Optical Dielectric Functions of III-V Semiconductors in Wurtzite Phase

Optical properties of semiconductors can exhibit strong polarization dependence due to crystalline anisotropy. A number of recent experiments have shown that the photoluminescence intensity in free standing nanowires is polarization dependent. One contribution to this effect is the anisotropy of the dielectric function due to the fact that most nanowires crystalize in the wurtzite form. While little is known experimentally about the band structures wurtzite phase III-V semiconductors, we have previously predicted the bulk band structure of nine III-V semiconductors in wurtzite phase.Here, we predict the frequency dependent dielectric functions for nine non-Nitride wurtzite phase III-V semiconductors (AlP, AlAs, AlSb, GaP, GaAs, GaSb, InP, InAs and InSb). Their complex dielectric functions are calculated in the dipole approximation by evaluating the momentum matrix elements on a dense grid of special k-points using empirical pseudopotential wave functions. Corrections to the momentum matrix elements accounting for the missing core states are made using a scaling factor which is determined by using the optical sum rules on the calculated dielectric functions for the zincblende polytypes. The dielectric function is calculated for polarizations perpendicular and parallel to the c-axis of the crystal

Balancing the Scales: Reforming Georgia\u27s Common Law in Evaluating Restrictive Covenants Ancillary to Employment Contracts

Crafting effective and enforceable restrictive covenantsancillary to employment contracts has befuddled andvexed attorneys, courts, and businesses in Georgia fordecades. Tracing its development through more than fourhundred years of judicial decisions, Georgia\u27s common lawhas grown increasingly contradictory, confusing, andconvoluted. Until the passage of the Restrictive CovenantAct, Georgia judges grew increasingly hostile to restrictivecovenants; however, they failed to maintain a coherent setof guidelines for evaluating such covenants. TheRestrictive Covenant Act marks a turning point in Georgiaemployment law, and this Note provides a defense of theAct.The Restrictive Covenant Act is designed to attractbusinesses to Georgia, boost employment, raise wages, andincrease the standard of living. The Act significantlyshifts public policy by adding pro-firm policies to balanceits predominantly pro-employee common law. A carefulstudy of the Act\u27s provisions shows that it will not undulyharm employees\u27 interests in Georgia. Additionally, this Note urges Georgia courts to further improve the Act\u27sfairness and efficacy by adopting a per se rule that wouldprotect employees who fall outside the defined parametersof the Act. This per se rule would act as an additionalpolicing agent for employers who try to enforce restrictivecovenants against this class of employees who may havestrong regional or community ties but lack bargainingpower or company influence. This Note finally provides acompelling look into the inspiration for and developmentof the Restrictive Covenant Act: An interview with GeorgiaGeneral Assembly Representative Wendell Willard,Chairman of the House Judiciary Committee and authorof the Restrictive Covenant Act

Predicted band structures of III-V semiconductors in wurtzite phase

While non-nitride III-V semiconductors typically have a zincblende structure, they may also form wurtzite crystals under pressure or when grown as nanowhiskers. This makes electronic structure calculation difficult since the band structures of wurtzite III-V semiconductors are poorly characterized. We have calculated the electronic band structure for nine III-V semiconductors in the wurtzite phase using transferable empirical pseudopotentials including spin-orbit coupling. We find that all the materials have direct gaps. Our results differ significantly from earlier {\it ab initio} calculations, and where experimental results are available (InP, InAs and GaAs) our calculated band gaps are in good agreement. We tabulate energies, effective masses, and linear and cubic Dresselhaus zero-field spin-splitting coefficients for the zone-center states. The large zero-field spin-splitting coefficients we find may lead to new functionalities for designing devices that manipulate spin degrees of freedom

Quantum wires from coupled InAs/GaAs strained quantum dots

The electronic structure of an infinite 1D array of vertically coupled InAs/GaAs strained quantum dots is calculated using an eight-band strain-dependent k-dot-p Hamiltonian. The coupled dots form a unique quantum wire structure in which the miniband widths and effective masses are controlled by the distance between the islands, d. The miniband structure is calculated as a function of d, and it is shown that for d>4 nm the miniband is narrower than the optical phonon energy, while the gap between the first and second minibands is greater than the optical phonon energy. This leads to decreased optical phonon scattering, providing improved quantum wire behavior at high temperatures. These miniband properties are also ideal for Bloch oscillation.Comment: 5 pages revtex, epsf, 8 postscript figure

The binary fraction in the globular cluster M10 (NGC 6254): comparing core and outer regions

We study the binary fraction of the globular cluster M10 (NGC 6254) as a function of radius from the cluster core to the outskirts, by means of a quan- titative analysis of the color distribution of stars relative to the fiducial main sequence. By taking advantage of two data-sets, acquired with the Advanced Camera for Survey and the Wide Field Planetary Camera 2 on board the Hubble Space Telescope, we have studied both the core and the external regions of the cluster. The binary fraction is found to decrease from 14% within the core, to 1.5% in a region between 1 and 2 half-mass radii from the cluster centre. Such a trend and the derived values are in agreement with previous results ob- tained in clusters of comparable total magnitude. The estimated binary fraction is sufficient to account for the suppression of mass segregation observed in M10, without any need to invoke the presence of an intermediate-mass black hole in its centre.Comment: Accepted for publication in ApJ (22 pages, 7 figures, 3 tables

Ultra-Transparent Antarctic Ice as a Supernova Detector

We have simulated the response of a high energy neutrino telescope in deep Antarctic ice to the stream of low energy neutrinos produced by a supernova. The passage of a large flux of MeV-energy neutrinos during a period of seconds will be detected as an excess of single counting rates in all individual optical modules. We update here a previous estimate of the performance of such an instrument taking into account the recent discovery of absorption lengths of several hundred meters for near-UV photons in natural deep ice. The existing AMANDA detector can, even by the most conservative estimates, act as a galactic supernova watch.Comment: 9 pages, Revtex file, no figures. Postscript file also available from http://phenom.physics.wisc.edu/pub/preprints/1995/madph-95-888.ps.Z or from ftp://phenom.physics.wisc.edu/pub/preprints/1995/madph-95-888.ps.

Painting 1 Enoch: Biblical Interpretation, Theology, and Artistic Practice

This article inaugurates a new approach to biblical interpretation that involves close collaboration on a particular text between a biblical interpreter (Philip Esler) and a practicing artist (Angus Pryor) culminating in the production of works of art that generate a new understanding of the text in question. This approach reflects the recent scholarly interest in how artists who paint biblical scenes are active interpreters of biblical texts. Here the text selected is 1 Enoch, while the artworks in question are four 2 x 2 meter paintings, in oil on canvas, that depict pivotal scenes from that text. The collaboration draws on Ethiopian tradition reflecting the scriptural status and widespread influence of 1 Enoch in Ethiopia and the fact that the complete text of the work was only preserved there until its rediscovery in modern times. The interpretative process includes a focus on the original meaning of 1 Enoch, which then influences the creation of artworks laden with theological meaning. This approach is equally available to interpreters more interested in the contemporary (rather than the historical) meaning of other biblical and extra-biblical texts where the connection with national traditions, if present, may be quite different