Al<sub>0.75</sub>Ga<sub>0.25</sub>N/Al<sub>x</sub>Ga<sub>1-x</sub>N/Al<sub>0.75</sub>Ga<sub>0.25</sub>N/AlN/SiC Metal–Oxide–Semiconductor Heterostructure Field-Effect Transistors With Symmetrically-Graded Widegap Channel
IEEE journal of the Electron Devices Society