High-Field Electron Transport and High Saturation Velocity in Multilayer Indium Selenide Transistors.

Creating a high-frequency electron system demands a high saturation velocity (υ sat ). Herein, we report the high-field transport properties of multilayer van der Waals (vdW) indium selenide (InSe). The InSe is on a hexagonal boron nitride substrate and encapsulated by a thin, noncontinuous In layer, resulting in an impressive electron mobility reaching 2600 cm 2 /(V s) at room temperature. The high-mobility InSe achieves υ sat exceeding 2 × 10 7 cm/s, which is superior to those of other gapped vdW semiconductors, and exhibits a 50-60% improvement in υ sat when cooled to 80 K. The temperature dependence of υ sat suggests an optical phonon energy ( ℏ ω op ) for InSe in the range of 23-27 meV, previously reported values for InSe. It is also notable that the measured υ sat values exceed what is expected according to the optical phonon emission model due to weak electron-phonon scattering. The superior υ sat of our InSe, despite its relatively small ℏ ω op , reveals its potential for high-frequency electronics, including applications to control cryogenic quantum computers in close proximity.