Large Bychkov-Rashba spin-orbit coupling in high-mobility GaN/AlxGa1-xN heterostructures

We present low-temperature magnetoconductivity measurements of a density-tunable and high mobility two-dimensional electron gas confined in the wide band-gap GaN/AlGaN system. We observed pronounced antilocalization 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)similar to 6x10(-13) eV m, while the conduction-band spin-orbit splitting energy amounts to Delta(so)similar to 0.3 meV at n(e)=1x10(16) m(-2).