热处理和淬火的未掺杂半绝缘LEC GaAs的均匀性

对未掺杂原生ＬＥＣＳＩＧａＡｓ单晶在５００～１１７０℃温度范围进行了单步、两步和三步热处理及淬火，研究了这种热处理对ＥＬ２分布的影响，并检测了位错和Ａｓ沉淀的变化。结果表明，６５０℃以上温度的热处理可以改善ＥＬ２分布均匀性，且在６５０～９５０℃温度范围的热处理中，ＥＬ２均匀性的改善与热处理后的降温速率无明显联系。此外，两步或三步热处理的样品中ＥＬ２分布甚至比单步热处理样品中更优。９５０℃以下的热处理和淬火对位错和Ａｓ沉淀无明显影响。但是１１７０℃热处理井淬火后位错密度增加大约３０％，Ａｓ沉淀消失。对经１１７０℃淬火的样品再进行８０Ｏ℃或９５０℃的热处理，Ａｓ沉淀重新出现。ＥＬ２分布的变化可能与点缺陷、位错和Ａｓ沉淀的相互作用有关。文中提出了这种相互作用的模型，利用该模型可解释不同条件热处理后ＥＬ２分布的变化。

Homogeneity of Annealed and Quenched LEC SI GaAs

Simple,two-step and three-step annealings and succeeding quenchings were carried out in a temperature range from 500℃ to 1170℃ for undoped LECSI GaAs Crystal wafers. The effects of the annealings on EL2 distribution were studied and the changes in dislocation density and As precipitates were also examined. The experiment results indicate that the annealing above 650℃ can improve the uniformity of EL2 distribution and, for the annealing at 650～950℃,the improvement of the uniformity of EL2 distribution is independent of cooling rate after the annealing.In addition,it seems that the uniformity of EL2 distribution in the sample which experienced the two-step or three step annealings is better than that in the samples which experienced only simple annealing.The annealing below 950℃ causes no considerable effects on both dislocation density and As precipitates.However,after a annealing at 1170℃ and succeeding quenching,the dislocation density increases by about 30% and the As precipitates disappear completely.When a annealing at 800 C or 950℃ is carried out for the samples that had experienced 1170℃ quenching,the As precipitates regenerate.The changes in EL2 distribution appear to be related to the interaction between dislocations and point defects and As precipitates.A model is presented to explain the interaction of defects and the change in EL2 distribution during annealing.