Cd_(1-x)Zn_xTe晶体退火条件的选择及Zn压对退火晶体质量的影响  

EFFECTS OF ANNEALING CONDITIONS ON THE CRYSTALLIZATION QUALITIES OF Cd_(1-x)Zn_xTe SLICES

作　　者：李宇杰[1] 张晓娜[1] 介万奇[1] 

机构地区：[1]西北工业大学凝固技术国家重点实验室,西安710072

出　　处：《物理学报》2001年第12期2327-2334,共8页Acta Physica Sinica

基　　金：国家杰出青年基金 (批准号 :5 982 5 10 9);国家自然科学基金 (批准号 :5 9982 0 0 6)资助的课题~~

摘　　要：采用传统Bridgman方法和加入acceleratedcruciblerotationtechnique的Bridgman(缩写为ACRT B)方法生长的Cd1 -xZnxTe(x=0 .0 4)晶体中存在有点缺陷、位错、杂质和Te沉淀等缺陷 .为了减少甚至消除这些缺陷 ,必须将生长后的CdZnTe晶片在Cd气氛下退火 .从Cd -Te和Cd0 .96 Zn0 .0 4Te的P T相图出发 ,详细讨论了CdZnTe晶体的气 固平衡条件 ,并以此为依据选择退火条件 ,对ACRT -B法生长的Cd0 .96 Zn0 .0 4Te晶体进行了退火实验研究 .实验结果表明 ,气氛中的Zn压在一定程度内高于平衡压力有利于晶体中多余Te向晶体表面扩散 ,即有利于消除Te沉淀 .但过高的Zn压会使晶体表面成分偏离原始的化学配比 .此时 ,晶体表面与气氛强烈的原子交换 ,将造成严重的表面损伤 ,形成一层结晶质量很差的表面层 .同时 ,Zn原子向晶内的扩散 ,抑制了退火过程中晶内杂质向晶体表面的扩散 .因此 ,在较低的Zn压下退火 (但仍处于气 固平衡范围内 ) ,能排除晶内杂质 .通过仔细研究不同条件下退火后晶片的结晶质量和断面成分分布 ,可以认为CdZnTe晶体的退火可分为去沉淀相退火、去杂质退火和均匀化退火几种 ,最佳的退火工艺应是多步骤。Defects such as point defects, dislocations, impurities and Te precipitates always exist in Cd1-xZnxTe (x = 0.04) crystals obtained by Bridgman and accelerated crucible rotation technique-Bridgman bulk crystal growth methods. It is important to anneal CdZnTe slices in Cd vapor to eliminate these defects. In this paper, the solid-vapor equilibrium for CdZnTe crystals is first discussed extensively based on the phase diagrams of Cd-Te and the P-T plot of Cd0.96Zn0.04Te. Through the annalysis, the annealing conditions for Cd1-xZnxTe crystals are optimized. Experimental results show that the Zn partial vapor pressure, which is higher than the equilibrium pressure within a certain range, can enhance the diffusion process of the excess Te towards the surface of the slices and thus eliminate Te precipitates. However, saturated Zn pressure causes Zn and Te concentration in surface layers of the slices far away from the stoichiometry. Intensive exchange of atoms between the slice surface and the vapor under this condition would lead to severe damage to the crystallization quality on the surface. The inter-diffusion of Zn also inhibits the outer-diffusion of impurities during annealing. Thus a lower Zn partial pressure, but still lies in the solid-vapor equilibrium area of the PLT plot, can help to drive out the impurities. According to the crystallization quality and the concentration distribution of slices annealed under different conditions, the annealing of CdZnTe wafers is classified into three kinds, namely de-precipitate annealing, de-impurity annealing and homogenizing annealing. The favorable annealing process should be a multi-step and multiperiod procedure.

关 键 词：Cd1-xZnxTe 退火 气-固平衡 晶体 锌压 Zn压 质量 Ⅱ-Ⅵ红外半导体材料 镉锌碲化合物 晶体缺陷 

分 类 号：O78[理学—晶体学]