1,721,028 research outputs found
Compensating defects in Si-doped AlN bulk crystals
No full textThe rather low n-type conductivity observed in. Si-doped sublimation-grown AlN bulk crystals is explained by the formation of high concentrations of compensating defects. The model is based on the experimental verification of a shallow impurity band formed by Si donors and the presence of acceptor-like electron traps within 1 eV below the conduction band edge. Further it is suggested that the majority of the Si donors is compensated by deep acceptors in the lower half of the band gap. This compensation model is an alternative to the controversially discussed assumption of Si DX center formation. (c) 2007 Elsevier B.V. All rights reserved
Coloration of Wide-Bandgap Semiconductors Originating from Particle Plasmons
No full textDepending on growth and annealing conditions ZnO crystals can show a reddish coloration clearly deviating from the normal, colorless transparency. The additional broad near-edge absorption is observed when particles of few nanometer diameter are present in the crystals. Excitation of plasmons in Zn nanoparticles can explain this absorption
Boron- and stoichiometry-related defect engineering during B(2)O(3)-free GaAs crystal growth
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Thermoluminescence in a scanning electron microscope
No full textThe capabilities of thermoluminescence (TL) performed in a scanning electron microscope using the electron beam for excitation at low temperatures are presented. This method allows spatially as well as spectrally resolved TL. In the case of low excitation densities and short excitation times, the primary electron scattering volume determines the spatial resolution of the subsequent measurement. The potential of this technique is demonstrated for the characterization of bulk and heteroepitaxial AlN. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.3000455
n-type conductivity in sublimation-grown AIN bulk crystals
No full textAlN crystals grown by physical vapour-phase transport in the presence of a SiC doping source possess n-type conductivity. The net donor concentration attains up to mid 10(17) cm(-3). The investigation reveals shallow donors forming an impurity band and acceptor-like electron traps at about 0.5 eV below the conduction band edge. Thermal electron emission from these traps is responsible for the observed n-type conductivity. The shallow donors are suggested to be due to Si atoms on Al sites. The majority of them is assumed to be compensated by deep acceptors in the lower half of the band gap
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