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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 observed with SEM cutting along the growth direction of single crystal V SiC wafers, it was found that the secondary electron image of the existence of contrast. The performance of the first part of the more bright growth, the growth part of the bleak, the middle there are obvious mutations. In PVT grown with V SiC single crystal, the SiC single crystal contains both shallow donor N and deep host V, which are compensation semiconductors. Starting from compensating the semiconductor carrier concentration, the corresponding relationship between the secondary electron image contrast and the carrier concentration is established, which is well explained. The results show that with the decrease of shallow donor N, the concentration of n-type carriers gradually decreases during the growth of SiC single crystal. When the concentration is equal to V, the concentration of the carrier changes abruptly and can be reduced by 10 orders instantly. Slowly reduced again. It is this sudden change in carriers that causes the secondary electron image of the SEM.