Electrostatic Modulation of the Electronic Properties of Dirac Semimetal Na3Bi

Large-area thin films of topological Dirac semimetal Na${}_3$Bi are grown on amorphous SiO${}_2$:Si substrates to realise a field-effect transistor with the doped Si acting as back gate. As-grown films show charge carrier mobilities exceeding 7,000 cm${}^2$/Vs and carrier densities below 3 $\times$10${}^{18}$ cm${}^{-3}$, comparable to the best thin-film Na${}_3$Bi. An ambipolar field effect and minimum conductivity are observed, characteristic of Dirac electronic systems. The results are quantitatively understood within a model of disorder-induced charge inhomogeneity in topological Dirac semimetals. Due to the inverted band structure, the hole mobility is significantly larger than the electron mobility in Na${}_3$Bi, and when present, these holes dominate the transport properties.