Drift velocity saturation in field-effect transistors based on single CdSe nanowires

Field-effect transistors (FETs) based on semiconductor nanowires (NWs) have been extensively investigated and used for constructing novel nanoelectronic and optoelectronic devices in the past two decades. High electric field transport characteristics in FETs are of significance in both physics and applications. However, some specific physics phenomena at high electric field, such as drift velocity saturation, have rarely been reported in semiconductor NW FETs. In this work, the high electric field transport characteristics in FETs based on CdSe NWs were investigated. In the output characteristic curves, the current saturation phenomenon at high electric field caused by drift velocity saturation was observed. Typical values of saturation drift velocity and low electric field mobility in CdSe NW FETs were obtained. The low electric field mobility is in the range of 265.2 to 388.0 cm² V^-1 s^-1. The saturation drift velocity is in the range of 5.1 × 10⁵ to 7.0 × 10⁵ cm s^-1 and decreases monotonically with the increase of charge density, indicating that the electron-phonon scattering mechanism dominates at high electric field. Saturation drift velocity is an important figure-of-merit which characterizes the high electric field transport performance in FETs. As far as we know, this is the first experimental report on saturation drift velocity in CdSe NW FETs, which may provide valuable guidance for the design of nanoelectronic and optoelectronic devices based on CdSe NWs in the future.