湿法化学腐蚀研究GaN薄膜中的位错

Study on the Dislocations in GaN Films by Wet-Chemical Etching

采用湿法化学腐蚀结合扫描电子显微镜、阴极荧光谱仪手段对GaN(0001)/Al2O3中的位错进行了研究。实验以熔融的浓度比为1∶1的KOH-NaOH溶液加入质量分数为10%的MgO,对样品进行腐蚀处理,得出优化腐蚀温度400℃、腐蚀时间2.5min。通过对GaN样品表面及剖面的扫描电子显微镜(SEM)图像和阴极荧光CL谱线图、影像图的分析,获得了GaN薄膜中存在的螺位错、刃位错和混合位错的分布特性及密度,并发现薄膜中的位错自衬底沿生长方向延伸,且随薄膜厚度的增加而密度减少。实验还研究了腐蚀前后GaN光学性质的改变,发现造成影像图中位错被明亮的六角坑包围的原因是应力自衬底沿生长方向逐步释放影像,致使逐层腐蚀后薄膜的CL谱带边发光峰红移,且发光强度增强。

The dislocations in wetting-chemical etched GaN(0001)/Al2O3 were investgated by scanning electron microscopy(SEM)and cathodeluminescence(CL).The GaN films were etched by melting KOH and NaOH(1∶1)solution with 10% MgO.The optimized etching conditions were 400 ℃,2.5 min.By means of SEM observation,CL spectrum and CL mapping analysis,the distribution properties and density of dislocations in GaN films were obtained.It is found the dislocation spreads along growth direction away from substrates,and the density decreases with increasing thickness.The optical properties of GaN films before and after etching were investigated.From CL mapping,the dislocations are surrounded by bright hexangular pits.The CL spectrum shows the peak position of GaN is redshift caused by strain relaxation along growth direction,and the peak intensity is increasing.