Magnetic properties of Mn and Fe-implanted p-GaN

The structural and magnetic properties of p-GaN implanted with high doses of Mn+ or Fe+ (0.1-5 at%) and subsequently annealed at 700-1000 degreesC were examined by transmission electron microscopy, selected-area diffraction patterns, X-ray diffraction and SQUID magnetometry. The implanted samples showed paramagnetic behavior on a large diamagnetic background signal for implantation doses below 3 at% Mn or Fe. At higher doses the samples showed signatures of ferromagnetism with Curie temperatures 250 K for Mn and 150 K for Fe implantation. The structural analysis of the Mn-implanted GaN showed 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 MnxNy was excluded by careful diffraction analysis. The implantation process may have application in forming selected-area contact regions for spin-polarized carrier injection in device structures and in enabling a quick determination of the Curie temperatures in dilute magnetic semiconductor host materials.