Abstract
This chapter discusses the recent observations of the impact of surface effects on the optical properties of GaN-based NWs. It focuses on three aspects: (1) the existence of specific exciton and donor quantum states related to surfaces; (2) the intrinsic non-radiative activity of surfaces; (3) the impact on electron-hole pair recombination dynamics of the physical and chemical environment of the NWs. The non-radiative recombination at the surface of nitride NWs is generally believed to occur and that the band bending resulting from the pinning of Fermi level on surface states is generally believed to control access of carriers to those surface states, whereas it would also efficiently separate photo-generated electrons and holes. In particular, holes are believed to be driven toward the surface. The photochemical activity of this surface, most certainly related to photocarrier transport from and toward surface states, has strong effects on the optical properties of the NWs.