Improving the electrical properties of InAs nanowire field effect transistors by covering them with YO/HfO layers.

Quasi-one-dimensional semiconducting materials have attracted increasing attention due to their excellent ability to downscale the size of transistors. However, in quasi-one-dimensional nanowire (NW) transistors, their surface and interface properties play a very important role mainly due to the large surface-to-volume ratio of NWs and surface scattering, which degrade their carrier mobility. Herein, we developed a new method to cover the channel surface of InAs NW field effect transistors (FETs) with YO/HfO layers to improve their electrical properties. We successfully fabricated nine FETs and measured their electrical properties, which improve after depositing the YO/HfO layers, including an increase in on-state current, decrease in off-state current, increase in transconductance, increase in electron mobility and decrease in subthreshold swing. By comparing the properties of YO/HfO-covered devices with that of the FETs fabricated without the YO covering or without annealing, we prove that it is the combined YO/HfO layers instead of only the YO or HfO layer that improve the electrical properties of the FETs. The Cs-corrected high-resolution scanning transmission electron microscopy study demonstrates that Y can actually diffuse through the native oxide layer (confirmed to be InO) and reach the surface of the InAs NWs. Our results indicate that the desirable characteristics of YO and the surface passivation by HfO improve the electrical properties of the InAs NW FETs, in which YO plays an important role to modify and stabilize the interface between the InAs NWs and the outside dielectric layer. Furthermore, this method should also be applicable to other III-V materials.