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Semi-insulating GaN by Fe-Doping in Hydride Vapor Phase Epitaxy Using a Solid Iron Source

Using a solid iron source, Fe-doping during GaN growth by hydride vapor phase epitaxy (HVPE) on sapphire was realized. The doping concentration could be controlled by varying the gas flow over the iron source and was verified by secondary ion mass spectrometry (SIMS). After removal of the sapphire substrate, semi-insulating freestanding (FS) GaN of high quality was achieved, with a resistivity of up to 4 · 10 Ωcm at room temperature. For Fe-doped samples on sapphire, a partial release of the high, compressive strain at room temperature has been observed. The measurement of the full-width-halfmaximum (FWHM) of high resolution X-ray (HRXRD) rocking curves was hampered by the serious wafer bow for both GaN on sapphire and freestanding GaN. Nevertheless, we observed values for FS-GaN as low as 40 arcsec and 80 arcsec for the (002) and (102)reflection, respectively.