AlGaN缓冲层结构对Si基GaN材料性能的影响

Si衬底与GaN之间较大的晶格失配和热失配引起的张应力使GaN外延层极易产生裂纹,如何补偿GaN所受到的张应力是进行Si基GaN外延生长面临的首要问题.采用金属有机化合物化学气相沉积(MOCVD)技术在4英寸(1英寸=2.54 cm)Si (111)衬底上制备了GaN外延材料并研究了不同AlGaN缓冲层结构对Si基GaN外延材料性能的影响,并采用高分辨X射线衍射仪(HRXRD)、原子力显微镜(AFM)、喇曼光谱以及光学显微镜对制备的GaN材料的性能进行了表征.采用3层A1GaN缓冲层结构制备了表面光亮、无裂纹的GaN外延材料,其(002)晶面半高宽为428 arcsec,表面粗糙度为0.194 nm.结果表明,采用3层A1GaN缓冲层结构可以有效地降低GaN材料的张应力和位错密度,进而遏制表面裂纹的出现,提高晶体质量.

Effect of AlGaN Buffer Structure on the Properties of Si-Based GaN Material

The tremendous lattice mismatch and the thermal mismatch lead to high tensile stress between the Si substrate and GaN epilayer,which results in high density of crack and thread dislocation in GaN epilayer grown on Si substrate.It is the most important issue to compensate the tensile stress of GaN epilayer.The effects of different A1GaN buffer layer structures on the material properties of the Si-based GaN epilayer prepared on 4-inch (1 inch=2.54 cm) Si (111) substrates by metalorganic chemical vapor deposition (MOCVD) technology were investigated.The properties of the fabricated GaN materials were characterized by high resolution X-ray diffraction (HRXRD),atomic force microscopy (AFM),Raman spectroscopy and optical microscope.The GaN epilayer material with smooth and crackless surface was prepared by using three A1GaN buffer layers.The full width at half maximum (FWHM) value of the symmetric (002) face rocking curve is about 428 arcsec,and the surface roughness is about 0.194 nm.The results show that the tensile stress and the dislocation density of GaN material are decreased effectively by using three A1GaN buffer layers structures,the appearance of the crack is restrained and the crystal quality of the GaN epilayer is improved.