Making ferromagnetic semiconductors out of Ⅲ-Ⅴ nitride semiconductors

摘要

Transition metal doped Ⅲ-Ⅴ nitrides including Mn- or Cr-doped GaN and InN are grown by molecular beam epitaxy. Structural, electronic and magnetic properties have been investigated. Cr-doped GaN shows room temperature ferromagnetism. Bulk sensitive high-energy x-ray photoemission spectroscopy is performed at SPring-8 to elucidate electronic structure of Cr-doped GaN. It is found that the doped Cr contributes to form gap states, which pin the Fermi level. The gap state is attributed to Ga 4s originated state caused by strong hybridization between Cr 3d and band electrons of host GaN. InN-based system was grown by low temperature molecular beam epitaxy. Highly Mn-doped InN shows spin-glass states. Anti-ferromagnetic interaction between Mn ions in InN was suggested. Contrary to the Mn-doped InN, Cr-doped InN shows ferromagnetic property at room temperature.