A Systematic Study of the Electrical Properties of Grain Boundaries Formed by Wafer Bonding

本文提出了对共价半导体（硅）和离子半导体（氧化锌）晶界电学特性的系统研究，以建立晶界晶体学、掺杂剂浓度和电子态（内禀和外禀）之间的关系。这种基本关系的缺乏，在很大程度上是因为在制备可以在电和结构上表征的可控错取向的大而平坦的晶界区域方面存在困难。为了克服这一限制，以及控制晶界掺杂的浓度和类型，提出使用快速发展的“晶圆键合”技术来制备明确的晶界。所提出的研究的具体目标包括：硅扭转边界中具有角取向错误的缺陷态的数量和能量的函数依赖性；ZnO外延薄膜可以通过晶片键合形成晶界，并进一步扩展到确定ZnO晶界的单个和组合掺杂所产生的缺陷状态作为晶体取向错误的函数；并提出了用晶界缺陷态描述多晶半导体电特性的模拟方案。提议的研究将研究在先进电子系统中重要的多晶半导体的晶界电学特性，例如氧化锌基压敏电阻陶瓷（用于电涌保护系统）和由多晶硅制成的太阳能电池。了解这些特性将使材料科学家能够设计出满足未来高性能应用要求的改进材料。% % %

9616784 Clarke A systematic study of the electrical characteristics of grain boundaries in both a covalent semiconductor (silicon) and an ionic semiconductor (zinc oxide) is proposed in order to establish relationships between grain boundary crystallography, dopant concentration and electronic states, intrinsic and extrinsic. Such basic relationships are lacking in large part because of the difficulty in preparing large, flat areas of grain boundary of controlled misorientation that can be characterized both electrically and structurally. To overcome this limitation, as well as to control the concentration and type of grain boundary doping, it is proposed to use the rapidly developing technology of "wafer bonding" to prepare well-defined grain boundaries. Amongst the specific objectives of the proposed research are: the functional dependence of the number and energy of defect states with angular misorientation for twist boundaries in silicon; the demonstration that ZnO epitaxial films can be wafer bonded to form grain boundaries, and the subsequent extension to identifying the defect states produced by individual and combined dopants of ZnO grain boundaries as a function of crystallographic misorientation; and the development of a simulation scheme for describing the electrical characteristics of polycrystalline semiconductors in terms of the grain boundary defect states. %%% The proposed research will study the electrical properties of grain boundaries in polycrystalline semiconductors of importance in advanced electronic systems, such as zinc oxide-based varistor ceramics (used in electrical surge protection systems) and solar cells made from polycrystalline silicon. Understanding these properties will enable materials scientists to design improved materials that meet the requirements of tomorrow's high performance applications. %%%