利用金属有机化合物气相外延沉积技术在2 inch (5.08 cm) Si(111)图形衬底上生长了GaN外延薄膜,在Al组分渐变AlGaN缓冲层与GaN成核层之间引入了AlN插入层,研究了AlN插入层对GaN薄膜生长的影响。结果表明，随着AlN插入层厚度的增加,GaN外延膜(002)面与(102)面X射线衍射摇摆曲线半峰全宽明显变小,晶体质量变好,同时外延膜在放置过程中所产生的裂纹密度逐渐减小直至不产生裂纹。原因在于AlN插入层的厚度对GaN成核层的生长模式有明显影响,较厚的AlN插入层使GaN成核层倾向于岛状生长,造成后续生长的n-GaN外延膜具有更多的侧向外延成分,从而降低了GaN外延膜中的位错密度,减少了GaN外延膜中的残余张应力。同时还提出了一种利用荧光显微镜观察黄带发光形貌来表征GaN成核层形貌和生长模式的新方法。

GaN thin films are grown on patternted 2 inch (5.08 cm) Si(111) substrates by metal organic vapour phase epitaxy (MOVPE). AlN interlayers with different thicknesses are introduced between the compostion-graded AlGaN buffer layers and the GaN seed layer in different samples, and the influence of AlN interlayer on the growth of GaN film is investigated. The results indicate that the full widths at half maximum (FWHMs) of (002) and (102) X-ray diffraction (XRD) rocking curves as well as the crack density are improved obviously with increasing AlN interlayer thickness. The AlN interlayer can change the growth mode of GaN seed layer. GaN seed layer tends to grow in islands mode with a thicker AlN interlayer. This leads to epitaxial lateral overgrown of subsequent n-GaN, which can decrease the density of dislocations and the residual tensile stress of GaN film. Besides, a new method for studying the morphology and growth mode of GaN seed layer by observing yellow luminescence using fluorescence microscope is presented.