Development of Semi-Insulating gallium nitride layers on native substrates by magnesium ion implantation and Ultra-High-Pressure annealing

In the presented research, we explore the possibility of modifying the electrical properties of ammonothermal gallium nitride substrates through ion implantation of magnesium and ultra-high-pressure annealing (UHPA). The goal is to achieve a semi-insulating gallium nitride template on a highly conducting gallium nitride substrate. The substrates are implanted with magnesium ions to create a reservoir of magnesium atoms near the surface. By annealing the samples at high temperatures (∼1450 °C), the aim is to achieve magnesium doping by diffusion from the implanted region. Secondary ion mass spectrometry reveal that the diffusion of magnesium extended up to 12 µm towards the bulk of the sample with a constant concentration of 2-3 × 1018 cm-3. High-resolution X-ray diffraction measurements confirm that the high structural perfection of ammonothermal gallium nitride substrates was restored after the UHPA, and the implantation-induced damage was removed from the crystals. Transmission electron microscopy is used to observe defects in the crystal structure at the atomic level. The segregation of magnesium isn’t observed, indicating a high rate of magnesium activation after annealing according to literature. To assess the electrical properties of the implanted and annealed samples, Hall measurements is performed. The results show successful fabrication of a semi-insulating layer.