(a) Lateral constriction in a semiconductor nanocolumn.
(b) Transport model with non-uniform lateral subbands.
At a first glance, Fermi-level pinning and the resulting surface depletion of many III-V semiconductor materials might have a negative impact on the scaling properties of semiconductor nanodevices. However, considering a nanocolumn with embedded double-barrier energy filter, we have demonstrated how one can actually utilize a non-uniform surface depletion region for the realization of a quantum constriction within the channel of the nanocolumn [1,2]. Due to the resulting few-mode transport scenario, an improved nanodevice performance can be predicted from a simple quantum collimation model (see figure). Indeed, such a behavior has been observed experimentally in our GaAs-based top-down nanocolumn devices [1,3].
 Nano Letters 5, 2470-2475 (2005)
 Appl. Phys. A 87, 559 (2007)
 Nanotechnology 20, 465402 (2009)