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We report on the crystallinity, N incorporation efficiency, optical properties, and electrical properties of N and Te codoped ZnO films grown by plasma-assisted molecular-beam epitaxy. Te improves the surface morphology and roughness of ZnO films in terms of both streak reflection high energy electron diffraction pattern and atomic force microscopy observations. Also, N and Te codoping is helpful to improve the crystallinity and N incorporation efficiency simultaneously. We found that; (a) narrower x-ray linewidth and higher N concentration were obtained by codoping. (b) Nitrogen related emission lines including donor-acceptor pair and acceptor-bound exciton dominantly emerged in photoluminescence spectra. (c) Codoping enhanced the carrier compensation of native donors in ZnO films and suppressed the dislocation scattering. As a consequence, we concluded that N and Te codoping is very effective for the growth of reliable p-type ZnO films which fulfill the controversial requirements; high N concentration and high crystallinity, simultaneously. [ABSTRACT FROM AUTHOR]

Presents a study which discussed the photoluminescence spectra of deformed silicon-germanium alloy. Description of the photoluminescence technique; Experimental details; Results.

Optical and electrical properties of fresh dislocations in GaN bulk crystals deformed plastically at elevated temperatures were reviewed. A dislocation band model was proposed. The fresh dislocations of ( a /3) [ 1 2 ¯ 10 ] -type edge dislocations on the ( 10 1 ¯ 0 ) prismatic plane induced several photoluminescence peaks at around 1.8, 1.9 and 2.4 eV, which implies the formation of radiative recombination centers of the dislocations. Simultaneously, near-band-edge (3.48 eV) photoluminescence intensity decreased remarkably for a high-density of non-radiative recombination centers originating in deformation-induced abundant Ga-vacancy related clusters. The intensity variation of yellow luminescence with plastic deformation and subsequent annealing did not relate to the native property of dislocations. Variation of optical absorption dependent on the strain in plastically deformed GaN was understood in a model of the Franz–Keldysh effect by the electric fields associated with charged dislocations (~5.8 e/nm). Scanning spreading resistance microscopic images showed many spots with high conductivity around the induced dislocations, showing electrical conduction along dislocations according to the Frenkel–Poole mechanism. [ABSTRACT FROM AUTHOR]

Abstract: Fresh (a/3) dislocations on the prismatic plane were introduced into GaN bulk crystals by plastic deformation at 950°C. Photoluminescence (PL) studies at 11K showed that the near band edge (3.48eV) luminescence intensity decreased drastically in the deformed GaN, attributed to the introduction of a high-density of non-radiative recombination centers during plastic deformation. The yellow band (2.22eV) luminescence decreased by plastic deformation, while several luminescence bands centered at 1.79, 1.92, 2.4 and 2.8eV developed. The dependence of PL features on deformation and annealing indicates that yellow luminescence is not related to the native structure of dislocations in GaN. [Copyright &y& Elsevier]

The yield strength of GaN bulk crystals determined directly by means of compressive deformation is around 100–200 MPa in the temperature range 900–1000°C. On the basis of the observed temperature and strain rate dependencies of yield stress, the dislocation mobility at elevated temperatures is evaluated. Deformed GaN shows a drastic reduction of PL intensity, suggesting that newly formed dislocations give rise to non-radiative recombination centers. [Copyright &y& Elsevier]

Highlights: [•] We form an intense micro- and near-field light probe for conventional thin specimens under TEM, by which both structural and optical properties are obtained in-situ, with a high energy resolution simultaneously with a high spatial resolution. [•] The light probes can be applied to in-situ TEM of the structural variation of nanostructures via photo-excitation, as well as photoluminescence (PL) and Raman spectroscopies. [•] The light probes will be applied to determine photo-excitation effects of optoelectronic materials successively from a microscopic level to a nanoscopic one. [Copyright &y& Elsevier]

Abstract: Optical properties of fresh dislocations, (a/3)[112¯0]-type edge dislocations on the (11¯00) prismatic plane, introduced into GaN by plastic deformation at elevated temperatures were investigated by photoluminescence and optical absorption measurements. Plastic deformation acts as an effective passivation, leading to remarkable reduction of near-band-edge photoluminescence intensity centered at 3.48eV and noticeable red-shift of the optical absorption edge. In a model of the Franz–Keldysh effect, the induced edge dislocations posses nonradiative trap sites around 3e/c along their core, resulting in the reduction of free-carrier concentration. Also, the induced dislocations give rise to some luminescence peaks in the energy range 1.7–2.4eV, differing from the yellow luminescence, which implies the formation of radiative recombination centers by the dislocations. [Copyright &y& Elsevier]

Dislocations generated by indentation and subsequent annealing at elevated temperatures up to 800 °C in high quality (0001) wafers of ZnO single crystals were investigated by transmission X-ray topography and photoluminescence. Damages induced by indentation in ZnO wafers were guessed to lead to dislocated regions from X-ray topographic images. PL intensities of 3.36 eV near-band edge peak and 2.4 eV deep emission band in ZnO decreased drastically, with increasing in annealing temperature up to 800 °C, irrespective of dislocated or non-dislocated regions. The development of a new emission band 2.8–3.0 eV was found in non-damaged ZnO through annealing at 700 and 800 °C, which suggests that dislocations suppress the development of the new peak. [ABSTRACT FROM AUTHOR]

An arbitrary number of dislocations were freshly introduced in wurtzite ZnO bulk single crystals by plastic deformation at high temperatures (923–1123 K), and the optical properties were examined by photoluminescence spectroscopy. ZnO, including a high density (more than 109 cm-2) of dislocations, showed excitonic light emission with photon energies of 3.100 and 3.345 eV, as well as their LO-phonon replicas, at a temperature of 11 K, and the intensities increased with increasing dislocation density. [ABSTRACT FROM AUTHOR]

Abstract: Transmission X-ray topography of the Ga-doped ZnTe crystals grown by the double crucible liquid encapsulated pulling (DCP) method is presented. The results show that dislocation density increases with growth direction from top to bottom. Photoluminescence (PL) intensity of the (A 0, X) emission clearly decreases with the growth direction from top to bottom. Therefore, it is concluded that the PL intensity of the (A 0, X) peak decreases with increasing dislocation density. [Copyright &y& Elsevier]