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

This paper describes the preparation of hexagonal GaN:Mn and GaN:Fe epilaye rs by molecular beam epitaxy with very high concentrations of transition me tal ions which are sufficient to exhibit magnetic orders. We have found tha t 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 temperatu re 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.