Strain modulation is crucial for heteroepitaxy such as GaN on foreign substrates. Here, the epitaxy of strain-relaxed GaN films on graphene/SiC substrates by metal-organic chemical vapor deposition is demonstrated. Graphene was directly prepared on SiC substrates by thermal decomposition. Its pre-treatment with nitrogen-plasma can introduce C–N dangling bonds, which provides nucleation sites for subsequent epitaxial growth. The scanning transmission electron microscopy measurements confirm that part of graphene surface was etched by nitrogen-plasma. We study the growth behavior on different areas of graphene surface after pre-treatment, and propose a growth model to explain the epitaxial growth mechanism of GaN films on graphene. Significantly, graphene is found to be effective to reduce the biaxial stress in GaN films and the strain relaxation improves indium-atom incorporation in InGaN/GaN multiple quantum wells (MQWs) active region, which results in the obvious red-shift of light-emitting wavelength of InGaN/GaN MQWs. This work opens up a new way for the fabrication of GaN-based long wavelength light-emitting diodes.

应变调制对于异质外延（例如异质衬底上的 GaN）至关重要。在这里，展示了通过金属有机化学气相沉积在石墨烯 / SiC 衬底上外延应变松弛 GaN 薄膜。通过热分解直接在 SiC 衬底上制备石墨烯。它用氮等离子体预处理可以引入 C-N 悬键，为后续的外延生长提供成核位点。扫描透射电子显微镜测量证实部分石墨烯表面被氮等离子体蚀刻。我们研究了预处理后石墨烯表面不同区域的生长行为，并提出了一种生长模型来解释 GaN 薄膜在石墨烯上的外延生长机制。显着地，发现石墨烯可有效降低 GaN 薄膜中的双轴应力，应变弛豫改善了 InGaN/GaN 多量子阱 (MQW) 有源区中的铟原子掺入，导致发光波长明显红移InGaN/GaN MQW。这项工作为GaN基长波长发光二极管的制造开辟了一条新途径。