Detailed band alignment of high-B-composition BGaN with GaN and AlN

The electronic structure of B0.097Ga0.903N was determined by examining its bandgap and valence band offset (VBO) in detail. The BGaN sample was grown using a horizontal reactor metalorganic chemical vapor deposition. For bandgap determination, three different techniques were utilized yielding similar results, which are: UV-Vis spectroscopy, Schottky photodiodes, and electron energy-loss spectroscopy. The bandgap was determined to be ~3.55 eV. For measuring the VBO, the valence edges and the core levels of Al 2s and Ga 2p were measured using x-ray photoelectron spectroscopy (XPS). The valence edges were then fitted and processed along with the core levels using the standard Kraut method for VBO determination with AlN. The BGaN/AlN alignment was found to be -1.1 ± 0.1 eV. Due to core level interference between GaN and BGaN, the Kraut method fails to provide precise VBO for this heterojunction. Therefore, a different technique is devised to analyze the measured XPS data which utilizes the alignment of the Fermi levels of the BGaN and GaN layers when in contact. Statistical analysis was used to determine the BGaN/GaN alignment with decent precision. The value was found to be -0.3 ± 0.1 eV.