Two-subband-populated AlGaN∕GaN heterostructures probed by electrically detected and microwave-modulated magnetotransport measurements

The authors apply the microwave-modulated technique to study the transport properties of two-subband-populated AlGaN∕GaN heterostructures. The microwave modulation enhances the small Shubnikov–de Haas oscillations at low magnetic fields, providing a direct way to compare the mobilities of different subbands from the experimental data. In addition, this technique can help us to determine the subband-energy separation, especially when the population of the second subband is much lower than that of the first one. Variation of subband-energy separation due to different spacer thicknesses is obtained. Therefore, the authors showed a powerful way to probe parameters of two-subband-populated AlGaN∕GaN heterostructures.