Preparation of wurtzite GaN-based magnetic alloy semiconductors by molecular beam epitaxy

This paper describes the preparation of hexagonal GaN:Mn and GaN:Fe epilayers by molecular beam epitaxy with very high concentrations of transition metal ions which are sufficient to exhibit magnetic orders. We have found that the growth window to obtain epilayers without a macroscopic second phase is relatively large for the GaN:Mn compared with the GaN:Fe. Magnetization data have showed that GaN:Mn epilayers are primarily paramagnetic with the ferromagnetic spin exchange represented by the paramagnetic Curie temperature theta (p) = 20 K. The effective spin number would be S approximate to 2.5. The GaN:Fe epilayers exhibit superparamagnetic behavior which presumably arises from Fe and/or FeN crystallites. (C) 2001 Elsevier Science B.V. All rights reserved.