Presentation Information
[8p-E207-14]Epitaxial Growth and Properties of High-mobility Topological Dirac Semimetal α-Sn Thin Films on Semi-insulating GaAs (001) Substrates
〇Harunori Shiratani1, Le Duc Anh1,2, Masaaki Tanaka1,2 (1.Univ. of Tokyo, 2.CSRN Univ. of Tokyo)
Keywords:
topological Dirac semimetal
α-Sn is a tin allotrope with a diamond-type crystal structure. Owing to its inverted band structure, α-Sn can host various topological phases, including topological insulator (TI) and topological Dirac semimetal (TDS) phases, which can be controlled by film thickness and epitaxial strain. Thus far, α-Sn thin films have been grown typically on lattice-matched zinc-blende-type semiconductor substrates such as InSb and CdTe. However, the narrow bandgap of InSb causes parallel conduction, making it difficult to characterize the intrinsic electrical transport properties of α-Sn. CdTe is another suitable substrate because of its wider bandgap and superior insulating properties; however, it is relatively expensive and available only in limited wafer diameters. Therefore, establishing a method for growing high-quality α-Sn thin films on large-diameter, low-cost insulating substrates is essential for both understanding the intrinsic physics of α-Sn and developing α-Sn-based device applications. We grew α-Sn/(In,Al)Sb/GaAs heterostructures on semi-insulating GaAs(001) substrates by molecular beam epitaxy. The layer structure consisted of an α-Sn (65 or 40 nm) layer grown on a 310 nm-thick (In0.916,Al0.084)Sb buffer layer. Shubnikov–de Haas (SdH) oscillations were observed in both the 65-nm-thick and 40-nm-thick α-Sn films. For the 65-nm-thick α-Sn film, a dominant fast Fourier transform (FFT) peak was seen at 17 T, corresponding to a carrier concentration of 4.2×1011 cm-2. The Fermi surface exhibits two-dimensional behavior, and the effective mass, mobility, and Berry phase were estimated to be 0.04 m0, 9050 cm2 V-1 s-1, and 0.36, respectively (m0 is the free-electron mass). These results suggest that the observed SdH oscillations originate from a high-mobility, topologically nontrivial transport channel of the α-Sn layer.