体电导率和表面电导率对CdZnTe像素探测器性能的影响
Effects of Bulk and Surface Conductivity on the Performance of CdZnTe Pixel Detectors
摘要：
研究了体电导率和表面电导率对Pt接触的高阻CdZnTe（CZT）像素探测器性能的影响。我们强调体和表面电导率的不同的温度行为所指示的机制的差异。此外，在制造过程中形成的CZT表面上存在的薄（10-100 A）氧化层会影响体漏电流和表面漏电流。我们证明，所测得的I-V的体电流的依赖关系可以解释考虑CZT探测器作为一个金属-半导体-金属系统与两个背靠背肖特基势垒接触。高表面漏电流显然是由于低电阻率表面层的存在，该低电阻率表面层具有与本体材料显著不同的特性。该表面层对具有多触点几何形状的检测器中的电荷收集效率具有深远的影响;源自阴极的电场线的一部分与像素触点之间的表面区域相交，其中电离粒子产生的电荷被捕获。为了克服这种效应，我们在像素触点之间放置了一个薄电极网格;当网格被负偏置时，像素之间的间隙中的强电场迫使落在表面上的电子向触点移动，防止电荷损失。我们已经调查了这些影响，通过使用CZT像素探测器铟凸点键合到一个定制的超大规模集成电路读出芯片。
英文摘要：
We studied the effects of bulk and surface conductivity on the performance of high-resistivity CdZnTe (CZT) pixel detectors with Pt contacts. We emphasize the difference in mechanisms of the bulk and surface conductivity as indicated by their different temperature behaviors. In addition, the existence of a thin (10-100 A) oxide layer on the surface of CZT, formed during the fabrication process, affects both bulk and surface leakage currents. We demonstrate that the measured I-V dependencies of bulk current can be explained by considering the CZT detector as a metal-semiconductor-metal system with two back-to-back Schottky-barrier contacts. The high surface leakage current is apparently due to the presence of a low-resistivity surface layer that has characteristics which differ considerably from those of the bulk material. This surface layer has a profound effect on the charge collection efficiency in detectors with multi-contact geometry; some fraction of the electric field lines originated on the cathode intersects the surface areas between the pixel contacts where the charge produced by an ionizing particle gets trapped. To overcome this effect we place a grid of thin electrodes between the pixel contacts; when the grid is negatively biased, the strong electric field in the gaps between the pixels forces the electrons landing on the surface to move toward the contacts, preventing the charge loss. We have investigated these effects by using CZT pixel detectors indium bump bonded to a custom-built VLSI readout chip.
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