  Diluted magnetic semiconductors (DMSs) based on group-IV materials are
desirable for spintronic devices compatible with current silicon technology. In
this work, amorphous Mn-doped SiGe thin films were first fabricated on Ge
substrates by radio frequency magnetron sputtering and then crystallized by
rapid thermal annealing (RTA). After the RTA, the samples became ferromagnetic
(FM) semiconductors, in which the Curie temperature increased with increasing
Mn doping concentration and reached 280 K with 5% Mn concentration. The data
suggest that the ferromagnetism came from the hole-mediated process and was
enhanced by the tensile strain in the SiGe crystals. Meanwhile, the Hall effect
measurement up to 33 T to eliminate the influence of anomalous Hall effect
(AHE) reveals that the hole mobility of the annealed samples was greatly
enhanced and the maximal value was ~1000 cm2/Vs, owing to the tensile
strain-induced band structure modulation. The Mn-doped SiGe thin films with
high Curie temperature ferromagnetism and high hole mobility may provide a
promising platform for semiconductor spintronics.
