  Excitons hosted by GaN/(Al,Ga)N quantum wells (QWs) are spatially indirect
due to the giant built-in electric field that separates electrons and holes
along the growth direction. This electric field, and thus exciton energy, can
be reduced by depositing metallic layers on the sample surface. Using
spatially-resolved micro-photoluminescence spectroscopy we compare the effects
of two different materials, Nickel/Gold (NiAu) and few-layered graphene (FLG),
on the potential landscape experienced by the excitons. We are able to (i)
determine the potential barriers imposed on QW excitons by deposition of FLG
and NiAu to be $14$ and $82$~meV, respectively, and (ii) to evidence their
impact on the exciton transport at appropriate densities. Optical losses and
inhomogeneous broadening induced by deposition of NiAu and FLG layers are
similar, and their joined implementation constitute a promising tool for
electrostatic modulation of IX densities even in the absence of any applied
electric bias.
