Teacher Training To Identify Students With Dyslexia. Implementation Of Accommodations To Help Students Be Successful

This curriculum-based capstone provides educators with an in-depth review of how teachers are being trained to identify students with dyslexia. It can be used as a guide to the implementation of accommodations to help students with dyslexia be successful in the classroom. The research question for this capstone is: What is being done for students with dyslexia in our schools? A review of the literature included the definition dyslexia through misconceptions, diagnosis procedures and brain imaging techniques. Dyslexia is identified in the classroom through a person’s rights, the stigma associated with dyslexia and a teacher’s role in identification. The strategy section of the literature review goes over various strategies and accommodations put in place that are helpful for a student with dyslexia. The research method was designed find out what teachers already knew about dyslexia through a survey and a completion of observations and interviews to determine successful techniques in a specialized classroom. A compilation of this information was used to determine how teachers and school districts can improve dyslexia awareness and training in their schools. Several strategies and accommodations such as the Wilson-Reading program, Rave-O, Read Live, Learning Ally and Orton-Gillingham have proven to be successful. The outcome of this curriculum-based capstone has reviewed a current look into how schools are dealing with dyslexia and what they can do to improve

Temperature dependence of the band gap shrinkage due to electron-phonon interaction in undoped n-type GaN

The photoluminescence spectra of band-edge transitions in GaN is studied as a function of temperature. The parameters that describe the temperature dependence red-shift of the band-edge transition energy and the broadening of emission line are evaluated using different models. We find that the semi-empirical relation based on phonon-dispersion related spectral function leads to excellent fit to the experimental data. The exciton-phonon coupling constants are determined from the analysis of linewidth broadening

Strain-free bulk-like GaN grown by hydride-vapor-phase-epitaxy on two-step epitaxial lateral overgrown GaN template

Crack-free bulk-like GaN with high crystalline quality has been obtained by hydride-vapor-phase-epitaxy (HVPE)growth on a two-step epitaxial lateral overgrown GaN template on sapphire. During the cooling down stage, the as-grown 270-μm-thick GaN layer was self-separated from the sapphire substrate. Plan-view transmission electron microscopyimages show the dislocation density of the free-standing HVPE-GaN to be ∼2.5×10 exp 7  cm exp −2 on the Ga-polar face. A low Ga vacancy related defect concentration of about 8×10 exp 15 cm exp−3 is extracted from positron annihilation spectroscopy data. The residual stress and the crystalline quality of the material are studied by two complementary techniques. Low-temperature photoluminescence spectra show the main neutral donor bound exciton line to be composed of a doublet structure at 3.4715 (3.4712) eV and 3.4721 (3.4718) eV for the Ga- (N-) polar face with the higher-energy component dominating. These line positions suggest virtually strain-free material on both surfaces with high crystalline quality as indicated by the small full width at half maximum values of the donor bound exciton lines. The E1(TO) phonon mode position measured at 558.52 cm exp −1 (Ga face) by infrared spectroscopic ellipsometry confirms the small residual stress in the material, which is hence well suited to act as a lattice-constant and thermal-expansion-coefficient matched substrate for further homoepitaxy, as needed for high-quality III-nitride device applications.Peer reviewe

Free carrier effects in gallium nitride epilayers: the valence band dispersion

The dispersion of the A-valence-band in GaN has been deduced from the observation of high-index magneto-excitonic states in polarised interband magneto-reflectivity and is found to be strongly non-parabolic with a mass in the range 1.2-1.8 m_{e}. It matches the theory of Kim et al. [Phys. Rev. B 56, 7363 (1997)] extremely well, which also gives a strong k-dependent A-valence-band mass. A strong phonon coupling leads to quenching of the observed transitions at an LO-phonon energy above the band gap and a strong non-parabolicity. The valence band was deduced from subtracting from the reduced dispersion the electron contribution with a model that includes a full treatment of the electron-phonon interaction.Comment: Revtex, 4 pages, 5 figure

Elimination of Lateral Resistance and Current Crowding in Large-Area LEDs by Composition Grading and Diffusion-Driven Charge Transport

Peer reviewe

Filtering of Defects in Semipolar (11−22) GaN Using 2-Steps Lateral Epitaxial Overgrowth

Good-quality (11−22) semipolar GaN sample was obtained using epitaxial lateral overgrowth. The growth conditions were chosen to enhance the growth rate along the [0001] inclined direction. Thus, the coalescence boundaries stop the propagation of basal stacking faults. The faults filtering and the improvement of the crystalline quality were attested by transmission electron microscopy and low temperature photoluminescence. The temperature dependence of the luminescence polarization under normal incidence was also studied

Implementation of a Monte Carlo method to model photon conversion for solar cells.

A physical model describing different photon conversion mechanisms is presented in the context of photovoltaic applications. To solve the resulting system of equations, a Monte Carlo ray-tracing model is implemented, which takes into account the coupling of the photon transport phenomena to the non-linear rate equations describing luminescence. It also separates the generation of rays from the two very different sources of photons involved (the sun and the luminescence centers). The Monte Carlo simulator presented in this paper is proposed as a tool to help in the evaluation of candidate materials for up- and downconversion. Some application examples are presented, exploring the range of values that the most relevant parameters describing the converter should have in order to give significant gain in photocurrent

Direct observation of threading dislocations in GaN by high-resolution Z-contrast imaging

Wide gap nitride semiconductors have attracted significant attention recently due to their promising performance as short-wavelength light emitting diodes (LEDs) and blue lasers. One interesting issue concerning GaN is that the material is relatively insensitive to the presence of a density of dislocations which is six orders of magnitude higher than that for III-V arsenide and phosphide based LEDs. Although it is well known that these dislocations originate at the film-substrate interface during film growth, thread through the whole epilayer with line direction along and are perfect dislocations with Burgers vectors of a, c, or c+a, the reason why they have such a small effect on the properties of GaN is unclear. To develop a fundamental understanding of the properties of these dislocations, the core structures are studied here by high resolution Z-contrast imaging in a 300kV VG HB603 scanning transmission electron microscope (STEM) with a resolution of 0.13 nm. As the Z-contrast image is a convolution between the probe intensity profile and the specimen object function, it is possible to obtain more detailed information on the specimen object function, i.e. the structure, through maximum entropy analysis (the maximum entropy technique produces the ``most likely`` object function which is consistent with the image)

Wafer-scale selective area growth of GaN hexagonal prismatic nanostructures on c-sapphire substrate

Selective area growth of GaN nanostructures has been performed on full 2" c-sapphire substrates using Si3N4 mask patterned by nanoimprint lithography (array of 400 nm diameter circular holes). A new process has been developed to improve the homogeneity of the nucleation selectivity of c-oriented hexagonal prismatic nanostructures at high temperature (1040\circ C). It consists of an initial GaN nucleation step at 950 \circ C followed by ammonia annealing before high temperature growth. Structural analyses show that GaN nanostructures are grown in epitaxy with c-sapphire with lateral overgrowths on the mask. Strain and dislocations are observed at the interface due to the large GaN/sapphire lattice mismatch in contrast with the high quality of the relaxed crystals in the lateral overgrowth area. A cathodoluminescence study as a function of the GaN nanostructure size confirms these observations: the lateral overgrowth of GaN nanostructures has a low defect density and exhibits a stronger near band edge (NBE) emission than the crystal in direct epitaxy with sapphire. The shift of the NBE positions versus nanostructure size can be mainly attributed to a combination of compressive strain and silicon doping coming from surface mask diffusion