A method of growing a III-nitride-based epitaxial structure is disclosed. The method includes forming a GaN-based drift layer coupled to the GaN-based substrate, where forming the GaN-based drift layer comprises doping the drift layer with indium to cause the indium concentration of the drift layer to be less than about 1×1016 cm−3 and to cause the carbon concentration of the drift layer to be less than about 1×1016 cm−3. The method also includes forming an n-type channel layer coupled to the GaN-based drift layer, forming an n-contact layer coupled to the GaN-based drift layer, and forming a second electrical contact electrically coupled to the n-contact layer.