| Popis: |
Structural properties, electrical properties, deep traps spectra, optical properties of bulk 50-mm-diameter AlN crystals prepared by physical vapor transport (PVT) were studied by means of X-ray diffraction, selective etching, admittance spectroscopy, microcathodoluminescence (MCL). The crystals had a low dislocation density with dislocations forming a well defined cellular structure. The dominant electron traps had the ionization energy of 0.26 and 0.65 eV with low concentrations close to some 1013 cm−3 and some 1015 cm−3, respectively. The Fermi level was pinned near the 0.26 eV electron traps. These traps were shown to give rise to a strong persistent photoconductivity and photocapacitance. MCL spectra of the studied crystal were dominated by the 3.3, 4.2 and 5.5 eV luminescence bands. The intensity of the strongest 3.3 eV band was greatly enhanced in the vicinity of low-angle dislocation boundaries. |
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