Large Bychkov-Rashba spin-orbit coupling in high mobility wide bandgap GaN/AlGaN heterostructures

We present low temperature magnetoconductivity measurements of a density-tunable and high mobility two-dimensional electron gas confined in the wide bandgap GaN/AlGaN system. We observed pronounced anti-localization minima in the low-field conductivity, indicating the presence of strong spin-orbit coupling. Density dependent measurements of magnetoconductivity indicate that the coupling is mainly due to the Bychkov-Rashba mechanism. In addition, we have derived a closed-form expression for the magnetoconductivity, allowing us to extract reliable transport parameters for our devices. The Rashba spin-orbit coupling constant is $alpha_{so}$ $sim$ 6$times$ 10$^{-13}$eVm, while the conduction band spin-orbit splitting energy amounts to $Delta_{so}$ $sim$ 0.3meV at n$_e$=1$times$10$^{16}$m$^{-2}$.