Mg-doped GaN activated with Ni catalysts

We deposited Ni catalytic films with different thicknesses onto the as-grown Mg-doped GaN epitaxial layers and subsequently annealed the samples by conventional furnace annealing. It was found that surface of the Ni catalytic films became rough with numerous island structures after thermal treatment. With a 10 nm-thick Ni film, it was found that we achieved a hole concentration of 4.35 × 1017 cm−3 with a 400 °C annealing. Without the Ni catalytic film, we could achieve p-type conduction only when the annealing temperature was equal to or larger than 600 °C. SIMS results show that H concentration was reduced and a certain amount of Ni atoms seem to penetrate into the GaN epitaxial layers after annealing. Furthermore, it was found that we could only achieve p-GaN with high hole concentration at the sample surface by using the Ni catalytic films.