Scanning Capacitance Characterization of Potential Screening in InAs Nanowire Devices

We have used scanning capacitance microscopy (SCM) and spectroscopy (SCS) to examine the effects of micron- scale metal contacts, typically present in nanowire-based electronic devices, on carrier modulation and electrostatic behavior in InAs semiconductor nanowires. We observe a pronounced dependence of scanning capacitance images and spectra on distance between the scanning capacitance probe tip and nanowire contact up to distances of 3-4 mum. Based on comparison of these data with results of finite-element electromagnetic simulations, we interpret these results as a consequence of electrostatic screening of the tip-nanowire potential difference by the large metal contact. The results provide direct experimental verification of contact screening effects predicted in the literature, and are expected to have substantial implications for the design and expected performance of nanowire-based electronic devices, most notably nanowire field-effect transistors. Ultimately, they are indicative of the importance of assessing and accounting for the effect of large- scale contact and circuit elements on the characteristics of nanoscale electronic devices.