Demonstration of large field effect in topological insulator films via a high-κ back gate
Journal
Applied Physics Letters
Journal Volume
108
Journal Issue
20
Date Issued
2016
Author(s)
Wang C.Y
Lin H.Y
Yang S.R
Chen K.H.M
Lin Y.H
Chen K.H
Young L.B
Fanchiang Y.T
Tseng S.C
Hong M
Kwo J.
Abstract
The spintronics applications long anticipated for topological insulators (TIs) has been hampered due to the presence of high density intrinsic defects in the bulk states. In this work we demonstrate the back-gating effect on TIs by integrating Bi2Se3 films 6-10 quintuple layer (QL) thick with amorphous high-κ oxides of Al2O3 and Y2O3. Large gating effect of tuning the Fermi level EF to very close to the band gap was observed, with an applied bias of an order of magnitude smaller than those of the SiO2 back gate, and the modulation of film resistance can reach as high as 1200%. The dependence of the gating effect on the TI film thickness was investigated, and ΔN2 D/ΔVg varies with TI film thickness as ∼t-0.75. To enhance the gating effect, a Y2O3 layer thickness 4 nm was inserted into Al2O3 gate stack to increase the total κ value to 13.2. A 1.4 times stronger gating effect is observed, and the increment of induced carrier numbers is in good agreement with additional charges accumulated in the higher κ oxides. Moreover, we have reduced the intrinsic carrier concentration in the TI film by doping Te to Bi2Se3 to form Bi2TexSe1 - x. The observation of a mixed state of ambipolar field that both electrons and holes are present indicates that we have tuned the EF very close to the Dirac Point. These results have demonstrated that our capability of gating TIs with high-κ back gate to pave the way to spin devices of tunable EF for dissipationless spintronics based on well-established semiconductor technology. © 2016 Author(s).
Other Subjects
Alumina; Aluminum oxide; Amorphous films; Carrier concentration; Electric insulators; Energy gap; Film thickness; Selenium compounds; Semiconductor device manufacture; Semiconductor devices; Semiconductor doping; Silica; Ambipolar field; Carrier numbers; Electrons and holes; Film resistance; Intrinsic defects; Semiconductor technology; Spintronics application; Topological insulators; Bismuth compounds
Type
journal article