School of Mechanical and Advanced Materials Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Korea.
Nanotechnology. 2012 Nov 2;23(43):435603. doi: 10.1088/0957-4484/23/43/435603. Epub 2012 Oct 11.
Today, state-of-the-art III-Ns technology has been focused on the growth of c-plane nitrides by metal-organic chemical vapor deposition (MOCVD) using a conventional two-step growth process. Here we show that the use of graphene as a coating layer allows the one-step growth of heteroepitaxial GaN films on sapphire in a MOCVD reactor, simplifying the GaN growth process. It is found that the graphene coating improves the wetting between GaN and sapphire, and, with as little as ~0.6 nm of graphene coating, the overgrown GaN layer on sapphire becomes continuous and flat. With increasing thickness of the graphene coating, the structural and optical properties of one-step grown GaN films gradually transition towards those of GaN films grown by a conventional two-step growth method. The InGaN/GaN multiple quantum well structure grown on a GaN/graphene/sapphire heterosystem shows a high internal quantum efficiency, allowing the use of one-step grown GaN films as 'pseudo-substrates' in optoelectronic devices. The introduction of graphene as a coating layer provides an atomic playground for metal adatoms and simplifies the III-Ns growth process, making it potentially very useful as a means to grow other heteroepitaxial films on arbitrary substrates with lattice and thermal mismatch.
如今，先进的 III-N 技术专注于通过金属有机化学气相沉积（MOCVD）使用传统的两步生长工艺来生长 c 面氮化物。在这里，我们展示了使用石墨烯作为涂层可以在 MOCVD 反应器中一步生长蓝宝石上的异质外延 GaN 薄膜，简化了 GaN 生长工艺。研究发现，石墨烯涂层改善了 GaN 和蓝宝石之间的润湿性，并且只需约 0.6nm 的石墨烯涂层，蓝宝石上的外延 GaN 层就会变得连续和平坦。随着石墨烯涂层厚度的增加，一步生长 GaN 薄膜的结构和光学性能逐渐向传统两步生长方法生长的 GaN 薄膜过渡。在 GaN/石墨烯/蓝宝石异质体系上生长的 InGaN/GaN 多量子阱结构表现出高的内量子效率，允许使用一步生长的 GaN 薄膜作为光电设备中的“伪衬底”。引入石墨烯作为涂层提供了金属原子的原子游乐场，并简化了 III-N 生长工艺，使其成为在具有晶格和热失配的任意衬底上生长其他异质外延薄膜的潜在有用方法。
