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The in-plane anisotropy of the effective g factors in Al0.25Ga0.75N/GaN based quantum point contacts with narrow channels

The effective g factors (g*) of the lowest three subbands of Al0.25Ga0.75N/GaN-based quantum point contacts (QPCs) are obtained in various magnetic field orientations. The g factors show an anisotropic enhancement compared to those in the two-dimensional electron gas, among which an in-plane anisotropy becomes manifested, when the QPC is depleted from the third to the first subband and the channel width shrinks from the order of 10−7 m–10−8 m. In the one-dimensional (1D) regime with only one subband in the QPC, the in-plane g* perpendicular to the current is evidently larger than the parallel one. The in-plane anisotropy can be attributed to the Rashba spin–orbit coupling (SOC) in the narrow confinement. The reason that the anisotropy can be observed in this work, but not in conventional III–V semiconductors studied previously, is due to the fact that the Al0.25Ga0.75N/GaN-based QPCs have larger polarization-field-induced Rashba SOC and much stronger 1D constriction.