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Sumathi, R. Radhakrishnan (2014): Native seeding and silicon doping in bulk growth of AlN single crystals by PVT method. In: Physica Status Solidi (C) - Current Topics in Solid State Physics, Vol. 11, No. 3-4: pp. 545-548
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Homo-epitaxial growth of AlN crystals using native seeds prepared from our hetero- epitaxial AlN/SiC template crystals has been successfully carried out. Single crystals of acceptable structural properties with XRD-RC FWHM of 150 arcsec, Raman E2(high) phonon mode FWHM of 9 cm^-1 and with low concentrations of background impurities (below the detection limit of EPMA)were obtained. An effort has been made to obtain n-type conductivity in the PVT grown AlN single crystals through intentional Si-doping during bulk growth. The investigations using EPMA and micro-Raman measurements confirm that it is possible to incorporate intentionally the Si atoms in the bulk AlN host lattice without any kind of Si inclusions or precipitates. Structural quality of the Si-doped crystals was almost same as that of the native seed crystal. Si-doping induces a compressive strain in the doped AlN crystals as seen from the 5 cm^-1 shift (blue shift) in the Raman E2(high)peak position. EPR measurement gives first evidence of the presence of shallow level Si donor in the grown crystal, though the freecarrier concentrations are quite low for a semiconductor doping.