Structural properties, electrical properties, deep traps spectra, optical properties of bulk 50mm-diameter AlN crystals prepared by physical vapour transport were studied by means of X-ray diffraction, selective etching, admittance spectroscopy, microcathodoluminescence. 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 0.65eV with low concentrations close to some 1013/cm3 and some 1015/cm3, respectively. The Fermi level was pinned near the 0.26eV electron traps. These traps were shown to give rise to a strong persistent photoconductivity and photocapacitance. The microcathodoluminescence spectra of the studied crystal were dominated by the 3.3, 4.2 and 5.5eV luminescence bands. The intensity of the strongest 3.3eV band was greatly enhanced in the vicinity of low-angle dislocation boundaries.

Deep Centers in Bulk AlN and their Relation to Low-Angle Dislocation Boundaries. A.Y.Polyakov, N.B.Smirnov, A.V.Govorkov, T.G.Yugova, K.D.Scherbatchev, O.A.Avdeev, T.Y.Chemekova, E.N.Mokhov, S.S.Nagalyuk, H.Helava, Y.N.Makarov: Physica B, 2009, 404[23-24], 4939-41