Localized Electronic States in Amorphous Semiconductors

9403806泰勒技术摘要：金属硫化物玻璃是一种将氢化非晶硅等四面体配位的非晶态材料与传统的硫化物玻璃(如硒或硒砷)连接起来的模型系统。这项研究将回答有关金属硫化物玻璃的结构、缺陷和掺杂机制的问题，其中金属和硫化物原子都可以四面体配位。重要的问题涉及光学诱导顺磁的微观起源、光变暗以及潜在的掺杂机制。具体目标是(1)了解含金属硫化物玻璃的局域结构有序性的细节，(2)研究金属硫化物玻璃从低配位数到高平均配位数变化时的本征缺陷，(3)了解铜-砷-硒(S)系统中的p型掺杂机制，以及(4)加深对光变暗过程和导致光变暗的缺陷，特别是涉及光学各向异性的缺陷的理解。非技术摘要：为了使半导体作为电子设备使用，必须能够通过一种称为“掺杂”的过程来显著改变其电学性质。在原子有序性不好的大多数半导体(非晶态半导体)中，通常认为掺杂是不可能的。我们已经证明了在一类含硫非晶态半导体中进行低效掺杂的可行性。他们正在研究改善掺杂的方法并扩大我们对这一过程的理解。非晶态半导体还具有亚稳态的特性，其电子和光学特性可以改变。这些亚稳态有时对器件性能有害，比如薄膜晶体管随着时间的推移而退化，但有时它们是有用的，比如在无机光致抗蚀剂中使用光学诱导的折射率变化。我们将对这些亚稳态进行研究，以了解设计有用器件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. ***