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通过对不同生长厚度GaN/SiC(n-n)的慢正电子研究,发现在GaN/SiC的界面中存在大量各种缺陷并在界面两端形成两个不同方向的电场. 这些缺陷的产生和SiC衬底表面制备以及GaN和SiC不同的热膨胀系数有关. 而缺陷中大量的带状缺陷在界面中形成一个费米能级钉扎(Fermi level pinning),它的存在使界面中存在一定高度的势垒,导致在界面两端的一定区域内形成两个不同方向的电场. 用VEPFIT模拟该电场的存在,分四层(GaN/Interface/SiC1/SiC2)进行拟合,得到了很好的拟
关键词:
正电子湮没
缺陷
半导体 相似文献
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利用单能慢正电子束流,对原生的和经过电子辐照的6H-SiC内的缺陷形成及其退火行为进行研究.发现在n型6H-SiC中,经过退火后缺陷浓度降低.这主要是因为在退火过程中缺陷和间隙子的相互作用所引起.n型6H-Si经过1400 oC、30 min真空退火后,在SiC表面形成一个大约20 nm的Si层,这是在高温退火过程中Si原子向表面逸出的有力证明.在高温退火中,在样品的近表面区域有一个明显的表面效应,既在这些区域的S参数整体较大,这种现象与高温退火中Si不断向表面逸出有关.经过10 MeV的电子辐照,在n型6H-SiC中,正电子有效扩散长度从86.2 nm减少至39.1 nm,说明在样品中由于电子辐照产生大量缺陷.但是对p型6H-SiC,经过10 MeV电子辐照后有效扩散长度变化不大,这与其中缺陷的正电性有关.同时还对n型6H-SiC进行了1.8 MeV电子辐照后的300 oC退火实验,发现退火后缺陷浓度不减反增,这主要是因为在退火过程中,一些双空位缺陷和Si间隙子互相作用从而产生了VC缺陷的缘故. 相似文献
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用单能慢正电子束和 X 射线衍射方法研究了 Al/n-GaSb 金属半导体异质结在不同温度退火的情况下的演变.采用三层模型既 Al/界面/GaSb 对 S-E 实验数据进行拟合.结果发现在未退火样品的 Al 和 GaSb 之间存在一个厚度大约5nm 的界面层.在经过400℃退火后,该界面厚度增加到约400nm,且 S 参数下降.这可能是由于在退火过程中,界面区域的原子在界面处相互扩散所引起的.Al 膜的 S_(Al)参数降低且效扩散长度 L_(Al)增加,说明 Al 膜内的空位缺陷经过退火被消除且进行结构重整,晶格结构不断变好的结果.衬底 GaSb 的 S_B 参数和有效扩散长度 L_B 的演变表明,经过250℃退火后,原有的正电子捕获中心消失:但是经进一步400℃退火,又产生了新的正电子捕获中心.这可能来源于其他类型的与 V_(Ga)相关缺陷的正电子捕获以及 Ga_(Sb)晶格反位引起的正电子浅捕获.X 射线衔射的测量结果证实了正电子方法的结论. 相似文献
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The defect changes in 6H-SiC after annealing and 10MeV electron irradiation have been studied by using a variable-energy positron beam.It was found that after annealing,the defect concentration in n-type 6H-SiC decreased due to recombination with interstitials.When the sample was annealed at 1400℃ for 30 min in vacuum,a 20-nm thickness Si layer was found on the top of the SiC substrate,this is a direct proof of the Si atoms diffusing to surface when annealed at high temperature stages.After 10MeV electron irradiation,for n-type 6H-SiC,the S parameter increased from 0.4739 to 0.4822,and the relative positron-trapping rate was about 27.878 times of the origin sample,this shows that there are some defects created in n-type 6H-SiC.For p-type 6H-SiC,it is very unclear,this may be because of the opposite charge of vacancy defects. 相似文献
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评述了国际正电子领域的新探测技术———寿命 动量关联技术.介绍了该技术的发展过程,讨论了该技术的分析方法,详细阐述了该技术在Ps形成和热化过程中的应用,并讨论了该技术在Ps化学上的应用.A new detection technique--age momentum correlation in international positron field is reviewed. The recent development is described and the analysis methods are discussed for the technique. The application of the technique in the positronium formation and thermalization processes are systematically summarized. Besides the application of the technique in Ps chemistry is discussed. 相似文献
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The microstructure of diamond films was studied by slow positron beam and Raman spectroscopy. For the Raman spectroscopy experiment on diamond films, a high fraction of the sp3 hybridized bond was detected in samples. Positron annihilation spectra analysis further illuminated that the concentration and types of defects were different in each sample. S-E curves of all samples showed that diamond crystal structures had obvious variation in each sample. These results indicated that positron annihilation spectroscopy was an effective means to measure microstructure of diamond films. 相似文献