Ⅱ-Ⅵ族化合物晶体的缺陷分析与退火改性

【作者】 张晓娜；

【导师】 介万奇；

【作者基本信息】 西北工业大学 ， 材料学， 2001， 硕士

【摘要】 生长态的CdZnTe晶体内常常存在各种缺陷，包括点缺陷、位错、Te沉淀相和Zn的成分偏析等。缺陷的大量存在使晶片不能满足作HgCdTe外延衬底的要求，希望通过退火来达到改善晶片性能的目的。 本文首先研究了晶片的腐蚀过程，观察随腐蚀程度的逐渐加深，晶片表面缺陷蚀坑形貌的变化。实验发现：晶界和沉淀相蚀坑的出现要先于位错蚀坑的出现。 对晶片内各种缺陷和性能进行了分析、测试，主要包括显微结构的观察、红外透过率的测定、摇摆曲线的测定和成分分析。对晶片的质量做了全面、客观的评价。不同晶锭上切下来的晶片性能差异较大，同一晶片上不同位置处的晶片性能也不相同。同一种缺陷往往表现出不同的形貌，而且往往几种缺陷伴生出现，排列成不同的花样。 在对晶片性能和缺陷分析的基础上，采用两阶段退火方法对晶片进行了退火处理，对比了晶片退火前后性能的变化。最为明显的变化是晶片红外透过率的提高，摇摆曲线半峰宽的加宽和Te沉淀相形态的改变。退火后晶体表面出现了一种类似孪晶界的缺陷。 改变退火参数做了多次退火实验，分析了不同退火条件（包括退火时间、退火温度以及冷却条件）对退火效果的影响。 在退火工艺中，一种低温退火工艺因其高的红外透过率和很小的摇摆曲线半峰宽引起了我们的注意。更多还原

【Abstract】 There are several kinds of defects including point defects, dislocations, Te precipitates and Zn segregation in the as-grown CdZnTe crystals. These defects are veiy harmful to the application of CdZnTe as the substrate of HgCdTe film epitaxy. It is expected to eliminate the defects through annealing. Observation on the variation of surface morphology during the etching process indicates that the grain boundary and Te pecipitates will be shown earlier than the dislocatins. The measurements on the microstructure, IR transmission, rocking curve and the composition distribution reveal that the defects and the properties of CdZnTe crystals change in a quite large region for the slices from different ingot, or even for different wafers of the same ingot. More than one kind of defects are often gathered together. To improve the properties of the crystals, slices are first annealed using a two step method. The most obvious change in the properties of CdZnTe wafers after annealing are the increase of IR transmission, the broadening in FWHM(full width at half-maximum) of rocking curves. The morphologes of Te precipates are changed after annealing. A new kind of defect similar to the twins on surface is also observed. Several annealing experiences are done by changing the annealing time, annealing temperature and the cooling rate. The effects of different annealing sequences on the CdZnTe properties are analysed. A special low temperature annnealing method at 4000C shows a great efficiency for improving the IR transmission properties and keeping the crystallity.更多还原