Nano Lett. 2019 Mar 13;19(3):1814-1820. doi: 10.1021/acs.nanolett.8b04869. Epub 2019 Feb 26.
We have achieved heteroepitaxial stacking of a van der Waals ( vdW) monolayer metal, 1T'-WTe, and a semiconductor, 2H-WSe, in which a distinctively low contact barrier was established across a clean epitaxial vdW gap. Our epitaxial 1T'-WTe films were identified as a semimetal by low temperature transport and showed the robust breakdown current density of 5.0 × 10 A/cm. In comparison with a series of planar metal contacts, our epitaxial vdW contact was identified to possess intrinsic Schottky barrier heights below 100 meV for both electron and hole injections, contributing to superior ambipolar field-effect transistor (FET) characteristics, i.e., higher FET mobilities and higher on-off current ratios at smaller threshold gate voltages. We discuss our observations around the critical roles of the epitaxial vdW heterointerfaces, such as incommensurate stacking sequences and absence of extrinsic interfacial defects that are inaccessible by other contact methods.
我们实现了范德华（vdW）单层金属 1T'-WTe 和半导体 2H-WSe 的异质外延堆叠，在清洁的外延 vdW 间隙中建立了明显的低接触势垒。我们的外延 1T'-WTe 薄膜通过低温输运被确定为半导体，并表现出稳健的击穿电流密度 5.0×10^4 A/cm。与一系列平面金属接触相比，我们的外延 vdW 接触被确定为具有低于 100 meV 的本征肖特基势垒高度，用于电子和空穴注入，这有助于实现优越的双极型场效应晶体管（FET）特性，即更小的阈值栅极电压下更高的 FET 迁移率和更高的导通-关断电流比。我们讨论了围绕外延 vdW 异质界面的关键作用的观察结果，例如失配堆叠序列和不存在其他接触方法无法获得的外在界面缺陷。
