Localized Electronic States in Amorphous Semiconductors

小行星9403806 技术摘要：金属硫族化物玻璃是一种模型系统，其提供了四面体配位的非晶材料（例如氢化非晶硅）与传统硫族化物玻璃（例如硒或硒化砷）之间的联系。 该研究将回答有关金属硫族化物玻璃中的结构，缺陷和掺杂机制的问题，其中金属和硫族化物原子可以四面体配位。 重要的问题涉及光致顺磁性的微观起源，光暗化，和潜在的掺杂机制。 具体目标是（1）了解含金属硫系玻璃中局部结构有序的细节，（2）研究金属硫系玻璃中结构从低平均配位数到高平均配位数变化时的本征缺陷，（3）了解Cu-As-Se（S）系统中的p型掺杂机制，以及（4）进一步理解光暗化过程和促成光暗化的缺陷，特别是涉及光学各向异性的那些缺陷。 非技术摘要：为了使半导体成为有用的电子器件，必须能够通过一种称为“掺杂”的过程显着改变其电特性。 在大多数原子没有很好地有序的半导体（非晶半导体）中，通常认为掺杂是不可能的。 我们已经证明了在一类含硫的非晶半导体中进行低效掺杂的可行性。 硒或碲，并正在研究如何改善掺杂和扩大我们的理解的过程。 非晶半导体还具有亚稳态的性质，并且它们的电子和光学特性可以改变。 这些折射率有时对器件性能有害，如薄膜晶体管随时间的降解，但有时它们是有用的，如在无机光致抗蚀剂中用于光诱导折射率变化。 这些可重复性将被研究，以了解有用的设备的设计所必需的基本微观机制。 ***

9403806 Taylor Technical abstract: Metal chalcogenide glasses are a model system that provides a link between the tetrahedrally-coordinated amorphous materials, such as hydrogenated amorphous silicon and the traditional chalcogenide glasses, such as selenium or arsenic selenide. The research will answer questions concerning the structure, defects and doping mechanisms in metal chalcogenides glasses where both the metal and chalcogenide atoms can be tetrahedrally coordinated. Important questions concern the microscopic origins of optically-induced paramagnetidm, of photodarkening, and potential doping mechanisms. The specific objectives are (1) to understand the details of the local structural order in metal-containing chalcogenide glasses, (2) to study the intrinsic defects in metal chalcogenide glasses as the structure is changed from low to high average coordination number, (3) to understand the p-type doping mechanism in the Cu-As-Se(S) systems, and (4) to further the understanding of the photodarkening process and the defects that contribute to photodarkening, especially those defects that involve optical anisotropies. Non-technical abstract: In order for semiconductors to be useful as electronic devices on must be able to change their electrical properties dramatically by a process called "doping". In most semiconductors where the atoms are not well ordered (amorphous semiconductors) it has generally been assumed that doping is not possible. We have demonstrated the feasibility of inefficient doping in a class of amorphous semiconductors containing sulfur. Selenium or tellurium and are investigating ways of improving the doping and expanding our understanding of the process. Amorphous semiconductors also have the property that they are metastable and that their electronic and optical characteristics can change. These metastabilities are sometimes deleterious to device performance, as in the degradation of thin-film transistors with time, but so metimes they are useful, as in the use for optically- induced index changes in inorganic photoresists. These metastabilities will be studied to understand the basic microscopic mechanism essential for the design of useful devices. ***