极性是影响氮化镓（GaN）器件的重要性质，基于氮（N）极性GaN的功率器件已展示出超过2000V的击穿电压及极低的导通电阻，超过已报道的多数镓极性功率器件的最好记录。硅（Si）衬底上的N极性GaN功率器件，可同时具有性能优势和产业化成本优势，具有重要研究价值。然而，目前采用金属有机气相外延（MOVPE）技术在Si衬底上直接生长N极性材料，存在极性控制困难、薄膜粗糙和杂质浓度高等挑战，国内外尚未见报道。本项目拟开展Si衬底上N极性Ga(Al)N薄膜的MOVPE生长，从表面工程和表面成核两方面研究N极性控制机理；同时研究表面原子迁移和吸附/脱附相关的表面动力学过程，探究表面形貌和杂质浓度的综合调控机制，掌握在Si衬底上稳定可靠的N极性控制工艺，以及低表面粗糙度、低杂质浓度的高品质N极性GaN薄膜生长工艺。预期的研究成果，可为发展Si基N极性GaN功率器件及其产业化奠定基础。

Polarity is one of the significant properties of GaN devices. N-polar GaN based power devices have demonstrated over 2000V record-high breakdown voltage and ultra-low on-resistance, outperforming most of their Ga-polar counterparts. N-polar GaN power devices on Si(111) substrates, not only can be superior in device performance, but also cost-effective in volume production, and therefore desire adequate exploration. However, the direct growth of N-polar III-nitride films on Si(111) using metal-organic vapor phase epitaxy (MOVPE) is facing difficulties in polarity control, rough surface and high impurity content, and the relevant research is little in literature. Therefore, we propose to carry out research on the epitaxial growth of N-polar III-nitride films on Si(111) using MOVPE, to study the polarity control by surface engineering and in the nucleation process, and to study the surface kinetic processes including adatom diffusion, desorption and adsorption. We aim to understand the mechanism in polarity control and the universal mechanism controlling the surface morphology and impurity incorporation of the N-polar nitride films on Si substrates. The outcome of the research is expected to lay foundation for the growth of N-polar GaN power devices on Si substrate and for their real applications in industry.