拉曼面扫描表征氮掺杂6H-SiC晶体多型分布

Characterization of Polytype Distributions in Nitrogen-doped 6H-SiC Single Crystal by Raman Mapping

采用物理气相传输法(Physical Vapor Transport,PVT)沿[0001]方向生长了一个直径为2英寸的氮掺杂6H-SiC晶体.采用拉曼面扫描方法对晶体中多型的分布进行了细致表征,研究了SiC晶体生长过程中多型的产生和演化.在6H-SiC晶体中观察到了15R-SiC和4H-SiC两种多型.在拉曼面扫描得到的晶体多型分布图上观察到了两类次多型结构区域,一类是继承其生长界面上对应的次多型结构形成的次多型结构区;另一类是由温度、压力等生长条件波动导致在6H-SiC主多型中出现的15R-SiC多型结构区.第一类次多型结构区中掺入的氮元素较多,载流子浓度较高,并且随着晶体生长不断扩大;第二类次多型结构区对晶体结晶质量的影响较小,且提高生长温度可以抑制15R-SiC多型结构.

Nitrogen-doped 6H-SiC crystal with the diameter of 2-inch was grown along [0001] direction by physical vapor transport method.The spatial distribution of different polytypes such as 6H-SiC,4H-SiC and 15R-SiC was characterized by mapping Raman spectra.The formation and evolution of different polytypes were investigated during the growth progress.15R-SiC and 4H-SiC were observed in the as-grown 6H-SiC single crystal.Two different polytype regions are observed from the spatial distribution of different polytypes.One region originates from the growth interface of different polytypes.This region has higher nitrogen doping level and carrier concentration,and the area can become large during the growth process.The other region is dominated by 15R-SiC which appears in the main 6H-SiC due to the perturbation in growth temperature,pressure,etc.This region has less effect on the crystal quality,which could be inhibited by increasing the growth temperature.