Growth of Fe-Doped Thick GaN Layers for Preparation of Semi-Insulating GaN Substrates

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Vapor-phase epitaxy of Fe-doped thick GaN layers was performed using GaCl, NH3 and FeCl2 as source gases on (0001) sapphire and (111)A GaAs substrates with the aim of preparing semi-insulating (SI) GaN substrates. On sapphire, the resistivity of the GaN layer increased with increasing FeCl2 input partial pressure. A 12-µm-thick SI GaN layer showing a resistivity of 3.0×109 Ω cm at room temperature was successfully grown by compensating for background donors. In contrast, the resistivity of the GaN layers grown on the GaAs substrate remained low (on the order of 10-2 Ω cm) even though the same growth conditions were used as on the sapphire substrate. Secondary ion mass spectroscopy (SIMS) measurements suggested that the presence of As vapor-species caused by the degradation of the substrate hindered Fe from becoming incorporated into GaN.