摘要:

A GaAsp‐n‐i‐ndiode which operates as a light‐activated light‐coupled switch is described. Thei‐region is compensated semi‐insulating GaAs and is obtained by diffusing Cu, Fe, or Cr into low‐dopedn‐GaAs. The electrical and optical properties of this diode have been studied as well as its switching behavior. The diode exhibits a current‐controlled negative resistance region with ratio of off‐ to on‐resistance as high as 106. Turn‐on voltages range from 10 to 200 V, and the turn‐on time can be made as short as 10 nsec with sufficient overvoltage. The current is limited in the high‐resistance mode by intrinsic or one‐carrier space‐charge‐limited conduction in theiregion. At higher currents the light emission at thep‐njunction causes photoconduction in theiregion which is enhanced by the trapping of holes at acceptor levels. In the low‐resistance mode all the traps (approximately 1016cm−3) are filled and remain that way because of the high efficiency of light emission from the junction at the high currents. A model is developed which semiquantitatively describes both the static and dynamic properties of the diode.

ISSN:0021-8979    

DOI:10.1063/1.1708939

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The relative intensities of the 4358, 3651, and 3131 Å radiation and the ratios of intensities of the 5461, 4358, 3651, 3131, 3125, and 2967 Å radiation were studied experimentally as a function of position in the negative glow of a Hg&sngbnd;H2dc abnormal glow discharge. These results are displayed in graphical form under conditions of varying H2pressure. Extrapolations of the relative density ratios of the 63D3,2,1and 73S1states were obtained from these intensity measurements. Quenching of the Hg 63P2,1,0states by H2in the negative glow region is discussed.

ISSN:0021-8979    

DOI:10.1063/1.1708940

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

It is demonstrated that instead of yielding unique values of &agr; and &bgr; for yttrium iron garnet (YIG) and lithium ferrite, the analytic method of calculating molecular field coefficients in ferrimagnets yields only one of many possible (&agr;, &bgr;) pairs from a linearly related set. The magnitudes of the internal magnetic fields, total magnetic moment, and the two sublattice magnetic moments, computed from any of the possible coefficients, remain relatively unchanged even though (&agr;, &bgr;) andnare extremely sensitive to the input parameters and number of experimental data points. It is shown how this manifold of (&agr;, &bgr;) pairs can exist, how the pairs can be linearly related, and how an analytic expression for this dependency can be derived, using low‐temperature data. A procedure for testing whether the coefficients for other ferrimagnets can be uniquely determined is discussed. ``Best'' values of (&agr;, &bgr;), obtained by minimizing a least‐squares percentage error, not only fall along a straight line but are in good agreement with those usually generated by the analytic method. The use of the ``linearity'' test in theX‐Ygraph as a criterion for judging the appropriateness of the selected value of the Curie point is shown to be invalid.

ISSN:0021-8979    

DOI:10.1063/1.1708941

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

An investigation of imperfections due to selective‐area planar double diffusions ofn‐ andp‐type impurities on epitaxial silicon has shown that elastic and inelastic lattice strain exists at the edges of oxide windows. This strain may act as nucleation sites for precipitating metallic impurities. High‐surface‐concentration emitter impurities (phosphorus) cause residual, inelastic strains at oxide edges, while base diffusions (boron) normally cause elastic lattice strains. X‐ray transmission topography reveals both elastic and inelastic strains. Surface reflection x‐ray topography is slightly more sensitive than x‐ray transmission topography for detecting defects due to shallow phosphorus diffusion. Chemical etching techniques delineate line defects which are unresolved by x‐ray techniques. The line defects are confined to the emitter area and extend in ⟨110⟩ and ⟨112⟩ directions. Differences in the results obtained by both x‐ray techniques are discussed in terms of defects observed by etching techniques.

ISSN:0021-8979    

DOI:10.1063/1.1708943

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The temperature dependence of the Hall constant, resistivity, and Hall mobility was measured for Ge films deposited on polished (111) CaF2substrates at substrate temperatures of 200°–700°C, deposition rates of 100–15 000 Å/min, and for film thicknesses between 800 and 170 000 Å. For formation conditions which improved film structures, electrical properties likewise improved. For single‐crystal films the Hall constant and Hall mobility increased as the defect density decreased with increasing deposition temperature and decreasing deposition rate. Similarly, for films thicker than 4000 Å, as the density of defects intersecting the surface decreased with increasing thickness, the Hall constant and mobility increased. Hole‐carrier concentrations of 1016–1018per cm3and room‐temperature Hall mobilities of 100–1100 cm2/V·sec were observed. The results indicate that defects are the source of acceptors and contribute significantly to scattering.

ISSN:0021-8979    

DOI:10.1063/1.1708944

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The crystallographic orientation of obliquely evaporated CdS films has been investigated by x‐ray and electron diffraction to provide the information required to control the fabrication of shear mode thin film ultrasonic transducers. Some degree of preferred orientation, with thecaxis normal to the film plane, was observed in the initial layers of all of the films examined. The degree of preference was primarily dependent upon the structure of the substrate. As the films increased in thickness, on all except highly (111)‐oriented gold substrate, an oblique orientation developed with thecaxis of the crystallites strongly inclined towards the incident vapor beam. On the highly (111)‐oriented gold‐film substrates, the CdS films remainedc‐axis preferred. The effects of substrate structure and of the rate and angle of the deposition have been examined. Ultrasonic transducer data are presented and compared with the crystallographic structure of the transducer films showing the expected correlation between thec‐axis orientation and the ultrasonic mode generated.

ISSN:0021-8979    

DOI:10.1063/1.1708945

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The velocity spread existing on a velocity‐modulated electron beam of finite diameter is investigated as a function of drive, drift length, and perveance using a digital computer program based on a disk electron model. At small signal levels the velocity modulation decreases cosinusoidally to zero with drift distance in accordance with one‐dimensional bunching theory. At higher signal levels, however, the velocity spread does not go to zero due to aberrations introduced by the finite diameter of the beam.The minimum velocity spread at maximum bunching is found to be proportional to the square of the fundamental component of rf current, up to an optimum drive level. Above this drive level the velocity spread increases rapidly with no corresponding increase in rf current. Trajectories of electrons of all initial phases are found to undergo a basic transition from nonovertaking to overtaking at a new characteristic distance &lgr;pq/4, which is given approximately by the geometric mean of the infinite beam quarter‐plasma wavelength &lgr;p/4 and the reduced (due to finite beam size) quarter‐plasma wavelength &lgr;q/4. This characteristic distance is found to be a key parameter in the prediction of velocity spread, drift length and drive for optimally bunched electron beams for use in klystron amplifiers, harmonic generators, and in linear accelerators.

ISSN:0021-8979    

DOI:10.1063/1.1708946

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

By combining internal friction and elastic‐aftereffect measurements the temperature dependence of the relaxation time for the stress‐induced migration of nitrogen in chromium was determined. The experimental results can be expressed by the diffusion equationD=D0exp (−&Dgr;H/RT) whereD0and &Dgr;Hare 1.6×10−2cm2/sec and 27 500 cal/mole, respectively. These experimentally determined constants yield an entropy of activation in general agreement with that predicted by Wert and Zener.

ISSN:0021-8979    

DOI:10.1063/1.1708947

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The set of admissible configurations and diffusive motions of chain molecules (beads and rigid links) on the quadratic lattice are considered with respect to a set of ``flip rules''; these permit configurations to change and the molecules to diffuse by flipping one bead at a time consistent with the excluded volume requirement. The set of configurations splits up into families such that configurations within a family can flip into each other but no transitions between configurations in different families are possible under the flip rules. The families are designated as mobile or sessile, the former including those that are able to diffuse to arbitrarily large distances; the sessiles must remain within a restricted region under the flip rules no matter how many flips are permitted. A complete discussion of chain configurations on a channel one link wide is given and the general situation for wider channels and the infinite plane is discussed. The importance of such considerations for entropy calculations and their possible relevance for biological phenomena are indicated.

ISSN:0021-8979    

DOI:10.1063/1.1708948

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Microwave and optical techniques have been used to measure the decay of the neutral metastable and the charged species in a flowing helium afterglow. Impurity gases, oxygen and argon, are introduced into the afterglow, and measurements of the resulting ionization and excitation yield values for the triplet metastable diffusion coefficient and three‐body combination coefficient of 490 cm2sec−1Torr and 0.25 sec−1Torr−2, respectively. In addition, the ambipolar diffusion coefficient of the molecular helium ion was found to be 724 cm2sec−1Torr. The mean helium pressure was in the range of 5 to 35 Torr and the gas nominally at room temperature. Absolute triplet metastable densities early in the afterglow were also measured.

ISSN:0021-8979    

DOI:10.1063/1.1708949

出版商:AIP    

年代:1967

数据来源: AIP