MOCVD-grown GaN n-type epilayers were implanted with 150keV Co+ and Cr+ ions at different fluences at room temperature. Co+ was implanted at 3x1016 and 5×1016 ions/cm2 and samples rapid-thermal-annealed at 700, 800 and 900°C for 5 minutes, while Cr+ was implanted at 3x1016 ions/cm2 and annealed at 800 and 900°C for 2 minutes. Diffraction patterns of implanted samples showed satellite peaks at the lower side of the main GaN (0002) reflection and these were assigned to implantation induced-damage and the formation of Ga1−xCoxN or Ga1−xCrxN phases. The coercivity (Hc) at 5K from SQUID for Co+ implanted GaN at 3x1016 ions/cm2 was 275 Oe and that at 5x1016 ions/cm2 was 600 Oe. For Cr+ implanted GaN at 3x1016 ions/cm2, Hc was 175 Oe. At the same dose of Cr+ and Co+ implanted ions, the saturation magnetization (Ms) values were almost similar. But after annealing at 900°C, the Ms value of Cr+ implanted GaN was higher than that of Co+ implanted at 5K. For Co+ implanted GaN, magnetization was retained up to 370K while in Cr+ implanted GaN, magnetization was retained above 380K. These findings are the highest reported Curie temperatures for Co+ and Cr+ implanted GaN diluted magnetic semiconductors.
Part of the book: Ion Implantation