Random telegraph signals in n-type ZnO nanowire field effect transistors at low temperature

Single-crystal zinc oxide (ZnO) nanowires have been fabricated as field effect transistors (FETs). The characteristics of low frequency noise in the drain current of n-type ZnO FETs have been investigated through random telegraph signals (RTSs) at 4.2K. At room temperature, the noise power spectra have a classic 1∕f dependence with a Hooge parameter that is ∼5×10−3. At 4.2K, the device’s noise spectra change from 1∕f to Lorentzian type, and the current traces as a function of time show RTSs. The channel current RTSs are attributed to correlated carrier number and mobility fluctuation due to the trapping and emission of carriers by discrete border traps. At certain bias conditions, the current in the channel shows three-level switching events with amplitudes as high as 40%, from which two individual defects with energies close to the Fermi level in the ZnO channel can be distinguished.