Microstructure of the deep level defect E1/E2 in 6H silicon carbide (Abstract)

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Zn-vacancy related defects in ZnO grown by pulsed laser deposition

Undoped and Ga-doped ZnO (002) films were grown c-sapphire using the pulsed laser deposition (PLD) method. Znvacancy related defects in the films were studied by different positron annihilation spectroscopy (PAS). These included Doppler broadening spectroscopy (DBS) employing a continuous monenergetic positron beam, and positron lifetime spectroscopy using a pulsed monoenergetic positron beam attached to an electron linear accelerator. Two kinds of Znvacancy related defects namely a monovacancy and a divacancy were identified in the films. In as-grown undoped samples grown with relatively low oxygen pressure P(O2)≤1.3 Pa, monovacancy is the dominant Zn-vacancy related defect. Annealing these samples at 900 oC induced Zn out-diffusion into the substrate and converted the monovacancy to divacancy. For the undoped samples grown with high P(O2)=5 Pa irrespective of the annealing temperature and the as-grown degenerate Ga-doped sample (n=1020 cm-3), divacancy is the dominant Zn-vacancy related defect. The clustering of vacancy will be discussed.published_or_final_versio

Deep level transient spectroscopy study of particle irradiation induced defects in n-6H-SiC (Abstract)

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Thermal evolution of defects in undoped zinc oxide grown by pulsed laser deposition

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Electric-field distribution in Au–semi-insulating GaAs contact investigated by positron-lifetime technique

Positron-lifetime spectroscopy has been used to investigate the electric-field distribution occurring at the Au–semi-insulating GaAs interface. Positrons implanted from a 22Na source and drifted back to the interface are detected through their characteristic lifetime at interface traps. The relative intensity of this fraction of interface-trapped positrons reveals that the field strength in the depletion region saturates at applied biases above 50 V, an observation that cannot be reconciled with a simple depletion approximation model. The data, are, however, shown to be fully consistent with recent direct electric-field measurements and the theoretical model proposed by McGregor et al. [J. Appl. Phys. 75, 7910 (1994)] of an enhanced EL2+ electron-capture cross section above a critical electric field that causes a dramatic reduction of the depletion region’s net charge density. Two theoretically derived electric field profiles, together with an experimentally based profile, are used to estimate a positron mobility of ∼95±35 cm2 V-1 s-1 under the saturation field. This value is higher than previous experiments would suggest, and reasons for this effect are discussed.published_or_final_versio

Spatial distribution of carrier concentration in un-doped GaN film grown on sapphire (Abstract)

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Ultraviolet Lasing Characteristics of ZnS Microbelt Lasers

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The Zn-vacancy Related Green Luminescence and Donor–acceptor Pair Emission in ZnO Grown By Pulsed Laser Deposition

postprin

Photoluminescence and lasing characteristics of single nonpolar GaN microwires

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Nature of red luminescence band in research-grade ZnO single crystals: A “self-activated” configurational transition

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