摘要:

The AlxGa1−xAs/GaAs heterostructure system is potentially useful material for high‐speed digital, high‐frequency microwave, and electro‐optic device applications. Even though the basic AlxGa1−xAs/GaAs heterostructure concepts are understood at this time, some practical device parameters in this system have been hampered by a lack of definite knowledge of many material parameters. Recently, Blakemore has presented numerical and graphical information about many of the physical and electronic properties of GaAs [J. S. Blakemore, J. Appl. Phys.53, R123 (1982)]. The purpose of this review is (i) to obtain and clarify all the various material parameters of AlxGa1−xAs alloy from a systematic point of view, and (ii) to present key properties of the material parameters for a variety of research works and device applications. A complete set of material parameters are considered in this review for GaAs, AlAs, and AlxGa1−xAs alloys. The model used is based on an interpolation scheme and, therefore, necessitates known values of the parameters for the related binaries (GaAs and AlAs). The material parameters and properties considered in the present review can be classified into sixteen groups: (1) lattice constant and crystal density, (2) melting point, (3) thermal expansion coefficient, (4) lattice dynamic properties, (5) lattice thermal properties, (6) electronic‐band structure, (7) external perturbation effects on the band‐gap energy, (8) effective mass, (9) deformation potential, (10) static and high‐frequency dielectric constants, (11) magnetic susceptibility, (12) piezoelectric constant, (13) Fro¨hlich coupling parameter, (14) electron transport properties, (15) optical properties, and (16) photoelastic properties.Of particular interest is the deviation of material parameters from linearity with respect to the AlAs mole fractionx. Some material parameters, such as lattice constant, crystal density, thermal expansion coefficient, dielectric constant, and elastic constant, obey Vegard’s rule well. Other parameters, e.g., electronic‐band energy, lattice vibration (phonon) energy, Debye temperature, and impurity ionization energy, exhibit quadratic dependence upon the AlAs mole fraction. However, some kinds of the material parameters, e.g., lattice thermal conductivity, exhibit very strong nonlinearity with respect tox, which arises from the effects of alloy disorder. It is found that the present model provides generally acceptable parameters in good agreement with the existing experimental data. A detailed discussion is also given of the acceptability of such interpolated parameters from an aspect of solid‐state physics. Key properties of the material parameters for use in research work and a variety of AlxGa1−xAs/GaAs device applications are also discussed in detail.

ISSN:0021-8979    

DOI:10.1063/1.336070

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The construction of composition profiles from x‐ray diffraction peaks is an important and reliable technique, but it has not been widely adopted because it required hours of computer time and/or complicated optimization routines. The method proposed here utilizes an easily evaluated analysis of the diffraction peak. It is applicable to thin films and thick specimens for which the variation with composition of lattice parameters, linear absorption coefficient, and reflectivity are known. A deconvolution scheme is outlined that includes corrections for the instrumental broadening and singlet or doublet radiation.

ISSN:0021-8979    

DOI:10.1063/1.336121

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The method of optimal truncation is developed and applied to a variety of rotationally symmetric defects in elastic materials. Results are presented for oblate and prolate spheroidal voids, cracks, irregularly shaped voids, and compound inclusions. Most of the examples are in the frequency domain, but samples of time‐domain calculations are included. Physical interpretations of some features of the calculated amplitudes are given. Checks on accuracy of the results are emphasized and implemented.

ISSN:0021-8979    

DOI:10.1063/1.336122

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Certain two‐dimensional symmetrical systems of magnetic conductors, consisting of semi‐infinite and finite plates are examined using a mapping method. Four examples are studied.

ISSN:0021-8979    

DOI:10.1063/1.336123

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Data are presented on the energy extraction from a transversely excited atmospheric CO2laser amplifier by a 1.1‐ns pulse consisting of an adjustable number of lines which are generated by a multiline oscillator of a new design. An increase in energy extraction of 95% with respect to single‐line extraction was achieved with a pulse consisting of up to six lines in the 10.6‐&mgr;m branch. Energy extraction at a fixed number of lines was not very sensitive to their spectral distribution. We observed a maximum increase of about 8% when the lines were spread over the 00°1–10°0 vibrational band. This indicates a slight preference for small &Dgr;jvalues in the rotational relaxation processes.

ISSN:0021-8979    

DOI:10.1063/1.336124

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Catastrophic degradation related to local heating in GaAlAs visible lasers occasionally occurs under relatively low optical output power. To develop highly reliable lasers, we used laser Raman spectroscope with an argon ion laser focused at about 1 &mgr;m&bartil; to evaluate the local operating temperature rise not only at the facet surface, but also along the striped active region. The local operating temperature rise in the vicinity of the facet’s active region increased exponentially up to 200 °C when the optical output power was 30 mW/facet. This high temperature causes the rapid formation of a dark region and final catastrophic degradation. The calculated temperature rise along the striped active region is about one‐half of that of the facet. The internal operating temperature is far higher than the average temperature measured by the thermal resistance method, which is considered to be a large influence on the lifetime and activation energy of lasers in practical applications.

ISSN:0021-8979    

DOI:10.1063/1.336125

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Atmospheric pressure operation of a KrF laser is suitable for large‐aperture laser modules in which several technical limitations on the ICF driver design are overcome by the use of aerodynamic windows instead of the conventional solid optical windows. We experimentally studied atmospheric‐pressure operation of the KrF laser pumped by 50‐ns electron beams. For a 1‐atm mixture of Kr and F2without diluent, a specific output energy of 4.2 J/1 was obtained with an intrinsic efficiency of 5%, which was comparable to that from normal 10% Kr mixture. According to the results of fluorescence measurements, a large amount of Kr2F* is formed via three‐body collisional quenching by high‐concentration Kr even in the atmospheric‐pressure mixture. Code calculations indicate that a higher excitation rate improves the intrinsic efficiency by reducing three‐body quenching especially in Kr‐rich mixtures, and that a specific energy in excess of 10 J/1 is realizable.

ISSN:0021-8979    

DOI:10.1063/1.336126

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A method is presented for obtaining optical parameters that are relevant to problems of radiative transfer in such fields as polyester fiber insulation and the passage of radiation through aerosol clouds. The concept of the asymmetry factor is generalized to include nonspherical particles in order to calculate the ratio of the power of radiated light into the forward direction to the power of backscattering light. The geometry for scattering from an infinite cylinder randomly oriented is discussed and related to the problem of identifying the forward and backward directions. This geometry is used to calculate the asymmetry factor versus the angle which the cylinder axis makes with the direction of incidence. The asymmetry factor is also plotted as a function of the size parameter of the cylinder for random orientations of the cylinder.

ISSN:0021-8979    

DOI:10.1063/1.336127

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Experimental results are presented which show that the dynamic Stark effect significantly reduces the small‐signal gain (in discharge‐excited CO2) and absorption (in unexcited CO2) at the line center of 4.3‐&mgr;m laser lines directly coupled to 10.4‐&mgr;m sequence‐band pump transitions. In unexcited CO2, population transfer by the pump radiation is negligible and the influence of coherent effects can be observed unambiguously. The results of comparing experiment and theory in this simple case are used to modify a rate‐equation model of the 4.3‐&mgr;m gain dynamics, and the modified calculations are shown to be in good agreement with measured 4.3‐&mgr;m gain coefficients.

ISSN:0021-8979    

DOI:10.1063/1.336128

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Gaussian functions characterized by a radius of gyration are shown to approximate the intensity of light diffracted at small angles by opaque single‐oriented microparticles. Procedures are presented for obtaining the radii of gyration.

ISSN:0021-8979    

DOI:10.1063/1.336129

出版商:AIP    

年代:1985

数据来源: AIP