Measurements of Shubnikov-de Haas effect in highly enriched ²⁸Si Hall bars

Elimination of unpaired nuclear spins can improve the fidelity of the quantum information; therefore, isotopically enriched ²⁸Si is regarded as an ideal environment for quantum information processing devices. Using mass selected ion beam deposition technique, we in-situ enrich and deposit epitaxial ²⁸Si and routinely achieving better than 99.99998 % ²⁸Si isotope fractions. To explore the electrical properties and optimize the growth conditions of in-situ enriched ²⁸Si, we fabricate top gated Hall bar devices, and investigate the magnetotransport in this material at magnetic fields as high as 12 T and temperature ranging from 20 K to 1.2 K. The data at low magnetic fields [endif]--> shows maximum mobilities of approximately 2500 cm²/Vs and 5000 cm²/Vs at an electron density of ≈ 2.5 x 10¹² cm^-2 for devices fabricated on ²⁸Si and natural Si, respectively. Temperature dependence of Shubnikov-de Hass oscillations in longitudinal magnetoresistance (R_xx) at B > 2 T is used to extract the effective mass for charge carriers. Here, we report on the above device metrics, and compare to similar devices fabricated on natural Si.