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Hydride Vapor Phase Epitaxy (HVPE) is the most popular method for fabrication of high structural quality and high-purity GaN substrates. The technology of obtaining a low level of impurities together with high crystallographic quality of HVPE-GaN crystals enables the next step, namely introducing intentional doping to the growth process and obtaining semi-insulating crystals. This work describes developing a method for incorporation of acceptors (carbon or iron) into HVPE-grown GaN while maintaining high structural quality and low level of other impurities in the material. Ammonothermally grown GaN crystals and substrates will be used as seeds. All growth processes will be carried out in a home-built quartz horizontal HVPE reactor. Methane (CH4) will be used as the precursor of carbon. The FeCl2 precursor will be created inside the reactor chamber by an HCl-stream over elemental iron. HVPE crystallization runs with different flows of acceptor precursors will be performed. HVPE-GaN:C and HVPE-GaN:Fe crystals will be characterized with X-ray diffraction, Raman spectroscopy, low-temperature photoluminescence, optical as well as transmission electron microscopies, Hall measurements, and Secondary Ion Mass Spectrometry. The properties of crystallized HVPE-GaN:C and HVPE-GaN:Fe will be compared in detail. It will be shown that concentrations of impurities (carbon or iron) in the new-grown material is always very uniform across the (0001) surface and along the c-direction. This result together with a high crystalline quality of the crystallized material will allow to obtain the semi-insulating HVPE-GaN crystals with resistivity of the order of 109 Ω.cm at room temperature.
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