Intrinsic Defects in Wide Bandgap Semiconductors: Study by Magnetic Resonance Techniques

[00:93784 . watkins]该程序是使用磁共振技术对宽带隙半导体中的固有缺陷（晶格空缺和宿主间隙原子）进行实验研究。主要的重点是氮化镓，但其他目前感兴趣的宽带隙半导体（AlN, ZnO, SiC，金刚石等）也可以研究。该程序的主要目的是识别固有缺陷，并探测它们的电子和晶格结构，它们的扩散特性，以及它们与材料中其他缺陷相互作用的性质。实验技术包括电子顺磁共振（EPR）和电子-核双共振（ENDOR），主要通过光学方法（ODEPR和ODENDOR）检测，但在适当的情况下也可以通过传统的EPR方法检测。实验方法是用2.5 MeV电子辐照产生本征缺陷，并用磁共振技术进行研究。这些研究包括在Lehigh的一个特殊设施中进行4.2 K的原位辐照，这在世界上是独一无二的，这使得ODEPR可以在预热之前研究产生的原始空位和间隙。随后的退火可以确定每一个迁移的动力学和它与杂质和其他缺陷的相互作用的性质，因为它被它们捕获。室温辐照还用于研究在该温度下稳定的本征缺陷，以及在较低温度下可移动的本征缺陷的捕获所产生的各种缺陷。晶格空位（缺失的原子）和间隙（多余的原子）总是存在于一个完美的晶体半导体中。因此，它们被称为“内在缺陷”，在现代半导体器件制造中涉及的所有无数加工步骤中起着至关重要的作用，同时也决定了最终器件的技术重要特性。对于目前被广泛研究的“宽禁带”半导体材料（如氮化镓）中这些重要缺陷的性质，目前基本上一无所知。氮化镓有望在可见光和紫外光谱区域的光学应用以及高温下的微电子应用方面取得进展。本程序的主要目的是首次确定这些属性。实验方法是通过高能电子辐照产生缺陷，当电子与晶格原子的原子核发生近碰撞时，晶格原子被直接撞出晶格位置。辐照是在足够低的温度下进行的，可以将产生的间隙和空位冻结到晶格中，以便进行直接的光谱研究。所采用的光谱方法包括各种磁共振方法，它们能够明确地识别缺陷，并探测感兴趣的特性——它们的电子和晶格结构，它们在晶格中的迁移特性，以及它们与材料中存在的其他缺陷相互作用的性质。

0093784WatkinsThe program is an experimental study of the intrinsic defects (lattice vacancies and host interstitial atoms) in wide bandgap semiconductors using magnetic resonance techniques. The primary emphasis is on GaN, but other wide bandgap semiconductors of current interest (AlN, ZnO, SiC, diamond, etc.) may also be studied. The broad purpose of the program is to identify the intrinsic defects, and to probe their electronic and lattice structures, their diffusional properties, and the nature of their interactions with other defects in the material. The experimental techniques include electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR), detected primarily by optical methods (ODEPR and ODENDOR), but also by conventional EPR methods, where appropriate. The experimental approach is to produce the intrinsic defects by 2.5 MeV electron irradiation for study by the magnetic resonance techniques. These studies include irradiation in situ at 4.2 K in a special facility at Lehigh, unique in the world, which allows ODEPR study of the pristine vacancies and interstitials which are produced, prior to warm-up. Subsequent annealing allows the determination of the kinetics of the migration of each and the nature of its resulting interaction with impurities and other defects as it becomes trapped by them. Room temperature irradiation is also utilized to study the intrinsic defects that are stable at this temperature, as well as the various defects produced by trapping of the intrinsic defects which are mobile at lower temperatures. Lattice vacancies (missing atoms) and interstitials (extra atoms) are always present in an otherwise perfect crystalline semiconductor. Labeled "intrinsic defects", they therefore play a vital role in all of the myriad processing steps involved in modern semiconductor device manufacture, as well as in determining the technologically important properties of the final device. Essentially nothing is presently known concerning the properties of these important defects in the currently widely studied "wide bandgap" semiconducting materials, such as gallium nitride, which promise advances for optical applications into the visible and ultraviolet spectral regions, as well as for microelectronic applications at elevated temperatures. The broad purpose of the present program is to determine these properties for the first time. The experimental approach is to produce the defects by high-energy electron irradiation, where a lattice atom is directly knocked out of its lattice site when the electron has a near collision with its nucleus. The irradiation is done at a low enough temperature to freeze the resulting interstitial and vacancy into the lattice for direct spectroscopic study. The spectroscopic methods employed involve the various magnetic resonance ones, which are uniquely capable of unambiguously identifying the defects, and probing the properties of interest -- their electronic and lattice structures, their migrational properties in the lattice, and the nature of their interactions with other defects present in the material.