研究了MOCVD系统中原位SiN插入层对GaN薄膜应力和光学性质的影响。采用SiN插入层后, GaN薄膜的裂纹数量大大减少, 薄膜所承受的张应力得到了一定的释放。同时, GaN薄膜的缺陷密度降低一倍, 晶体质量得到了极大的改善。研究表明, 位错密度的降低在GaN薄膜中留存较大的残余应力, 补偿了降温过程中所引入的张应力。同样, 随着SiN插入层的应用, 低温PL谱的半峰宽降低, 薄膜光学质量提高。最后研究了PL谱发光峰与应力的关系, 得到了一个-13.8的线性系数。

High quality GaN epilayers have been grown on 6H-SiC substrate by metal organic chemical vapor deposition (MOCVD) using an in situ porous SiNx interlayer. It was found that the SiNx interlayer played a very important role in strain relief and the enhancement of quality of GaN epilayer. Optical microscope studies revealed that the crack line density was reduced to 0.29 mm-1. Furthermore, the in-plane stress of 1.58×10-3 was measured by Raman spectra, representing a significant strain relief. The relaxation was assisted by the reduction of dislocation density. Finally, a linear coefficient characterizing the relationship between the band gap and the biaxial stress of the GaN epilayer was obtained.