Si衬底上侧向外延生长GaN的研究

Study on Epitaxial Lateral Overgrowth of GaN on Si Substrate

采用条形Al掩模在Si(111)衬底上进行了GaN薄膜侧向外延的研究。结果显示,当掩模条垂直于Si衬底[11-2]方向,也即GaN[10-10]方向时,GaN无法通过侧向生长合并得到表面平整的薄膜;当掩模条平行于Si衬底[11-2]方向,也即GaN[10-10]方向时,GaN侧向外延速度较快,有利于合并得到平整的薄膜。同时,研究表明,升高温度和降低生长气压都有利于侧向生长。通过优化生长工艺,在条形Al掩模Si(111)衬底上得到了连续完整的GaN薄膜。原子力显微镜测试显示,窗口区域生长的GaN薄膜位错密度约为1×109/cm2,而侧向生长的GaN薄膜位错密度降低到了5×107/cm2以下。

GaN films were grown on A1/Si alloy patterned Si （111） substrate and the influence of the orientation of the mask stripes, as well as the growth conditions, were studied. It was found that when the mask stripes are perpendicular to the Si [11-2] direction, i.e. the GaN [10-10] direction, the GaN films can not coalesce to form a continuous and flat surface. When the mask stripes are parallel to the Si [11-2] direction, i.e. the GaN [10-10] direction, GaN films with flat surface can be obtained. Meanwhile, the results show that high growth temperature and low pressure are favorable to lateral growth. By optimizing the growth condition, continuous and flat GaN films on Si （111） substrate with Al/Si alloy mask were obtained. Atomic force microscopy analysis shows that the dislocation density of the GaN layer grown in the window region is about 1×10^9/cm^2 while that of the laterally grown GaN layer is decreased to less than 5×10^7/cm^2.