A.Ya. Polyakov, N.B. Smirnov, A.V. Govorkov, I.A. Belogorokhov, K.D. Scherbachev, V.T. Bublik, O.A. Avdeev, T.Yu. Chemekova, E.N. Mokhov, S.S. Nagalyuk, H. Helava, Yu.N. Makarov

A.Ya. Polyakov, e-mail: aypolyakov@gmail.com, N.B. Smirnov, A.V. Govorkov, I.A. Belogorokhov, (OAO Giredmet); K.D. Scherbachev, V.T. Bublik, (National Research University «MISiS»); O.A. Avdeev, T.Yu. Chemekova, e-mail: chemekova@n-crystals.fi.ru, E.N. Mokhov, S.S. Nagalyuk, H. Helava, (Nitride Crystals JSC); Yu.N. Makarov, e-mail:makarov@semicrys.fi.ru, Nitride Crystals JSC, Gallium-N JSC

Structural and electrical properties of bulk AlN crystals synthesized by physical vapor transport (PVT) have been studied by means of X-ray diffraction, conductivity versus temperature measurements, admittance spectroscopy (AS), photoinduced current transient spectroscopy (PICTS), selective etching and microcathodoluminescence (MCL) spectra and imaging measurements. We show that the crystals consist of large domains with dimensions of some 100 micron and a dislocation density of 10²-10⁴ cm^-2 inside the domains. The electrical properties in the seed part of the crystals are determined by defects with the level near E_c-0.3 eV (most likely Si donors) and deep traps with the level near E_c-0.7 eV, as determined from conductivity, AS and PICTS measurements. In addition, the MCL spectra revealed the presence of deep traps giving rise to the MCL band near 3.3 eV whose density is enhanced in the vicinity of intergrain boundaries. The resistivity of the crystal increases as one moves from the seed part grown on SiC substrate to the tail part grown on AlN.

Aluminum nitride, sublimation method, single crystals, conductivity, deep traps.

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