Three Subband Occupation of the Two‐Dimensional Electron Gas in Ultrathin Barrier AlN/GaN Heterostructures

Ultrathin barrier AlN/GaN heterostructure with record low sheet resistance of 82 Ω sq −1 is achieved by molecular beam epitaxy, where Shubnikov‐de Haas oscillations (SdHOs) and quantum Hall effect (QHE) of two‐dimensional electron gas (2DEG) are observed. The fast Fourier transform analysis of the SdHOs demonstrates a three‐subband occupation in the triangle quantum well for the first time, with the electron density of n 1 = 2.2 × 10 13 cm −2 ,...