Temperature Dependence of Electron Transport in ZnO Nanowire Field Effect Transistors

Nanowires (NWs) have attracted considerable interests for electronic and optoelectronic device applications. However, the carrier transport mechanisms in these NW devices have not been well understood. Here we present the electron transport of ZnO NWs field effect transistors (FETs). Our results show that the electron transport of ZnO NW FETs is governed by the space charge limited model at temperatures below a trap temperature. Above the trap temperature, the electron transport is thermionic emission dominated. Based on the space charge limited model, an accurate method is developed for field effect mobility extraction. The extracted electron carrier mobility is strongly dependent on temperature with a peak value of 51 cm²/Vs at 167 K. Under the space-charge limited transport, the field mobility is lower in comparison with the values extracted from the thermionic emission model. The electron mobility due to space charge scattering has a value of 483 cm²/Vs at the trap temperature with temperature dependence of T^{4 ~ 5}. The interface state density between the back gate dielectric and ZnO NWs is in the range 9.03×10⁶/cm-8.72×10⁷/cm at temperatures ranging from 77 to 227 K.