a1 Paul-Drude-Institut für Festkörperelektronik, 10117 Berlin, Germany
a2 Peter Grünberg Institut (PGI-9), Forschungszentrum Jülich, D-52425 Jülich, Germany; and Jülich-Aachen Research Alliance, D-52425 Jülich, Germany
a3 Paul-Drude-Institut für Festkörperelektronik, 10117 Berlin, Germany
Semiconductor nanowires (NWs) are characterized by an extraordinarily large surface-to-volume ratio. Consequently, surface effects are expected to play a much larger role than in thin films. Here, we review a research focused on the impact of the surface on the electrical and optical properties of catalyst-free GaN NWs with growth direction <0001>. Using a combination of complementary experimental techniques, it has been shown that the Fermi level is pinned at the NW sidewall surfaces, resulting in internal electric fields and in full depletion for NWs below a critical diameter. Deoxidation of the surfaces unpins the Fermi level, leading to enhanced radiative recombination of excitons. Prominent absorption below the bandgap is caused by the Franz-Keldysh effect. Close to the surface, the ionization energy of donors is reduced. The consideration of surface-induced effects is mandatory for an understanding of the physical properties of NWs as well as their application in devices.
(Received June 10 2011)
(Accepted June 16 2011)
This section of Journal of Materials Research is reserved for papers that are reviews of literature in a given area.