Yildirim Can, Ballet Philippe, Santailler Jean Louis, Giotta Dominique, Obrecht Rémy, Tran Thi Thu Nhi, Baruchel José, Brellier Delphine
Universite Grenoble Alpes, CEA, 17 Avenue de Martyrs, 38000 Grenoble, France.
European Synchrotron Radiation Facility, 74 Avenue de Martyrs, 38000 Grenoble, France.
J Synchrotron Radiat. 2021 Jan 1;28(Pt 1):301-308. doi: 10.1107/S1600577520014149.
High-quality HgCdTe (MCT) single crystals are essential for two-dimensional infrared detector arrays. Crystal quality plays an important role on the performance of these devices. Here, the dislocations present at the interface of CdZnTe (CZT) substrates and liquid-phase epitaxy grown MCT epilayers are investigated using X-ray Bragg diffraction imaging (XBDI). The diffraction contributions coming from the threading dislocations (TDs) of the CZT substrate and the MCT epilayers are separated using weak-beam conditions in projection topographs. The results clearly suggest that the lattice parameter of the growing MCT epilayer is, at the growth inception, very close to that of the CZT substrate and gradually departs from the substrate's lattice parameter as the growth advances. Moreover, the relative growth velocity of the MCT epilayer around the TDs is found to be faster by a factor of two to four compared with the matrix. In addition, a fast alternative method to the conventional characterization methods for probing crystals with low dislocation density such as atomic force microscopy and optical interferometry is introduced. A 1.5 mm × 1.5 mm area map of the epilayer defects with sub-micrometre spatial resolution is generated, using section XBDI, by blocking the diffraction contribution of the substrate and scanning the sample spatially.
高质量的碲镉汞（MCT）单晶对于二维红外探测器阵列至关重要。晶体质量对这些器件的性能起着重要作用。在此，利用X射线布拉格衍射成像（XBDI）研究了碲锌镉（CZT）衬底与液相外延生长的MCT外延层界面处的位错。在投影形貌图中使用弱束条件分离来自CZT衬底和MCT外延层的穿透位错（TDs）的衍射贡献。结果清楚地表明，生长中的MCT外延层的晶格参数在生长开始时与CZT衬底的晶格参数非常接近，并随着生长的进行逐渐偏离衬底的晶格参数。此外，发现TDs周围的MCT外延层的相对生长速度比基体快两到四倍。此外，还介绍了一种快速替代方法，用于探测位错密度低的晶体，以替代传统的表征方法，如原子力显微镜和光学干涉测量法。通过阻挡衬底的衍射贡献并对样品进行空间扫描，利用截面XBDI生成了具有亚微米空间分辨率的外延层缺陷的1.5 mm×1.5 mm区域图。
