  We report evolution of the two-dimensional electron gas behavior at the
NdAlO3/SrTiO3 heterointerfaces with varying thicknesses of the NdAlO3
overlayer. The samples with a thicker NdAlO3 show strong localizations at low
temperatures and the degree of localization is found to increase with the
NdAlO3 thickness. The T -1/3 temperature dependence of the sheet resistance at
low temperatures and the magnetoresistance study reveal that the conduction is
governed by a two-dimensional variable range hopping mechanism in this strong
localized regime. We attribute this thickness dependence of the transport
properties of the NdAlO3/SrTiO3 interfaces to the interface strain induced by
the overlayers.
