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在Si(111)衬底上用金属有机化学气相沉积(MOCVD)设备生长了AlN和GaN薄膜。采用高分辨X射线衍射、椭圆偏振光谱仪和原子力显微镜研究了AlN缓冲层生长时的载气(H2)流量变化对GaN外延层的影响。椭圆偏振仪测试表明:相同生长时间内AlN的厚度随着H2流量的增加而增加,即H2流量增加会导致AlN生长速率的提高。原子力显微镜测试表明:随着H2流量的增加,AlN表面粗糙度也呈上升趋势。XRD测试表明:随着AlN生长时的H2流量的增加,GaN的(0002)和(1012)峰值半宽增大,即螺型穿透位错密度和刃型穿透位错密度增加。可能是由于AlN缓冲层的表面形貌较差,导致GaN的晶体质量有所下降。实验结果表明:采用较低的H2流量生长AlN缓冲层可以控制AlN的生长速率,在一定程度上有助于提高GaN的晶体质量。
AlN and GaN films were grown on a Si (111) substrate using a metal organic chemical vapor deposition (MOCVD) device. High-resolution X-ray diffraction, ellipsometer and atomic force microscopy were used to study the influence of flow rate of carrier gas (H2) on the growth of GaN epitaxial layer during the growth of AlN buffer layer. Ellipsometry showed that the thickness of AlN increased with the increase of H2 flow rate in the same growth time, that is, the increase of H2 flow resulted in the increase of AlN growth rate. Atomic force microscopy tests showed that: with the increase of H2 flow rate, the surface roughness of AlN is also on the rise. XRD results show that the peak half widths of (0002) and (1012) increase with the increase of H2 flow rate during AlN growth, that is, the threading threading dislocation density and the edge threading dislocation density increase. It may be due to the poor surface morphology of the AlN buffer layer, resulting in a decrease in the crystal quality of GaN. The experimental results show that AlN growth rate can be controlled by the growth of AlN buffer layer with lower H2 flow rate, which can help to improve the crystal quality of GaN to a certain extent.