摘要:

CdS layers were epitaxially grown on GaAs in an atmosphere of hydrogen gas by the close‐spaced technique. Then the thermodynamics of the reaction, the morphology, and electrical properties of the CdS epitaxial films were studied. Examinations of the temperature dependence of the evaporation rate of source CdS powder, of film growth rates, and of surface morphology demonstrated that the growth kinetics are between the mass‐transfer control case and the surface‐reaction control case, but closer to the former. The electrical properties of the films were greatly influenced by growth conditions, especially by substrate temperature. Film resistivity increased from 10−3to 1 &OHgr; cm as a function of substrate temperature, and the carrier concentration in the film increased exponentially as the temperature of the substrate was raised: Carrier concentration = 1.31×1029exp (−1.98/kTsub) cm−3. The dominant donor species in CdS films was shown to originate from the autodoping of Ga by the GaAs substrate. Electron mobility in the films also increased as the temperature of the substrate was raised, which was attributed to the superior crystallinity in the films grown at a rather high substrate temperature.

ISSN:0021-8979    

DOI:10.1063/1.1663813

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Theoretical and experimental investigations have been made on the galvanomagnetic properties in very thin single‐crystal InSb (4.6–26.4 &mgr; in thickness) at room temperature, ranging from Ohmic to high‐electric‐field regions. Two kinds of surface are prepared by chemical etching and mechanical lapping. A transverse magnetic field of up to 15 kG is applied parallel to the surface of the samples to deflect intrinsic electrons and holes to one of the surfaces. The thin sample shows a small magnetoresistance in the Ohmic region, a linear electric field dependence of the conductance in a small electric field, and a current saturation in a high electric field. From these phenomena, bulk lifetimes and surface recombination velocities are estimated. It is shown that the bulk lifetimes and the saturation current can be explained by the Auger process. Surface recombination velocity of about 104cm/sec for etched surfaces and of the order of 105cm/sec for lapped surfaces are obtained. Theoretical calculations include the case of an intermediate magnetic field which is important for InSb at room temperature.

ISSN:0021-8979    

DOI:10.1063/1.1663814

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Efficient red GaP LED's have been fabricated by compensating thepside of the junction with a donor. The observed efficiency in the diodes fabricated remains invariant over a wide range of net acceptor concentration. Utilizing the recombination kinetic analysis of Jayson, Bhargava, and Dixon, it is shown that better injection efficiencies and higher Zn&sngbnd;O complex concentrations are the cause for this invariance. The compensation technique potentially offers a commercial LPE growth process from which high‐efficiency low‐cost LED's could be fabricated.

ISSN:0021-8979    

DOI:10.1063/1.1663815

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Under short‐pulse excitation, 0.5–1.0 &mgr;s, O(III) laser emission in the visible and uv is only observed after extinction of the current pulse. The observed high gain and high power (∼100 W) of the 5592.6‐Å line is related to the afterglow character of the lasing. Two new lasing lines of O(III) have been observed at 3757.2 and 3773.8 Å. In pulsed discharges through xenon‐oxygen mixtures, laser emission from xenon occurs during the current pulse, while the lasing from oxygen occurs 0.8 &mgr;s later. The use of the O(III) laser line at 5592.6 Å for the pumping of dye lasers is suggested.

ISSN:0021-8979    

DOI:10.1063/1.1663816

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Red luminescence in CdS has been studied in as‐grown and ion‐implanted crystals. An IR band consisting of two emission bands, IR1and IR2, is produced by ion implantation. The higher‐energy band, IR1, has the same origin as the R band observed in some as‐grown crystals. A comparison of the R and IR1bands in CdS with self‐activated (SA) luminescence in ZnS and GaAs shows that they are SA luminescence at 1.7 eV at low temperatures in CdS. The temperature variations in peak energy, half‐width, and intensity of luminescence are discussed, and the behavior is explained in terms of a configurational coordinate model. A vibrational energy of 0.025 eV, which is about 70% of the LO phonon energy in CdS, is calculated for the excited state of the center. The study of the excitation dependence of the center shows that the luminescence is due to an electronic transition within a localized center and not due to a donor‐acceptor pair recombination. The center has an excitation band about 0.22 eV below the band gap. The annealing behaviors of the IR1and IR2centers are similar to each other, the bands abruptly disappear over 400°C. There are competitive phenomena between the IR1and IR2centers as to temperature and excitation‐intensity dependences. We tentatively attribute the IR2band to an aggregation defect center.

ISSN:0021-8979    

DOI:10.1063/1.1663817

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

We have studied domain nucleation phenomena in a (111)‐oriented garnet bubble film in the presence of in‐plane fields. From visual observations we have found that as the in‐plane field is lowered from saturation, a homogeneous stripe nucleation occurs at a critical easy axis bias fieldH∥n, leading to a ``mixed polarity state'' at remanence. For bias fields different fromH∥n, inhomogeneous bubble nucleation occurs which is dependent on the defect distribution in the sample and which can give rise to a bubble lattice at remanence. The bias fieldH∥ndepends on the azimuthal angle &phgr; of the in‐plane field in the sample plane; it has threefold (cos3&phgr;) and onefold (cos&phgr;) symmetry components which can be related to cubic and tilted uniaxial anisotropy, respectively. The tilt of the uniaxial anisotropy is found to be along the same direction as, but significantly larger than, the actual tilt of the crystallographic axis, perhaps indicating a large sensitivity of growth anisotropy to misalignment. An orthorhombic anisotropy component is observed in the in‐plane nucleation field. These results are compared to the results of photometric measurements of the type previously proposed by Shumate, Smith, and Hagedorn, and by Krumme, Hansen, and Haberkamp. A phase theory, modified to include finite‐thickness effects phenomenologically, is developed to determine the conditions for second‐order (stripe) nucleation in the presence of cubic, tilted uniaxial, and orthorhombic anisotropy. Analytical expressions are found forH∥nwhich can be used to evaluate the anisotropies from the data. The results are consistent with independent measurements of these anisotropies on the same specimen.

ISSN:0021-8979    

DOI:10.1063/1.1663818

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

We have calculated the total Lagrangian and Rayleigh dissipation functions for an isolated domain of arbitrary cross section in an infinite plate with perpendicular anisotropy. Variation of these functions yields a set of coupled equations describing the motion of the center of mass and the boundaryR(&phgr;) (in general noncircular) of the domain. We neglectzdependence and assume&dgr;/R≪1where &dgr; is the wall ``thickness''. The theory is applicable for applied field variations of arbitrary speed and magnitude. For uniform field pulses, the equations reduce to the Callen‐Josephs theory in the weak‐pulse limit. For pulses >2&pgr;Ms/&agr;, where &agr; is the Gilbert parameter, the behavior again tends to be linear with, generally, a greatly reduced apparent mobility, while in the transition region 2&pgr;Ms&agr;<Hp<2&pgr;Ms/&agr;, the predicted behavior is highly nonlinear with an oscillatory substructure which causes an alternating sequence of collapse‐noncollapse regions in the conventional plot of inverse pulse length vs pulse height. Translatory motion of the domain in a field gradient is also highly nonlinear reducing to ``effective mass'' behavior only whenR H′≪4&pgr;M&agr;. An approximate prediction of the theory is that regardless of the magnitude of the pulse gradient (i) the net displacement is given byx0≈&mgr;WR(dH/dx)t0, where &mgr;Wis the wall mobility and (ii) the minimum elapsed time for a displacement is ≈ &tgr;A=(Ms/2K)(R2/&dgr;2)(&ggr;&agr;)−1, whereKis the anisotropy constant and &ggr; the gyromagnetic ratio. Finally, the theory predicts a finite displacement in a directiontransverseto the sense of the field gradient.

ISSN:0021-8979    

DOI:10.1063/1.1663819

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Mo¨ssbauer and crystallographic investigations were carried out on DyFe3−xNixcompounds crystallizing in the PuNi3type of structure. The hyperfine field observed at the iron sites shows a maximum atx=0.75. The 12‐line spectrum observed at room temperature corresponding to the two different kinds of iron in the structure collapsed into a single six‐line pattern at 4.2 K. Lattice parametercshows a rapid decrease whenxis increased beyond 2.0, but no such behavior was found in thealattice parameter. The results of the x‐ray and Mo¨ssbauer data are explained in terms of site preference and nonlocalized transition‐metal moments, respectively.

ISSN:0021-8979    

DOI:10.1063/1.1663820

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Microwave components incorporating ferrite elements are primarily waveguide devices. Success with these devices has yielded a wide range of useful commercial products. However an underdeveloped area for microwave ferrite application is microwave optics. Due to the complexity of design and observed anomalous behavior, ferrites have not found popularity as refraction elements. The present paper presents an initial assault into the analysis of refracting ferrite prisms and lenses. The anisotropic indices of refraction and angles of deviation were calculated for an isosceles ferrite prism magnetized in three orthogonal directions and the focal lengths of an axially magnetized thin double‐convex ferrite lens were evaluated for various values of saturation magnetization.

ISSN:0021-8979    

DOI:10.1063/1.1663821

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Electric, magnetic, and electron paramagnetic resonance (EPR) measurements have been performed on thin EuO films prepared either by reactive evaporation of Eu at 400°C or by oxidation of a Eu metal thin film at 200–250°C. The films obtained by reactive evaporation have electrical and magnetic properties very similar to those reported for EuO single crystals of various degrees of nonstoichiometry. The films prepared by oxidation of Eu films at 200–250°C are characterized by a much higher‐valued Curie temperature (Tc≃148 K), while their resistivity is in the range 10−2−1 &OHgr; cm. The EPR signal can be attributed to Eu spins, which shows that in these films there exist fluctuations of Eu doping due to nonstoichiometry. We analyzed the high concentration of oxygen vacancies in the bound magnetic polaron (BMP) model. A high level of defects and oxygen vacancies, inhomogeneously distributed in the film, can account for both their electrical and magnetic properties.

ISSN:0021-8979    

DOI:10.1063/1.1663822

出版商:AIP    

年代:1974

数据来源: AIP