmic contacts to n-type GaAs

Ohmic contacts have been fabricated to n-type GaAs with an alloy of AL-Ge which has an eutectic temperature of 424°C with 53- weight percent Germanium. The lowest contact resistance of 1.4 × 10^-6Ω.cm²was measured with a transfer length transmission line structure. The application to GaAs integrated-circuit design is demonstrated.     

Fast determination of the effective channel length and the gate Oxide thickness in polycrystalline Silicon MOSFET's

MOSFET's with variable channel lengths have been fabricated in both mono- and fine-grained polycrystalline silicon. We present a new method based upon a simple CV technique, to measure the effective channel length and gate oxide thickness. The channel-length reduction of the poly-Si MOSFET's was about 7.8 µm from which an effective lateral diffusion coefficient at 1000°C of phosphorus of 5 × 10^-13cm²/s was calculated. The electron mobility was in the range of 10-20 cm²/V.s and the threshold voltage was about 17 V. The MOSFET's in mono-Si have been used as a reference. The results of measurements on these devices are in agreement with literature.     

High-temperature stability of optical transmission properties attained by liquid-crystal polymer jacket

Liquid crystal polyester (LCP) tight jackets, developed as secondary coatings on optical fibers, exhibit Young's moduli of 10-20 GPa and linear expansion coefficients on the order of 10^-6/°C. Because of their low linear expansion coefficients, and because they exhibit no thermal shrinkage, the LCP jackets cause a slight change in fiber strain on the order of 10^-4percent/°C, or a change in the thermal coefficients of the transit time delay as low as 14-29 ps/km°C in an 80 to -60°C temperature range for tight-jacketed optical fibers. Furthermore, the LCP tight-jacketed optical fibers exhibit no excess loss in this temperature range.     

Effect of Sintering Temperature on the Properties of Fused Silica Ceramics Prepared by Gelcasting

Fused silica ceramics were fabricated by gelcasting, by use of a low-toxicity N′N-dimethylacrylamide gel system, and had excellent properties compared with those obtained by use of the low-toxicity 2-hydroxyethyl methacrylate and toxic acrylamide systems. The effect of sintering temperature on the microstructure, mechanical and dielectric properties, and thermal shock resistance of the fused silica ceramics was investigated. The results showed that sintering temperature has a critical effect. Use of an appropriate sintering temperature will promote densification and improve the strength, thermal shock resistance, and dielectric properties of fused silica ceramics. However, excessively high sintering temperature will greatly facilitate crystallization of amorphous silica and result in more cristobalite in the sample, which will cause deterioration of these properties. Fused silica ceramics sintered at 1275°C have the maximum flexural strength, as high as 81.32 MPa, but, simultaneously, a high coefficient of linear expansion (2.56 × 10^?6/K at 800°C) and dramatically reduced residual flexural strength after thermal shock (600°C). Fused silica ceramics sintered at 1250°C have excellent properties, relatively high and similar flexural strength before (67.43 MPa) and after thermal shock (65.45 MPa), a dielectric constant of 3.34, and the lowest dielectric loss of 1.20 × 10^?3 (at 1 MHz).     

Surface acoustic wave delay lines with small temperature coefficient

Surface acoustic wave delay lines having a vanishing first-order temperature coefficient of delay time near room temperature have been constructed. The devices were operated near 60 MHz and had about 5 µs delay. The surface waves, generated and received using interdigital electrodes, were propagated along the twofold crystallographic axis of ST-cut quartz. The phase delay change as a function of temperature has a parabolic temperature dependence with a second-order coefficient of approximately 31.5 × 10^-9/° C².     

Electrooptic effect in CdTe at 23.35 and 27.95 microns

The unlamped electrooptic coefficient r41of high-purity CdTe has been measured at 23.35 and 27.95 micros in the far infrared. The values obtained for n0³r41are 9.4 × 10^-11m/V at 23.35 µ and 8.1 × 10^-11m/V at 27.95 µ. Using previously reported values for n0, the electrooptic coefficients are found to be 5.5 × 10^-12m/V at 23.35 µ and 5.0 × 10^-12m/V at 27.95 µ. These measurements extend the region of observed electrooptic effect from 16 µ, previously obtained using GaAs, to 28 µ using CdTe.     

Experiments on high-perveance electron guns with a subfocusing electrode

High-perveance electron guns with a subfocusing electrode were designed analytically, produced, and tested. The experiments are carried out to evaluate the design method. Perveance of guns are 1.7 to 1.3 × 10^-6A/V^3/2, convergence angles being 30°. The results confirmed that it was possible to design electron guns of perveance up to 3.0 × 10^-6A/V^3/2.     

A method of determining impurity diffusion coefficients and surface concentrations of drift transistors

In order to control the electrical parameters of drift transistors, it was found necessary to control the impurity concentration gradient in the base. An extension of the space charge widening theory provides a method of calculating this gradient, the surface concentration, and the diffusion coefficient. By this method, the diffusion coefficient of arsenic into germanium at 725°C was found to be 3.1 × 10^-12cm²/second and the initial surface concentration was of the order of 10²⁰atoms/cm³. Universal graphs for design calculations and rapid reference are presented.     

A temperature-stable bandpass filter using dielectric resonators

A microstrip bandpass filter has been built with dielectric resonators made of a temperature-compensated material. Its unloaded Q at X band is calculated to be greater than 1200, a four-fold improvement upon conventional printed-on devices. With additional temperature compensation, a temperature coefficient less than 5 ppm/°C is shown to be feasible.     

Source—Drain contact resistance in CMOS with self-aligned TiSi2

The contact resistance between TiSi2and n⁺-p⁺source-drain in CMOS is studied for a variety of junction profiles and silicide thicknesses. It is shown that the measured contact resistance is consistent with the transmission-line model for electrically long contacts. The contact contribution to the total device series resistance can be significant if excessive silicon is consumed during silicide formation. Contact resistivities of 3 × 10^-7and 1 × 10^-6Ω . cm²can be obtained for 0.15-0.20-µm-deep arsenic and boron junctions, respectively, if the interface doping concentration is kept at 1 × 10²⁰/cm³. Furthermore, low-temperature measurements show that the contact resistivity is nearly constant from 300 to 77 K, as would be expected from a tunneling-dominated current transport at the TiSi2-n⁺and TiSi2-P⁺interfaces.     

Detailed performance characteristics of hybrid InP-InGaAsP APD's

Detailed performance characteristics of hybrid InP-InGaAsP APD's having negligible dark current (ID< 6 nA at M = 30) are reported. The excess noise factor F is found to be given by F/M ≈ const ≈ 0.42 ± 0.10 for gains in the range 5 ≤ M ≤ 35. The breakdown voltage increases with temperature according to ΔV_{BD}/V_{BD}/ΔT = 1.0 × 10^-3/°C. The dark current near breakdown doubles every 15°C. Sub-nanosecond rise times are observed, however, fall times are extended to ∼3 nsec by a diffusion tail that will be difficult to completely eliminate.     

Noise in short n+-n--n+GaAs diodes

Noise measurements in a short, near-ballistic, n⁺-n^--n⁺GaAs diode are reported. The device had a linear characteristic below 100 mA. It showed1/fnoise at low frequencies and a white noise close to the thermal noise of the device conductancegat high frequencies. The1/fnoise is most likely mobility fluctuation noise; we evaluated Hooge's parameter α and found a value of 1.95 × 10^-6at room temperature and 0.959 × 10^-6at liquid nitrogen temperature. We also observed a1/fnoise spectrum turning over into1/f^0.5spectrum at 77 K.