Formation of two-dimensional electron gas at AlGaN/GaN heterostructure and the derivation of its sheet density expression*
He Xiao-Guang, Zhao De-Gang†, Jiang De-Sheng
       
Energy band of n-doped freestanding AlGaN film (assuming the AlGaN layer to be under the same tensile strain as that when growing on GaN). Conductive electrons move under the polarization-induced electric field from one side to the other, thereby bending the energy band, and leaving fixed positive charges in the AlGaN layer.