Enhanced anisotropic effective g factors of an Al0.25Ga 0.75N/GaN heterostructure based quantum point contact

Gate-defined quantum point contacts (QPCs) were fabricated with Al0.25Ga0.75N/GaN heterostructures grown by metal organic chemical Vapor deposition (MOCVD). In the transport study of the Zeeman effect, greatly enhanced effective g factors (g*).were obtained. The in-plane g* is found to be 5.5 +/- 0.6, 4.8 0.4, and 4.2 0.4 for the first to the third subband, respectively. Similarly, the out-of-plane g* is 8.3 0.6, 6.7 0.7, and 5.1 0.7. Increasing g* with the population of odd-numbered spin-splitted subbands are obtabed at 14 T. This portion of increase is assumed to arise from the exchange interaction in one-dimensional systems. A careful analysis shows that not only the exchange interaction but the spin orbit interaction (SOI) in the strongly confined QPC contribunts to the enhancement and anisotropy of g* in different subbands. An approach to distinguish the respective contributions from the SOI and exchange interaction is therefore proposed.