论文部分内容阅读
为了降低MOCVD外延生长Si基GaN的缺陷密度,尝试引入超晶格插入层。界面突变的超晶格插入层能有效地阻挡由缓冲层延伸出来的位错。即使超晶格本身也产生位错,但位错的产生率比阻挡率低,所以超晶格总体起阻挡作用,可以减少后续生长的HT-GaN(高温氮化镓)的位错密度。研究了超晶格厚度对HT-GaN的位错密度的影响,比较了超晶格厚度不同的3个样品,并采用高分辨双晶X射线衍射(DCXRD)对GaN进行结晶质量的分析,分别用H3PO4+H2SO4混合溶液和熔融KOH对样品进行腐蚀并用扫描电子显微镜(SEM)对腐蚀的样品进行观察。用H3PO4+H2SO4腐蚀过的样品比用KOH腐蚀过的样品的位错密度大,进一步验证了之前有报道过的H3PO4+H2SO4溶液同时腐蚀螺位错和混合位错而KOH只腐蚀螺位错。分析结果表明,引入适当厚度的超晶格插入层,可以有效地降低后续生长的GaN的位错密度。
In order to reduce the defect density of Si-based GaN grown by MOCVD epitaxy, an attempt was made to introduce a superlattice insertion layer. The intercalated superlattice insertion layer effectively blocks the dislocations that extend from the buffer layer. Even if the superlattice itself is dislocated, the dislocation rate is lower than the barrier rate. Therefore, the superlattice serves as a barrier in general and the dislocation density of the HT-GaN (high-temperature gallium nitride) grown subsequently can be reduced. The effect of superlattice thickness on dislocation density of HT-GaN was investigated. Three samples with different thickness of superlattice were compared. The crystal quality of GaN was analyzed by high resolution double crystal X-ray diffraction (DCXRD) The samples were etched with H3PO4 + H2SO4 mixed solution and molten KOH and the etched samples were observed with a scanning electron microscope (SEM). The samples with H3PO4 + H2SO4 corroded larger dislocation density than the samples with KOH corroded, further confirming the previously reported solution of H3PO4 + H2SO4 corrodes both screw dislocations and mixed dislocations while KOH etches only the screw dislocations. The results show that the introduction of a suitable thickness of the superlattice insertion layer can effectively reduce the dislocation density of the subsequently grown GaN.