Crystallization of semi-insulating HVPE-GaN with solid iron as a source of dopants

Gallium nitride crystals were grown by hydride vapor phase epitaxy using solid iron as a source of dopants. Three crystal growth processes were performed at constant HCl flow over the solid iron and with different gallium chloride flows. High structural quality ammonothermal GaN was used as seed material. No yellow luminescence and only weak near band edge luminescence were visible in all grown crystals. A sharp peak was observed at 1.298 eV. This was shown before as an intrinsic transition of Fe impurity in GaN. The grown crystals were highly resistive at room temperature. High-temperature Hall effect measurements revealed n-type conductivity with activation energy equal to 1.8 eV. Secondary ion mass spectrometry indicated the presence of manganese in all three samples. The concentration of manganese was always higher than concentration of iron in the doped GaN.