Strong confinement-induced engineering of the g factor and lifetime of conduction electron spins in Ge quantum wells

• Published in: Nature communications 2016-12, Vol.7 (1), p.13886-13886, Article 13886
• Main Authors: Giorgioni, Anna, Paleari, Stefano, Cecchi, Stefano, Vitiello, Elisa, Grilli, Emanuele, Isella, Giovanni, Jantsch, Wolfgang, Fanciulli, Marco, Pezzoli, Fabio
• Format: Article
• Language: English
• Subjects: 140/125; 639/301/119/1000; 639/301/119/1001; Charged particles; Electrons; Humanities and Social Sciences; Lifetime; multidisciplinary; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms13886

Control of electron spin coherence via external fields is fundamental in spintronics. Its implementation demands a host material that accommodates the desirable but contrasting requirements of spin robustness against relaxation mechanisms and sizeable coupling between spin and orbital motion of the carriers. Here, we focus on Ge, which is a prominent candidate for shuttling spin quantum bits into the mainstream Si electronics. So far, however, the intrinsic spin-dependent phenomena of free electrons in conventional Ge/Si heterojunctions have proved to be elusive because of epitaxy constraints and an unfavourable band alignment. We overcome these fundamental limitations by investigating a two-dimensional electron gas in quantum wells of pure Ge grown on Si. These epitaxial systems demonstrate exceptionally long spin lifetimes. In particular, by fine-tuning quantum confinement we demonstrate that the electron Landé g factor can be engineered in our CMOS-compatible architecture over a range previously inaccessible for Si spintronics. Ge/Si heterojunctions are prominent candidates for spintronics, but the spin-dependent phenomena have been elusive. Here, Giorgioni et al . report long spin relaxation and coherence times in a two dimensional electron gas confined in quantum wells of pure Ge grown on SiGe-buffered Si substrates.