Modulating Electrical Properties of InAs Nanowires via Molecular Monolayers

In recent years, InAs nanowires have been demonstrated with the excellent electron mobility as well as highly efficient near-infrared and visible photoresponse at room temperature. However, due to the presence of a large amount of surface states that originate from the unstable native oxide, the fabricated nanowire transistors are always operated in the depletion mode with degraded electron mobility, which is not energy-efficient. In this work, instead of the conventional inorganic sulfur or alkanethiol surface passivation, we employ aromatic thiolate (ArS^-)-based molecular monolayers with controllable molecular design and electron density for the surface modification of InAs nanowires (i.e., device channels) by simple wet chemistry. More importantly, besides reliably improving the device performances by enhancing the electron mobility and the current on-off ratio through surface state passivation, the device threshold voltage (V_Th) can also be modulated by varying the para-substituent of the monolayers such that the molecule bearing electron-withdrawing groups would significantly shift the V_Th towards the positive region for the enhancement mode device operation, in which the effect has been quantified by density functional theory calculations. These findings reveal explicitly the efficient modulation of the InAs nanowires' electronic transport properties via ArS^--based molecular monolayers, which further elucidates the technological potency of this ArS^- surface treatment for future nanoelectronic device fabrication and circuit integration.