Amorphous and Nanocrystalline Semiconductors for Optoelectronic Applications: Photoconductors, Detectors and Sensors Based on a-Se Alloys and Optoelectronic Glasses

辐射探测和成像光电材料的DG计划包括对掺杂非晶硒砷合金（a-Se：As）的主要研究和对稀土掺杂玻璃和玻璃陶瓷（含纳米晶体）的补充研究。a-Se合金具有优于晶体半导体的一个明显的优点，即它们可以方便地在大面积上制造，这导致它们在平板X射线图像检测器中的广泛商业用途。长期目标是通过在材料和器件水平上的发现来扩展我们在掺杂a-Se合金基半导体和器件方面的科学和技术知识;并在基础水平上推进知识。下一代a-Se检测器的设计，特别是用于一般放射学、CT和断层合成，还需要对三层中使用的光电导体的电特性的广泛了解，例如漂移迁移率、载流子捕获和复合寿命、灵敏度、暗电流、过量噪声、热生成速率、X射线诱导效应（例如缺陷产生或损坏）和弛豫效应这些合金是老化并表现出弛豫效应的玻璃。鉴于加拿大光源（CLS）的可用性，我们打算继续在我们的研究中使用同步加速器设施，并继续与CLS工作人员合作;并继续与我们的工业伙伴将结果与实际探测器相关联。该研究计划将涵盖光电导体研究的各个方面，从现在到新的a-Se合金（掺杂），共同努力通过物理模型将探测器性能与基本半导体性能联系起来。它还将包括用于微束放射治疗的Sm 3+掺杂玻璃和玻璃陶瓷，其中我们需要准确测量CLS BMIT线处微束中的剂量分布（峰值剂量2 - 3 kGy，宽度20 um）。在这个DG计划中将有一些项目。典型例子：（a）研究新掺杂的a-Se合金的光电特性作为温度和电场的函数，朝向具有较低暗电流和较高外加场的增强的p-i-n结构（较厚的i层）。 (b)研究a-Se合金的光电导、MTF、DQE与X射线能量的关系，作为工作场、温度、总剂量和剂量率的函数。(d)研究X射线照射对光电导体性能的影响，从而对实际检测器的灵敏度和DQE的影响。(e)发现新的Sm掺杂光电玻璃（OEGs），是组织等效的更好的MRT剂量分布监测和解决当前的问题（能量依赖性）。这项工作的影响是产生新的知识掺杂的a-Se合金与新的组合物的设计和开发的下一代平板X射线探测器和新的OEGs的高剂量剂量测定。

The DG program on optoelectronic materials for radiation detection and imaging includes a major study on doped amorphous Se-As alloys (a-Se:As) and a complimentary study on rare-earth doped glasses and glass ceramics (containing nanocrystals). a-Se alloys have one clear distinct advantage over crystalline semiconductors that they can be conveniently fabricated over large areas, which has led to their extensive commercial use in flat panel x-ray image detectors. The long term objective is to build on strength by extending our scientific and technological knowledge on doped a-Se alloy based semiconductors and devices by discoveries at the material and device levels; and advancing knowledge at the fundamental level. The design of next generation a-Se detectors, in particular for use in general radiology, CT and tomosynthesis, also needs extensive knowledge of the electrical properties of the photoconductor used in the three layers, e.g. drift mobilities, carrier trapping and recombination lifetimes, sensitivity, dark current, excess noise, thermal generation rate, x-ray induced effects (such as defect creation or damage) and relaxation effects - these alloys are glasses that age and exhibit relaxation effects. Given the availability of the Canadian Light Source (CLS), we intend to continue to use of the synchrotron facility in our research and continue to collaborate with the CLS staff; and also continue with our industrial partner in relating results to practical detectors. The research program will encompass all aspects of photoconductor research from present to new a-Se alloys (doped) in a concerted effort to relate detector performance to fundamental semiconductor properties through physical models. It will also include Sm3+ doped glasses and glass ceramics for Microbeam Radiation Therapy in which we need to accurately measure the dose profile in the microbeam at the CLS BMIT line (peak dose 2 - 3 kGy with a width 20 um). There will be a number of projects within this DG program. Typical examples: (a) Study of optoelectronic properties of new doped a-Se alloys as a function of temperature and electric field toward enhanced p-i-n structures (thicker i-layer) with lower dark currents and higher applied fields. (b) Study of the x-ray energy dependence of photoconductivity of a-Se alloys, MTF, DQE as a function of operating field, temperature, total dose and dose rate. (d) Study of the effects of x-ray irradiation on the photoconductor properties and hence on the sensitivity and DQE of the actual detector. (e) Discovering new Sm-doped optoelectronic glasses (OEGs) that are tissue equivalent for better MRT dose distribution monitoring and addressing current problems (energy dependence). The impact of the work is the generation of new knowledge on doped a-Se alloys with new compositions for the design and development of next generation flat panel x-ray detectors and new OEGs for high-dose dosimetry.