J. Rojas-Trigos, M. López-López, M. Venegas, G. Contreras-Puente, D. Jiménez-Olarte, and G. Santana-Rodríguez, Electrical characterization of GaN/ALN heterostructures grown by molecular beam epitaxy on silicon substrates, Rev. Mex. Fís. 62, (2016).