Realization of High‐Resistive Ni‐Doped GaN Crystal by Hydride Vapor‐Phase Epitaxy

Herein, high‐resistivity GaN is studied for use as an epitaxial substrate in lateral power devices. Fe‐, C‐, Mn‐, and Zn‐doped GaN monocrystals have high resistivity at a doping concentration of ≈1 × 1018 cm−3. However, a low doping concentration is preferred for growing GaN monocrystals; therefore, other dopants for GaN that yield high resistivity at a doping concentration less than 1 × 1018 cm−3 must be identified. Herein, NiCl2 is used as a precursor to grow Ni‐doped GaN monocrystals on GaN substrates via hydride vapor‐phase epitaxy. Two Ni‐doped GaN substrates with Ni concentrations corresponding to 2.7 × 1017 and 2.9 × 1018 cm−3 are obtained by varying the partial pressure of NiCl2. The resistivity of Ni‐doped GaN monocrystals is measured as a function of temperature using Hall effect measurements. The GaN monocrystals doped with 2.7 × 1017 cm−3 of Ni have a higher resistivity than those doped with 2.9 × 1018 cm−3 of Ni at 600–900 K. Charge‐neutrality calculations have shown that the depth of the Ni acceptor level in GaN is 1.4–1.5 eV, indicating that Ni‐doped GaN monocrystals have high resistivity owing to the deep acceptor level of Ni. This study shows that NiCl2 is used as a precursor to grow Ni‐doped GaN monocrystals on GaN substrates via hydride vapor‐phase epitaxy. Hall effect measurements show that the Ni‐doped GaN monocrystals are semi‐insulating. Also, this study reveals the origin of the high resistivities of the Ni‐doped GaN monocrystals by charge‐neutrality calculations.