摘要:

This paper presents an analysis of nonlinear interaction between extraordinary waves propagating perpendicular to the static magnetic field in a cold homogeneous magnetoplasma. It is first shown that the synchronism conditions for wave/wave interaction can be met over wide ranges of parameters. A theory of the interaction based on cold plasma theory is then described which yields a closed‐form solution for signal growth by the mechanism of parametric amplification. Numerical solutions are presented for the growth rate, and associated frequencies and wavenumbers, over a range of magnetoplasma parameters. The relevance of these results to laboratory and space plasma experimentation, and to verification of the theory, is discussed.

ISSN:0021-8979    

DOI:10.1063/1.1658171

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Foils of Al, Mg, Mo, Pt, Au, and MYLAR were bombarded with known fluxes of ions (3H,4He,22Ne,37Ar,85Kr), and accelerated to 1–40 keV in an electromagnetic isotope separator to determine the usefulness of a hypothetical experiment to bring home a sample of solar wind by exposing foils to the solar plasma current outside the earth's geomagnetic cavity. The amounts retained in such foils after bombardment and after subjecting them to particular heating cycles in vacuum and in air (1 atm) were determined. The problems of the loss of ions in space during the proposed space experiment and of extraction of ions in the laboratory subsequent to recovery were thus studied. Aluminum seems to be an acceptable collector material for solar‐wind ions. The trapping efficiency for other materials studied is variable and appreciably smaller than unity in some cases. However, since commercial aluminum can contain significant amounts of trapped rare gases, care must be taken to prepare the collector surfaces in their absence.

ISSN:0021-8979    

DOI:10.1063/1.1658172

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The effect of fast‐neutron irradiation on infrared attenuation in single‐crystal GaAs has been investigated. Bothn‐ andp‐type materials of several dopant concentrations were exposed to seven fluences of fast neutrons (> 10 keV) from 5×1014to 1.5×1018neutrons/cm2. Infrared transmission was measured before and after exposure. At low fluences, the free‐carrier absorption of all samples was reduced by neutron irradiation. At the higher neutron fluences, an absorption process which showed no structure and varied approximately as the square of the photon energy was observed to dominate the free‐carrier absorption. This absorption increased linearly with fast neutron fluence and was the same for all samples studied independent of impurity type and initial concentration. The results are in agreement with a neutron‐produced spike absorption mechanism proposed by McNichols and Ginell.

ISSN:0021-8979    

DOI:10.1063/1.1658173

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The effect of a mixed crystal transition zone (grading) on the perfection of crystals grown by epitaxial deposition onto substrates of differing lattice parameter and expansion coefficient is considered. The number of misfit dislocations required to compensate lattice mismatch at the growth temperature and magnitude of bending stresses which develop during subsequent cooling have been computed as a function of the width of the transition zone &dgr;. These results have been applied to the case of GaP grown onto GaAs seeds. Using a simple model for lattice displacements, it is predicted that grading does not reduce the number of misfit dislocations but merely distributes them over the width &dgr; so that the density is reduced in proportion to &dgr;−1. The bending stresses in the grown layer are shown to be highly dependent on the width of the transition zone and thickness of the grown layer. Moreover, for a given seed thickness and zone width there is an optimum thickness for the growth layer for which the bending stress is smallest.

ISSN:0021-8979    

DOI:10.1063/1.1658174

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Homogeneous polycrystalline InAs1−xPxalloys have been prepared by a halogen vapor‐transport closed‐tube technique over the entire range of composition. Electroreflectance measurements were made at room temperature by the electrolyte method which showed that theE1andE1+&Dgr;1transition energies vary in a concave upwards manner, while theE0′,E2, andE2+&dgr; transition energies vary linearly with composition. Wavelength‐modulated reflectance measurements on semiconducting alloys above the fundamental edge are reported for the first time. These data, taken at room and liquid‐nitrogen temperatures, confirm the interpretation placed on the variation of the electroreflectanceE1peaks. TheE1spin‐orbit splitting (&Dgr;1) remains almost constant in energy asxis increased from InAs and then falls rapidly to the InP value. A similar shape is obtained for &Dgr;1from a k·p calculation for the alloy band structure, which shows that a movement of the transitions in k space is probably responsible for this behavior.

ISSN:0021-8979    

DOI:10.1063/1.1658175

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Data are presented which show that three distinct optical recombination transitions occur inp‐type GaAs:Si. These recombination transitions are band to band, conduction band to shallow acceptor, and conduction band to deep acceptor. With adequate pumping, as shown on ultrathin platelets, laser emission due to any of these transitions is possible, depending upon the cavity resonator gain profile and the crystal doping concentration. The effect of compensating Si donors in the crystal upon the wavelength of emission is illustrated. The unusually broad spontaneous linewidth ofp‐type GaAs:Si demonstrated here, along with the very large spatial spread of injected carriers in a GaAs:Si solution‐grownp‐njunction, is argued as being the limiting factors to stimulated emission in junction structures.

ISSN:0021-8979    

DOI:10.1063/1.1658176

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The electron‐mirror microscope (EMM) has been used to study photosensitivenpn‐type junctions in heat‐treated epitaxial PbS films. The EMM indicated variations in junction symmetry and strength on a much smaller scale than previously observed with a light‐spot scanning technique. In addition, the variations observed were found to correlate with surface topography. Regions of high junction density that have nearly zero photovoltaic response due to cancellation effects, were clearly resolved with the EMM.

ISSN:0021-8979    

DOI:10.1063/1.1658177

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The set of optical constants of germanium reported by Marton and Toots, from 8 to 25 eV, have been assessed and found to be internally consistent to within ±5%. An extension of thenandkvalues up to photon energy of 100 eV using Hunter'skvalues also has been studied. The analysis consisted of an internal consistency check by applying the Kronig‐Kramers dispersion relations to the optical constants and an evaluation and study of the optical and electron oscillator‐strength distributions. From an application of the general sum rules to the oscillator‐strength distribution, the computed effective number of electrons per germanium atom are in general agreement with an extrapolation of Manson and Cooper's calculation.

ISSN:0021-8979    

DOI:10.1063/1.1658178

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Data are presented showing the variation at 77°K in GaAs laser photon energy, and the laser recombination process, as a function of doping concentration from the lowest dopings now possible to the highest donor, acceptor, and donor‐acceptor (compensated) dopings which still yield crystals of laser quality. GaAs is shown to be capable of laser operation over a range exceeding 1200 Å (&lgr;min≤7880 Å to 9100 Å ≤ &lgr;max). Experimental data onn‐type crystals are used to approximate the position of the Fermi level. Data onp‐type and compensated crystals are used to approximate the depth of donor tail states involved in laser action. These results agree reasonably well with the values calculated from the metallic hydrogen model. Laser photon‐energy data on uniformly dopedp‐type crystals are presented which indicate the extent to which acceptor states involved in laser operation penetrate into the forbidden gap.

ISSN:0021-8979    

DOI:10.1063/1.1658179

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

It is shown that self‐absorbed emission lines due to a bound exciton and its phonon satellite may be used to determine (1) the absorption coefficient at the wavelength of bound exciton emission line and (2) the nature of the impurity binding the exciton. The technique is described and is illustrated by experimental results on CdS.

ISSN:0021-8979    

DOI:10.1063/1.1658180

出版商:AIP    

年代:1969

数据来源: AIP