Abstract: Various exemplary embodiments of the devices and methods for this invention provide for a semiconductor structure and a method of manufacturing a semiconductor structure that includes providing an aluminum nitride nucleation layer over a substrate, providing an undoped AlGaN buffer layer over the aluminum nitride nucleation layer, providing an undoped GaN over the AlGaN buffer layer, providing a plurality of AlGaN layers over the GaN layer wherein the plurality of aluminum GaN layers comprise a first layer provided over the undoped GaN layer, a second layer provided over the first layer and the third layer provided over the second layer, providing a source electrode and a drain electrode, through the first, second and third aluminum gallium nitride layers, the source electrode and the drain electrode being in electrical contact with the gallium nitride layer and providing a gate electrode over the third aluminum gallium nitride layer.