University
of North Carolina - Chapel Hill
control both electronic and magnetic properties of semiconductors by
doping them with magnetic dopants. The challenge is how to
stabilize relatively high doping levels required for
achieving high temperature ferromagnetism without destroying
the semiconductor. Doping with a single element beyond
several percent not only induces epitaxial strain, but also promotes
phase separation and metallic behavior, thus making
epitaxial growth unstable. In this talk we describe the MBE
synthesis and characterization of promising new Ge-based
magnetic semiconductors and heterostructures. We highlight key
findings in the epitaxial phase diagram, and the novel magnetic and
transport phenomena. We show that the use of two dopants with
appropriate relative concentrations a range of desirable
'compensation' effects can be achieved, including
compensation of strain and carrier effects caused by the
individual dopants, thus stabilizing epitaxial growth and
semiconductivity at higher doping levels. Applying this approach to
other multi-dopant systems opens new avenues for tailoring
highly doped electronic materials.