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Applied Physics Reviews — 1988


Band‐edge nonlinearities in direct‐gap semiconductors and their application to optical bistability and optical computing

S. W. Koch, N. Peyghambarian, and H. M. Gibbs

J. Appl. Phys. 63, R1 (1988); http://dx.doi.org/10.1063/1.340098 (12 pages)

Online Publication Date: 12 December 2006

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Nonlinear optical properties of laser‐excited semiconductors are discussed, and the applications to optical bistability and optical logic are reviewed. The physical origin of the nonlinearities is analyzed in terms of the many‐body interactions in the system of electron‐hole pairs, causing effects such as plasma screening of the Coulomb interaction, band‐gap renormalization, and band filling. Theoretical results for absorption and refractive‐index spectra are compared to experimental data obtained for room‐temperature GaAs and other semiconductors. The experimental and theoretical results for dispersive optical bistability in semiconductors are summarized, and recent experiments on optical logic gating and pattern recognition are discussed.
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42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

RETM5 and RE2TM17 permanent magnets development

Kaplesh Kumar

J. Appl. Phys. 63, R13 (1988); http://dx.doi.org/10.1063/1.341084 (45 pages)

Online Publication Date: 12 December 2006

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RETM5 and RE2TM17 (RE=rare earth, TM=transition metal) permanent magnets are discussed in this review. The scientific and technological considerations which have guided their development are described. Along with a discussion of the various research efforts reported in the literature, they help establish the framework within which most of the work can be integrated and understood. In regard to the RETM5 alloys, the review limits itself to the technologically significant SmCo5 materials; others are discussed minimally, and only to the extent that they contributed to overall magnet development efforts. Likewise, from among the fabrication technologies, the review is limited to those processes which have been demonstrated as capable of producing magnets in bulk useful form. Areas covered in this review include phase diagrams, crystal structures, magnetocrystalline anisotropy, coercivity mechanisms, fabrication technologies, processing‐microstructure‐property interrelationships, and thermal effects related to stability of magnet flux. Directions for future, additional work are discussed briefly as well.
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07.55.Db Generation of magnetic fields; magnets
85.70.-w Magnetic devices
75.50.Cc Other ferromagnetic metals and alloys

Rapid isothermal processing

R. Singh

J. Appl. Phys. 63, R59 (1988); http://dx.doi.org/10.1063/1.340176 (56 pages)

Online Publication Date: 12 December 2006

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The physics and technology of a relatively new, short‐time, thermal processing technique, namely rapid isothermal processing (RIP), based on incoherent sources of light for the fabrication of semiconductor devices and circuits, are reviewed in this paper. Low‐cost, minimum overall thermal budget, low‐power consumption, and high throughput are some of the attractive features of RIP. The discussion of RIP, in the context of other thermal processes, history, operating principles, different types of RIP systems, various applications of RIP using single processing steps, and novel applications of RIP, including in situ processing and multistep processing, is described in detail. Current trends are in the direction of RIP‐dominated silicon integrated circuit fabrication technology that can lead to the development of the most advanced three‐dimensional integrated circuits suitable for applications such as parallel processing and radiation hardening. RIP is not only a superior alternative to furnace processing, but it is also the only way to perform certain crucial steps in the processing of compound semiconductor devices such as high‐mobility transistors, resonant tunneling devices, and high‐efficiency solar cells. Development of more accurate temperature measurement techniques and theoretical studies of heat transfer and other fundamental processes are needed. Dedicated equipment designed for a specific task coupled with in situ processing capabilities will dominate the future direction of RIP.
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85.40.Hp Lithography, masks and pattern transfer
85.30.De Semiconductor-device characterization, design, and modeling

Coupling of guided modes in thin films with surface corrugation

S. R. Seshadri

J. Appl. Phys. 63, R115 (1988); http://dx.doi.org/10.1063/1.340381 (32 pages)

Online Publication Date: 12 December 2006

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Two guided modes in a grounded, thin, dielectric film waveguide having a periodic corrugation of the interface between the film and the cover can interact selectively in the neighborhood of a particular frequency. Five different theories exist for the investigation of this interaction. The first three are small amplitude theories which assume that the amplitude of the corrugation relative to the thickness of the film is small and the third and the fourth theories are large amplitude theories which do not make such an assumption. In the small amplitude theories, solutions are sought as a perturbation of ideal normal modes and boundary conditions are applied on the average flat surface. The first small amplitude theory makes use of quasioptical considerations and the other two small amplitude theories employ wave‐theoretical techniques. All three theories lead to identical coupled mode equations governing the interaction. The first large amplitude theory is based on an expansion in terms of local normal modes and is applicable for a grating with a smooth profile. The second large amplitude theory is applicable for a lamellar grating and it makes use of a model of a repetitively mismatched transmission line. The various intrinsic dephasing mechanisms are explained. The large amplitude theories are able to account for the dephasing effects due to the finite (nonvanishing) depth and the finite (noninfinite) length of the corrugations. Some aspects of passive devices and some theoretical considerations of active devices using corrugated waveguides are reviewed. The transmission line model is able to take into account the end effects. For the mode of operation considered, there are no end effects and the overall contribution of the vertical discontinuities vanish for the lamellar grating.
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84.40.Az Waveguides, transmission lines, striplines
77.55.-g Dielectric thin films

X rays from z‐pinches on relativistic electron‐beam generators

N. R. Pereira and J. Davis

J. Appl. Phys. 64, R1 (1988); http://dx.doi.org/10.1063/1.341808 (27 pages)

Online Publication Date: 12 December 2006

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This review summarizes recent experimental data on imploding z‐pinches and their radiation output, and gives an overview of theoretical issues concerning radiation production in the pinch plasma. A z‐pinch plasma is created when the current from a fast, powerful electrical generator compresses and heats a small amount of material between the electrodes. The hot, dense plasma emits copious amounts of radiation extending from the visible to the x‐ray region. With a 10‐TW electrical discharge the radiative power may be a few TW, with an energy per pulse of up to tens of kilojoules. Our interest is mainly in the photons with energy around 1 keV, which are useful in x‐ray lithography, microscopy, surface studies, and other applications.
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52.55.Ez Theta pinch
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
07.85.-m X- and γ-ray instruments

Diluted magnetic semiconductors

J. K. Furdyna

J. Appl. Phys. 64, R29 (1988); http://dx.doi.org/10.1063/1.341700 (36 pages)

Online Publication Date: 12 December 2006

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We review the physical properties of diluted magnetic semiconductors (DMS) of the type AII1−xMnxBVI (e.g., Cd1−xMnxSe, Hg1−xMnxTe). Crystallographic properties are discussed first, with emphasis on the common structural features which these materials have as a result of tetrahedral bonding. We then describe the band structure of the AII1−xMnxBVI alloys in the absence of an external magnetic field, stressing the close relationship of the sp electron bands in these materials to the band structure of the nonmagnetic AIIBVI ‘‘parent’’ semiconductors. In addition, the characteristics of the narrow (nearly localized) band arising from the half‐filled Mn 3d5 shells are described, along with their profound effect on the optical properties of DMS. We then describe our present understanding of the magnetic properties of the AII1−xMnxBVI alloys. In particular, we discuss the mechanism of the Mn++‐Mn++ exchange, which underlies the magnetism of these materials; we present an analytic formulation for the magnetic susceptibility of DMS in the paramagnetic range; we describe a somewhat empirical picture of the spin‐glasslike freezing in the AII1−xMnxBVI alloys, and its relationship to the short range antiferromagnetic order revealed by neutron scattering; and we point out some not yet fully understood questions concerning spin dynamics in
DMS revealed by electron paramagnetic resonance. We then discuss the sp‐d exchange interaction between the sp band electrons of the AII1−xMnxBVI alloy and the 3d5 electrons associated with the Mn atoms. Here we present a general formulation of the exchange problem, followed by the most representative examples of its physical consequences, such as the giant Faraday rotation, the magnetic‐field‐induced metal‐to‐insulator transition in DMS, and the properties of the bound magnetic polaron. Next, we give considerable attention to the extremely exciting physics of quantum wells and superlattices involving DMS. We begin by describing the properties of the two‐dimensional gas existing at a DMS interface. We then briefly describe the current status of the AII1−xMnxBVI layers and superlattices (systems already successfully grown; methods of preparation; and basic nonmagnetic properties of the layered structures). We then describe new features observed in the magnetic behavior of the quasi‐two‐dimensional ultrathin DMS layers; and we discuss the exciting possibilities which the sp‐d exchange interaction offers in the quantum‐well situation. Finally, we list a number of topics which involve DMS but which have not been explicitly covered in this review such as elastic properties of DMS, DMS‐based devices, and the emerging work on diluted magnetic semiconductors other than the AII1−xMnxBVI alloys—and we provide relevant literature references to these omitted topics.
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75.50.Pp Magnetic semiconductors

Native defects in gallium arsenide

J. C. Bourgoin, H. J. von Bardeleben, and D. Stiévenard

J. Appl. Phys. 64, R65 (1988); http://dx.doi.org/10.1063/1.341206 (28 pages)

Online Publication Date: 12 December 2006

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We describe information which has been obtained on point defects detected in various types of GaAs materials using electron paramagnetic resonance as well as electrical and optical techniques. From a comparison of their characteristics and those of simple intrinsic defects (As and Ga interstitials, vacancies and antisites) it is concluded that native defects are not simple intrinsic defects, with the exception of the antisites, but complexes formed by the interaction of such defects between themselves or with impurities. Particular emphasis is given to the As antisite complexed with an As interstitial, the so‐called EL2 defect which plays a major role in the electrical properties of bulk materials. Differential thermal analysis, positron annihilation, and x‐ray diffraction demonstrate that bulk materials contain a large concentration of vacancy‐related defects and As precipitates located along dislocations which play the role of gettering centers. Presumably, bulk materials also contain other As clusters of various sizes although only the smallest ones (EL2) have been detected. All these As clusters are sources of As interstitials which play an important role in thermal treatments. As to semi‐insulating materials, their electrical properties result mainly from the compensation between the double donor, called EL2, associated with the As antisite and the double acceptor ascribed to the Ga antisite.
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61.72.J- Point defects and defect clusters
61.72.S- Impurities in crystals

Atom diffusion and impurity‐induced layer disordering in quantum well III‐V semiconductor heterostructures

D. G. Deppe and N. Holonyak, Jr.

J. Appl. Phys. 64, R93 (1988); http://dx.doi.org/10.1063/1.341981 (21 pages)

Online Publication Date: 12 December 2006

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The process of impurity‐induced layer disordering (IILD) or layer intermixing, in AlxGa1−xAs‐GaAs quantum well heterostructures (QWHs) and superlattices (SLs), and in related III‐V quantum well heterostructures, has developed extensively and is reviewed. A large variety of experimental data on IILD are discussed and provide newer information and further perspective on crystal self‐diffusion, impurity diffusion, and also the important defect mechanisms that control diffusion in AlxGa1−xAs‐GaAs, and in related III‐V semiconductors. Based on the behavior of Column III vacancies and Column III interstitials, models for the crystal self‐diffusion and impurity diffusion that describe IILD are reviewed and discussed. Because impurity‐induced layer disordering has proved to be an important method for III‐V quantum well heterostructure device fabrication, we also review the application of IILD to several different laser diode structures, as well as to passive waveguides. We mention that it may be possible to realize even more advanced device structures using IILD, for example, quantum well wires or quantum well boxes. These will require an even greater understanding of the mechanisms (crystal processes) that control IILD, as well as require more refined methods of pattern definition, masking procedures, and crystal processing.
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68.35.Fx Diffusion; interface formation
66.30.J- Diffusion of impurities
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
85.30.De Semiconductor-device characterization, design, and modeling
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