Paper MI+EM-WeA4
Ferromagnetism in Gd- and Si-co-implanted GaN

Wednesday, November 11, 2009, 3:00 pm, Room C1

Ion implantation has been studied as a magnetic ion incorporation method in semiconductor materials for spintronic applications due to excellent control over the amount of the implanted ion and the resultant magnetic properties of the implanted material. GaN thin films grown via metal-organic chemical vapor deposition (MOCVD) were co-implanted with Gd⁺ ions with an energy of 155 keV and dose of 2.75 × 10¹⁰ cm^-2 and Si⁴⁺ ions with energies of 5 keV and 40 keV and corresponding doses of 8 × 10¹¹ cm^-2 and 3.6 × 10¹² cm^-2. Before annealing, x-ray diffraction measurements revealed that the implanted GaN thin films exhibited no secondary phase formation or clustering effects attributable to Gd. Superconducting quantum interference device (SQUID) magnetometer measurements indicated that a Gd- and Si-co-implanted GaN thin film exhibited about an order of magnitude higher magnetic moment than a Gd-implanted GaN thin film. Both of these thin films displayed ferromagnetic ordering and Curie temperatures above room temperature. The co-implanted GaN thin film also demonstrated a larger magnetic moment than a Gd- and Si-co-doped GaN thin film grown via molecular beam epitaxy (MBE) while possessing a smaller Gd concentration. The orientation of the applied magnetic field with respect to the thin film surface was seen to have an effect on the measured magnetic properties of the thin films. This orientation dependence may help elucidate the relationship between the defects produced by the implantation process and the ferromagnetic ordering exhibited by these materials.