  One of the main limiting factors in the carrier mobility in semiconductor
nanowires is the presence of deep trap levels. While deep-level transient
spectroscopy (DLTS) has proved to be a powerful tool in analysing traps in bulk
semiconductors, this technique is ineffective for the characterisation of
nanowires due to their very small capacitance. Here we introduce a new
technique for measuring the spectrum of deep traps in nanowires. In
current-mode DLTS (I-DLTS) the temperature-dependence of the transient current
through a nanowire field-effect transistor in response to an applied gate
voltage pulse is measured. We demonstrate the applicability of I-DLTS to
determine the activation energy and capture cross-sections of several deep
defect states in zinc oxide nanowires. In addition to characterising deep
defect states, we show that I-DLTS can be used to measure the surface barrier
height in semiconductor nanowires.
