Magnetic properties of Mn and Fe-implanted p-GaN

The structural and magnetic properties of p-GaN implanted with high doses o f Mn+ or Fe+ (0.1-5 at%) and subsequently annealed at 700-1000 degreesC wer e examined by transmission electron microscopy, selected-area diffraction p atterns, X-ray diffraction and SQUID magnetometry. The implanted samples sh owed paramagnetic behavior on a large diamagnetic background signal for imp lantation doses below 3 at% Mn or Fe. At higher doses the samples showed si gnatures of ferromagnetism with Curie temperatures < 250 K for Mn and < 150 K for Fe implantation. The structural analysis of the Mn-implanted GaN sho wed regions consistent with the formation of GaxMn1-xN platelets occupying similar to5% of the implanted volume. An estimate of similar to (5.5 +/- 1. 9)mu (B) per Mn was obtained, consistent with the expected value (5.0) for a half-filled shell. The formation of secondary phases such as MnxGay or Mn xNy was excluded by careful diffraction analysis. The implantation process may have application in forming selected-area contact regions for spin-pola rized carrier injection in device structures and in enabling a quick determ ination of the Curie temperatures in dilute magnetic semiconductor host mat erials.