1,721,291 research outputs found
H PASSIVATION OF SI IMPURITIES IN GAAS
No full textThe equilibrium sites, vibrational frequencies, and electronic properties of interstitial H in GaAs doped with Si have been studied by first-principles calculations in the local density approximation within a supercell approach. Two different Si sites in GaAs have been examined: Si replacing a Ga atom (Si(Ga) donor) and Si replacing an As atom (Si(As) acceptor). We find that the stable configuration for the H-Si(Ga) complex is the antibonding-Si site. The lattice undergoes a large relaxation and the Si-As bond is almost broken. The stable site for the H-Si(As) complex is along the Si(As)-Ga bond. H binds to the Si and Ga atoms forming a three-center bond. In both cases the lattice relaxation is essential in order to obtain the passivation of the impurities. The computed localized vibrational frequencies and dissociation energies of the H-Si complexes agree reasonably well with experimental results
1ST PRINCIPLES CALCULATIONS OF HYDROGEN IN BULK GAAS
No full textWe present the results of first-principles calculations of the properties of neutral (H0) and charged (H+ and H-) hydrogen in bulk GaAs. The equilibrium sites are determined, and the electronic properties for the equilbrium positions are studied. H+ behaves as a deep donor and prefers to stay in a high valence charge region which includes the bond center. H- behaves as a deep acceptor and prefers the low valence charge region near a tetrahedral site. H0 has an amphoteric behaviour depending on the site it occupies. We compare our results with the results of calculations for H in Si
ATOMIC AND MOLECULAR-HYDROGEN IN GALLIUM-ARSENIDE - A THEORETICAL-STUDY
No full textWe present first-principles calculations of the properties of atomic and molecular hydrogen in pure bulk GaAs. Our results indicate that H penetrates into GaAs in atomic form. Inside GaAs, atomic H tends to form H-2 molecules in tetrahedral sites, which are deep energy wells for H-2. The H-2* defect, formed by one H in a bond-center site and one H in an adjacent tetrahedral position, has higher energy than H-2 but lower-energy barriers for diffusion. Isolated H could be present as a metastable species. We compute the stable charge state of isolated H as a function of the Fermi energy. Our results suggest that H behaves as a negative-U defect. As a consequence, isolated H is expected to be present only as a charged species (positively charged in p-doped samples, negatively charged in undoped and n-doped samples). Our conclusions are compared with experimental results and with the results of calculations for H in other semiconductors. The main features of H in GaAs are quite similar to what has been found in Si
Figure 6 in Talitrid amphipods (Crustacea: Amphipoda: Talitridae) and the driftwood ecological niche: a morphological and molecular study
No full textFigure 6. Scattergram and fitted linear regressions as in Figure 4. A2 FA, second antenna flagellum article count.Published as part of Wildish, D.J., Pavesi, L. & Ketmaier, V., 2012, Talitrid amphipods (Crustacea: Amphipoda: Talitridae) and the driftwood ecological niche: a morphological and molecular study, pp. 2677-2700 in Journal of Natural History 46 (43-44) on page 2693, DOI: 10.1080/00222933.2012.717971, http://zenodo.org/record/520221
Spectral- and time-resolved electroluminescence of silicon nanocrystals based light emitting devices
No full textIn this work we study the electroluminescence (EL) from a high efficiency multilayered
silicon nanocrystals light emitting diode. The spectral analysis of EL under dc condition shows
a spectrally modulated optical emission. Through reflectivity measurements we evaluated the
effects of interference on the EL lineshape due to device structure and ascribed the emission to
recombination in size dispersed silicon nanocrystals (Si-NCs). By studying the time resolved
current–voltage I–V and EL-V, we evidenced that injected carriers are both accumulated
separately and concurrently in Si-NCs. At the bias transition the accumulated carriers either
are extracted from the gate oxide giving rise to a short current pulse or they diffuse to large
Si-NCs giving rise to an EL overshoot which decays with μs time constant
Optical absorption and photoluminescence properties of a-Si1-xNx:H films deposited by Plasma-enhanced CVD
No full textSTRAIN AND ALLOYING EFFECTS ON THE ELECTRONIC AND VIBRATIONAL PROPERTIES OF INYAL1-YAS ON INP
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