在蓝宝石(Al2O3)衬底上应用脉冲激光沉积技术(PLD)生长不同厚度的AlN缓冲层后进行GaN薄膜外延生长。采用高分辨X射线衍射仪(HRXRD)和扫描电子显微镜(SEM)对外延生长所得GaN薄膜的晶体质量和表面形貌进行了表征。测试结果表明: 相比直接在Al2O3衬底上生长的GaN薄膜, 通过生长AlN缓冲层的GaN薄膜虽然晶体质量较差, 但表面较平整; 而且随着AlN缓冲层厚度的增加, GaN薄膜的晶体质量和表面平整度均逐渐提高。可见, AlN缓冲层厚度对在Al2O3衬底上外延生长GaN薄膜的晶体质量和表面形貌有着重要的影响。

AlN buffer layers with various thicknesses were grown on sapphire substrates by pulsed laser deposition (PLD), and then GaN films were epitaxially grown. The crystalline quality and surface morphology of the as-grown GaN films were characterized by high-revolution X-ray diffraction (HRXRD) and scanning electron microscopy (SEM), respectively. It is found that GaN films grown with AlN buffer layer show a poorer crystalline quality but better surface morphology compared with GaN films without AlN buffer layer. Furthermore, when the AlN buffer layer thickness increases, both the crystalline quality and the surface morphology of GaN films are improved dramatically. In this regards, the thickness of AlN buffer layer plays an important role in achieving high crystalline quality and excellent surface morphology of GaN films.