Exchange-enhanced g-factors in an Al0.25Ga0.75N/GaN two-dimensional electron system

Low-temperature magnetotransport measurements were performed on an Al0.25Ga0.75N/GaN two-dimensional electron system. In this system, we observe Shubnikov-de Haas (SdH) oscillations in a perpendicular magnetic field B. By measuring the positions of a pair of spin-split SdH maxima, we are able to estimate the g-factors at different Landau level (LL) indices. We find the g-factor is enhanced over its bulk value in GaN (congruent to2) due to many-body exchange interactions. Moreover, the measured g-factor increases with decreasing LL index, indicating that many-body electron-electron interactions become stronger as the number of occupied LLs decreases. Our results suggest that the exchange energy E-ex shows an approximately linear B dependence. (C) 2004 American Institute of Physics.