Spin splitting in modulation-doped AlxGa1-xN/GaN heterostructures

We have studied the electronic properties of Al x Ga 1 - x N/GaN heterostructures by using Shubnikov-de Haas (SdH) measurement. Two SdH oscillations were detected on the samples of x=0.35 and 0.31, due to the population of the first two subbands with the energy separations of 128 and 109 meV, respectively. For the sample of x=0.25, two SdH oscillations beat each other, probably due to a finite zero-field spin splitting. The spin-splitting energy is equal to 9.0 meV. The samples also showed a persistent photoconductivity effect after illuminating by blue light-emitting diode.