PVT生长掺V SiC单晶的扫描电镜二次电子像衬度

SEM Secondary Electron Imaging in the V-Doped SiC Growth by PVT

在用SEM观察沿单晶生长方向切割掺V SiC晶片时,发现其二次电子像存在衬度。表现为先生长部分较明亮,后生长部分较暗淡,中间存在明显突变。在用PVT生长掺V SiC单晶时,SiC单晶中同时含有浅施主N和深受主杂质V是补偿半导体。从补偿半导体载流子浓度计算出发,建立了二次电子像衬度与载流子浓度的对应关系,很好解释了这一实验现象。结果表明,SiC单晶生长过程中随着浅施主N的减少,n型载流子的浓度逐步减少;当其浓度与V相当时,载流子浓度突变,可瞬间减少10个量级,此后又缓慢减少。正是这种载流子的突变引发了扫描电镜二次电子像衬度。

When using SEM to observe cutting V-doped SiC wafers along the crystal growth direction, it is found that contrast exists in the secondary electron image. The first grown part is bright, the later grown part is gloomy, and significant abrupt exists in the middle part. When growing V-doped SiC single crystal by PVT （physical vapor transport）, both shallow donors N and deep acceptors V exist in SiC, it is compensated semiconductor. Based on the compensation calculation of the semiconductor carrier concentration, the corresponding relationship of secondary electron image contrast with the carrier concentration is established, the experimental phenomena is well explained. The results show that in SiC crystal growth process, with the reduction of shallow donor N, n-type carrier concentration is reduced gradually, when concentration of N is rather the same with V, the mutation of carrier concentration can he instantly reduced by 10 orders of magnitude, after which they slowly decrease. It is the carrier mutation causes the contrast of scanning electron microscope secondary electron image.