分子束外延HgCdTe/CdZnTe(211)B表面缺陷研究

Study on Surface Defect of HgCdTe/CdZnTe(211)B by MBE

HgCdTe材料的表面缺陷是造成探测器性能下降的主要原因之一。采用聚焦离子束(Focused Ion Beam,FIB)、扫描电子显微镜(Scanning Electron Microscope,SEM)和能量色散X射线光谱仪(Energy Dispersive X-ray Spectrometer,EDX)研究了碲锌镉(CdZnTe)基HgCdTe外延层的表面缺陷。通过分析不同类型缺陷形成的原因,确定缺陷起源于HgCdTe材料生长过程。缺陷的形状与生长条件关系密切。凹坑及火山口状缺陷与Hg缺乏/稍高生长温度、分子束源坩埚中材料形状变化造成的不稳定束流有关。金刚石状缺陷和火山口状/金刚石状复合缺陷的产生与Hg/Te高束流比、低生长温度相关。在5 cm×5 cm大小的CdZnTe(211)B衬底表面上生长出了组分为0.216、厚度约为6.06~7μm的高质量HgCdTe外延层。同时还建立了缺陷类型与HgCdTe薄膜生长工艺的关系。该研究对于制备高质量HgCdTe/CdZnTe外延层具有参考意义。

The surface defects of HgCdTe material are one of the main reasons for the performance degradation of the detector.Focused ion beam(FIB),scanning electron microscope(SEM)and energy dispersive X-ray spectrometer(EDX)were used to study the surface defects of the CdZnTe-based HgCdTe epitaxial layer.By analyzing the reasons for the formation of different types of defects,it was determined that the defects originate from the growth process of HgCdTe material.The shape of the defect is closely related to the growth conditions.The microvoid and the volcano-shaped defects are found to be correlated to the Hg deficiency or higher growth temperature.Moreover,the collapse of the material in the molecular beam epitaxy(MBE)effusion cells may cause the instability of the beam flux,which could also contribute to the formation of the above-mentioned defects.Diamond-like defects and diamond-volcano compound defects are related to higher Hg/Te ratio and lower growth temperature.A high-quality HgCdTe epitaxial layer with a composition of 0.216 and a thickness of 6.06-7 μm was grown on the surface of a 5 cm×5 cm CdZnTe(211)B substrate.At the same time,the relationship between the types of defects and the growth process of HgCdTe thin films was established.The research results have reference significance for the preparation of high-quality HgCdTe/CdZnTe epitaxial layers.