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Raman spectra of Ga1−xMnxN crystals grown by the resublimation method have been investigated. New bands around 300 and 667 cm−1, as well as a broad structure near 600 cm−1, not observed in undoped GaN have been found. The temperature dependence of major Raman bands has been measured. The simple model of GaN lattice dynamics has been presented, and the observed bands have been assigned to disorder-activated phonon modes, in good agreement with the calculated phonon density of states.

Crystallization of GaN by hydride vapor phase epitaxy (HVPE) on ammonothermally grown GaN seed crystals is described. The initial growth conditions for HVPE are determined and applied for further bulk growth. Smooth GaN layers up to 1.1 mm thick and of excellent crystalline quality, without cracks, and with low dislocation density are obtained. Preparation of the free-standing HVPE-GaN crystal by slicing and structural and optical quality of the resulting wafer are presented.

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