Magnetotransport of metal-oxide-semiconductor devices fabricated on highly enriched ²⁸Si

Isotopically enriched ²⁸Si is regarded as an ideal environment for quantum computation (QC) as elimination of unpaired nuclear spins can result in low error rates for QC. At NIST we have developed a method to grow isotopically enriched ²⁸Si, which provides the unique advantage of targeting a desired enrichment anywhere between natural abundance and the highest possible enrichment > 99.99998 % ²⁸Si isotopic fractions. To explore the electrical properties of ²⁸Si, we fabricate gated Hall bar devices and study the magnetotransport at magnetic fields (B) 12 T and temperatures (T) ranging from 1.2 K to 10 K. The magnetoresistance at |B| ≤ 0.25 T shows maximum mobilities of ≈ 1700 cm²/(V×s) and ≈ 6000 cm²/(V×s) at an electron density of ≈ 2.5×10¹² cm^-2 for devices fabricated on ²⁸Si and ^nat.Si, respectively. We use the T dependence of weak-localization and Shubnikov-de Haas oscillations to deduce the dominant scattering mechanisms in these devices. We believe that the lower mobility observed for the devices fabricated on ²⁸Si is due to the dilute adventitious C, N and O detected in ²⁸Si. We will also discuss the preliminary results of fabrication and measurement of gate defined quantum dot devices in ²⁸Si epilayers.