The effect of a monolayer thick SiN film on the surface states of the AlN/GaN heterostructure grown by molecular beam epitaxy was investigated. It was revealed that the submonolayer SiN coating of the AlN surface leads to the formation of an ordered (√3 × √3)R30° structure. Further SiN film growth results in a Si-enriched SiN amorphous film formation. The Fermi level, pinned 1 eV above the valence band maximum of as-grown AlN, jumps 2.3 eV when (√3 × √3)R30° is formed, and then gradually goes to 3.1 eV with an increase in the thickness of the SiN film up to 4 monolayers. The motion of the Fermi level is a consequence of the evolution of surface states, as well as the appearance of donor-like states in a Si-enriched SiN film. The presence of donor-like states was confirmed when studying the effect of current collapse in enhancemet-mode HEMTs made of SiN/AlN/GaN heterostructures.

中文翻译：

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在 AlN/GaN 异质结构上原位形成 SiN 层期间表面状态的演变

研究了单层厚的 SiN 膜对通过分子束外延生长的 AlN/GaN 异质结构的表面状态的影响。结果表明，AlN表面的亚单层SiN涂层导致形成有序的（√3×√3）R30°结构。进一步的 SiN 膜生长导致形成富含 Si 的 SiN 非晶膜。费米能级比生长的 AlN 的价带最大值高 1 eV，在形成 (√3 × √3)R30° 时跃升 2.3 eV，然后随着 SiN 厚度的增加逐渐升至 3.1 eV薄膜多达 4 个单层。费米能级的运动是表面态演化的结果，以及在富硅 SiN 膜中出现类施主态。