Invited Paper MI-ThA6
Optimal Dopant Control of High-Tc Diluted Magnetic Semiconductors via Subsurfactant Epitaxy or n-p co-doping*

Thursday, October 18, 2007, 3:40 pm, Room 619

Recent developments of diluted magnetic semiconductors (DMS) seem to suggest that one must rely on nano-phase separations inside the DMS films of III-V and column-IV semiconductors in order to achieve high magnetic ordering temperatures (Tc>300K). Here we present two conceptually new and intriguing approaches to enhance substitutional doping of Mn in Ge and Si, based on first-principles calculations. One is via subsurfactant epitaxy, the other is via n-p co-doping. In the former case, the resultant materials exhibit homogeneous distributions of substitutional Mn dopants with Tc>300K, as observed experimentally. In the latter case, we find that co-doping faciliates the efficiency of Mn substitutional occupation, and observe dramatically enhanced anisotropy in the ferromagnetic coupling between the dopants. These results will be compared in connection with the recent developments of the field emphasizing the importance of nano-columns within the DMS.

*Work done in collaboration with Wenguang Zhu, Hanno Weitering, Changgan Zeng, Enge Wang, Tim Kaxiras, Mina Yoon, Klaus van Benthem, and Matthew Chrisholm. Supported by US. NSF (Grant No. DMR-0606485), the NSF of China, and by the Division of Materials Sciences and Engineering, Office of Basic Energy Sciences, US Department of Energy, under contract DE-AC05-00OR22725 with ORNL, managed and operated by UT-Battelle, LLC.