SEMICONDUCTOR SPINTRONICS
High Curie temperature ferromagnetism and high hole mobility in tensile strained Mn-doped SiGe thin films
Adv. Funct. Mater., 2002513 (2020)
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Up to now, substantial work has been carried out on different materials-based diluted magnetic semiconductors, and great achievements have been made on increasing Curie temperature of these materials. However, the carrier mobility of the magnetic semiconductors is still low due to various scatterings, and rare studies have been performed to effectively enhance the carrier mobility. As we know, both high Curie-temperature ferromagnetism and high carrier mobility are important characteristics for ideal magnetic semiconductors, which are essential for spin polarized current generation and transport in real spintronic semiconducting devices.
Recently, the research team led by Prof. Gang Xiang from Sichuan University, China has demonstrated a way for enhancing both ferromagnetism and carrier mobility in group-IV thin films compatible with current silicon technology. Specifically, Mn-doped SiGe thin films were first fabricated on Ge substrates by radio frequency magnetron sputtering and then crystallized by rapid thermal annealing. After annealing, the samples became ferromagnetic, in which the Curie temperature increases with increasing Mn doping concentration and reaches 280 K with 5% Mn concentration. The data suggest that the ferromagnetism comes from the hole-mediated process and is enhanced by the tensile strain in the SiGe crystals. In addition, the Hall effect measurement up to 33 T to eliminate the influence of anomalous Hall effect reveals that the hole mobility of the annealed samples is greatly enhanced and the maximal value is ~1000 cm2·V–1·s–1, 2 orders of magnitude bigger than other magnetic semiconductors, owing to the tensile strain-induced separation of heavy holes and light holes on the valence band top. As a result, the tensile-strained Mn-doped SiGe thin films exhibit both high Curie-temperature ferromagnetism and high hole mobility, which is one piece of few exciting news since the outbreak of COVID-19 epidemic, especially for the community of semiconductor spintronics.
Jianhua Zhao (State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, China)
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