Origin of the Novel Magnetoresistance Oscillation of the Two-Dimensional Electron Gas in Al_xGa_1-xN/GaN Heterostructures

In the magnetotransport measurements of the two-dimensional electron gas (2DEG) in modulation-doped Al_0.22Ga_0.78N/GaN heterostructures, a new magnetoresistance oscillation of the 2DEG is observed at low magnetic fields when the Al_0.22Ga_0.78N layer on GaN is under partially relaxed. It is thought that the misfit dislocations induced by the partialy relaxed Al_0.22Ga_0.78N layer modulate the distribution of the piezoelectric polarization-induced charges at the Al_0.22Ga_0.78N/GaN heterointerface, and thus produce a strong modulation-potential at the heterointerface. The strong modulation-potential results in the novel magnetoresistance oscillation of the 2DEG at low magnetic fields.