摘要:

Mg‐doped AlxGa1−xAs crystals with Al concentration 0⩽x⩽0.8 have been grown by the conventional LPE method. Doping characteristics of Mg and electrical properties of the crystals are studied using Hall measurements in the temperature range between 77 and 295 K. The results revealed are as follows. Magnesium works as an acceptor in AlxGa1−xAs. Its distribution coefficient is constant and about 0.6 for AlxGa1−xAs withx⩾0.1. Hole concentrations up to 1018cm−3are easily obtained for a highxof 0.65. The acceptor energy levelEiincreases from 18 meV in GaAs to 40 meV in Al0.8Ga0.2As. Thexdependence ofEican be explained by the difference of effective hole masses and dielectric constants between GaAs and AlAs. Hole concentration, mobility, and resistivity, as well as their temperature dependences, are presented for variousxvalues. These data show that Mg is a suitable acceptor in AlxGa1−xAs particularly with highxvalues.

ISSN:0021-8979    

DOI:10.1063/1.326162

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The use of a large‐diameter pulsed electron beam to anneal ion‐implantation damage has been studied with application to integrated‐circuit structures. The annealing of arsenic‐implantedp‐njunction diodes shows that properly selected exposure to an electron beam can anneal implant damage and provide nearly ideal device characteristics. Tests on MOS capacitor structures show that the electron beam itself introduces states at the Si‐SiO2interface but that these states can be easily annealed during the low‐temperature metal alloy cycle. The practical utilization of the concept requires an electron beam uniform over the entire wafer area.

ISSN:0021-8979    

DOI:10.1063/1.326163

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

We have studied the contrast of a stacking fault in the Laue‐Bragg case, i.e., when the wave fields incident from the defect are reflected from its surface and never propagate into the other part of the crystal. To calculate the contrast of such a defect we have computed the images by a direct integration of Takagi’s equations. We show the influence of different parameters such as the geometry of the fault, the fault vector, and the photoelectric absorption. The results are very similar to those obtained by Authier in the Laue‐Laue case and the contrast may be explained in a similar manner.

ISSN:0021-8979    

DOI:10.1063/1.326164

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The first controlled differential etching for profiling magnesium‐implanted semi‐insulating gallium phosphide is reported. Profiles of surface resistivity, mobility, and carrier concentration versus depth below the substrate surface for 129‐keV magnesium‐ion implants are obtained. Agreement was obtained with glow‐discharge optical spectroscopy data from an unannealed implanted substrate. The non‐Gaussian profiles indicate ion diffusion during annealing and possibly during implantation. Optimum procedures and techniques are developed for the substrate capping material, the anneal temperature, the capping method, and the application of Ohmic contacts. The carrier concentration of electrically active implanted magnesium ions in gallium phosphide, for a total magnesium‐ion dose of 1.0×1013/cm2, is the highest percent efficiency reported (∼44%).

ISSN:0021-8979    

DOI:10.1063/1.326165

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The eighth‐order tensors invariant under the transformations corresponding to the trigonal and hexagonal crystal classes are obtained on the basis of a group theoretic approach and the list of the independent fourth‐order elastic constants is presented.

ISSN:0021-8979    

DOI:10.1063/1.326114

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Precision optical interferometric measurements on a number of liquids at high pressure reveal pronounced nonlinear piezo‐optical (&Dgr;nversusP) behavior, but linear elasto‐optic (&Dgr;nversus &egr; where &egr; is the Eulerian strain) relationship. This paper reexamines this linear &Dgr;n‐&egr; relationship rather critically by a least‐squares analysis and it is shown that it can be used to discriminate between the various equations of state prevalent in the literature. It is found that the second‐order Murnaghan (ME2), second‐order Birch (BE2), and the Keane equations of state yield the best fits to the experimentally observed piezo‐optic data. Further, purely from thermodynamic and physical reasoning we can rule out ME2and BE2, thus leaving the Keane equation as the only equation of state among those considered that can satisfactorily describe the elastic and elasto‐optic behavior of liquids in its entire stability field. Since the various equations of state considered in this paper are also used for the study of isotropic solids as well, it is believed that the above conclusions should be valid in general for all isotropic solids and liquids.

ISSN:0021-8979    

DOI:10.1063/1.326166

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A continuum model is proposed to consider diffusion situations where distinct types of structural or point defects contribute to the overall diffusivity. With respect to structural defects, the analysis is motivated by diffusion in the presence of a continuous distribution of high‐diffusivity paths, such as grain boundaries and dislocations. With respect to point defects, the analysis is motivated by simultaneous diffusion of vacancies and interstitials, or vacancies and substitutionals. As a result of continuum modeling, the analysis is strictly valid in cases where the distribution of defects can be assumed continuous in space‐time. The model is illustrated by detailing an example: dislocation‐pipe diffusion under steady‐state conditions.

ISSN:0021-8979    

DOI:10.1063/1.326167

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

An analysis of the measurement of grain‐boundary diffusion at low temperatures by the surface‐accumulation mehod was carried out. In this method atoms are allowed to diffuse along grain boundaries from a source to a free surface where they spread out, accumulate, and are measured. The diffusion is carried out at low temperatures so that only the grain boundary and surface ’’short‐circuit paths’’ are active, and lattice diffusion is frozen out. This method is generally more sensitive than the depth profiling method for measuring grain‐boundary diffusion at low temperatures. However, the kinetics of the surface accumulation are strongly dependent on the nature of the source and sink. Treating the surface as a sink of finite capacity with a finite diffusion coefficient, diffusion analyses were developed for either a constant or an instantaneous source. Two dimensionless parameters,GandH, play important roles in determining the form of the solutions.Hinvolves the ratio of grain‐boundary capacity to surface capacity.Gis proportional to the ratio of the grain‐boundary diffusivity to that of the surface. WhenG⩽1 andH⩽1, conditions for uniform concentration on the surface and quasi‐steady‐state diffusion in the grain boundary are met, and the general solution becomes relatively simple. For a constant source, the surface concentration then obeys the relationcs=1−exp(−st), wheresis a parameter proportional to the boundary diffusivity andtis the time. The application of the analyses to a variety of diffusion systems was discussed. It was concluded that the conditions for the simple solutions to apply are not particularly stringent.

ISSN:0021-8979    

DOI:10.1063/1.326168

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Grain‐boundary diffusion rates in the gold‐silver system were measured at relatively low temperatures by the surface‐accumulation method which was analyzed in Paper I. The specimen was a polycrystalline gold film possessing columnar grains on which a silver layer was initially deposited epitaxially on one surface. During subsequent low‐temperature annealing lattice diffusion was frozen out, and diffusion then occurred along the grain boundary and free‐surface short circuits. The silver, therefore, diffused into the film from the silver layer along the boundaries, eventually reaching the opposite surface where it accumulated and was measured by Auger spectroscopy. The silver layer acted as an effective constant silver source, and grain‐boundary diffusivities were calculated from the accumulation data. However, the exact location of the effective constant source in the silver layer could not be determined and this led to an uncertainty in the values of the grain‐boundary diffusivities of a factor of 10. Lower‐ and upper‐bound values were therefore described byDb(lower bound) =7.8×10−6 exp(−0.62eV/kT) andDb(upper bound) =7.8×10−5 exp(−0.62eV/kT) cm2/s in the temperature range 30–269 °C. An examination of available grain‐boundary diffusion data (including the present) suggests a tendency for the observed activation energy to decrease with decreasing temperature, and this was ascribed to a spectrum of activated jumps in the grain boundary and/or a spectrum of grain‐boundary types in the specimen employed. The constant source behavior was tentatively ascribed, at least in part, to a grain‐boundary ’’Kirkendall effect’’ resulting from the faster diffusion of silver than gold. The work indicates a need for increased understanding of the details of grain‐boundary diffusion in alloys.

ISSN:0021-8979    

DOI:10.1063/1.326115

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Temperature‐stable surface‐acoustic‐wave (SAW) devices have been fabricated with an rf‐sputtered SiO3. film overlay onYZLiTaO2. The material properties of this composite structure relevant to surface‐acoustic‐wave propagation have been thoroughly studied. For an SiO2film thickness of approximately one‐half of an acoustic wavelength, a piezoelectric coupling coefficient of 0.014 is present and the temperature stability of phase delay is similar in magnitude to that of bulk acoustic waves inAT‐cut quartz. A variation in delay of less than one part in 105is observed over the temperature range −40 to 80 °C. The film‐overlay structure is dispersive and the nature of this dispersion has been fully characterized. The dependence of the phase and group delay on temperature and frequency has been measured. For most characteristics, theoretical as well as experimental values have been determined. In addition toYZLiTaO3, five other cuts of LiTaO3have been analyzed theoretically. To demonstrate potential applications for this structure, several practical devices have been fabricated and tested. Narrow‐band delay lines have been fabricated for use in SAW‐controlled oscillators. These oscillators showed a temperature stability nearly ten times better than similar devices fabricated onST‐cut quartz. Also, to demonstrate a wide‐bandwidth application, a 13‐bit Barker code, matched‐filter pair has been fabricated. These devices also performed well.

ISSN:0021-8979    

DOI:10.1063/1.326116

出版商:AIP    

年代:1979

数据来源: AIP