The effects of thicknesses, alloy fraction and doping density of different layers in a novel pseudomorphic n-GaN/InxAl1-xN/AlN/GaN ultrathin barrier heterostructures on band structures and carrier densities were investigated with the help of one-dimensional self-consistent solutions of non-linear Schrodinger-Poisson equations. The calculations include polarization-induced carriers and thermally activated bulk carriers. Important increments in carrier density are found with increasing thickness and decreasing indium-mole fraction of In,All NI ultrathin barrier layer. From an experimental point of view, two different device structures are suggested for the low-bias and high-bias applications. (C) 2010 Elsevier B.V. All rights reserved.