Dynamics of Local Vibrational Modes in Semiconductors

本研究计划的目的是阐明半导体中缺陷和杂质配合物的局部振动模式（LVMs）动力学。研究重点是晶体半导体中的LVMs，包括质子注入和氘注入的Si和Ge中含氢和含氘配合物的拉伸模式，Si和GaAs中的受体和供体氢配合物，以及Si， Ge和GaAs中间隙O的反对称拉伸模式。利用瞬态漂白和光子回波测量来确定第一激发振动能级的居群寿命和消相时间。利用美国托马斯·杰斐逊国家加速器设施的自由电子激光器的短脉冲高功率可调谐红外辐射进行时间分辨非线性光学研究。在晶体半导体中，氢和氘相关模式与体声子的相互作用有很大的不同，它们之间的比较将有助于确定弛豫机制。将进行温度相关的研究，以阐明局部模式和晶体声子带之间的耦合机制。讨论了振动能量弛豫和传递通道、与弯曲模式的耦合以及局部结构和晶体位置在振动弛豫过程中的作用等几个重要问题。该研究项目为研究生和本科生提供跨学科领域的培训，包括现代光学、材料科学和计算建模。氢是半导体中最重要的杂质之一。氢在这些材料中的一个重要特性是它能够通过钝化缺陷来提高器件性能，这一过程今天被常规用于生产集成电路，如计算机的CPU和RAM。了解振动能量流的速率和途径对于理解这些器件中的热和电子刺激缺陷和杂质反应和迁移至关重要。本实验研究计划的目的是阐明晶体半导体中氢修饰缺陷和杂质配合物局部振动的微观动力学。这些基础研究需要相当低的缺陷或杂质浓度，以减少由于相互作用造成的影响，这通常导致材料的低红外吸光度。Thomas Jefferson国家加速器设施的自由电子激光器的短脉冲高功率可调谐红外辐射将用于高分辨率时间分辨红外吸收实验。在这些晶体材料中，氢和氘模式与体振动的相互作用大不相同，直接比较氢和氘模式的动力学将进一步支持能量交换机制的识别。研究生和本科生将在这个项目中接受的培训将为他们在工业、学术或政府中从事半导体或光学相关的有吸引力的职业做好准备

The aim of this research program is to elucidate the dynamics of local vibrational modes (LVMs) of defect and impurity complexes in semiconductors. The research focuses on LVMs in crystalline semiconductors, including the stretch-modes of hydrogen- and deuterium-containing complexes in proton- and deuteron-implanted Si and Ge, the acceptor- and donor-hydrogen complexes in Si and GaAs, and the anti-symmetric stretch-mode of interstitial O in Si, Ge, and GaAs. The population lifetime and the dephasing time of the first excited vibrational level will be determined using transient bleaching and photon-echo measurements. The time-resolved nonlinear-optical studies will be carried out with the short-pulse high-power tunable-infrared radiation of the Free-Electron Laser at the Thomas Jefferson National Accelerator Facility. A comparison between hydrogen- and deuterium-related modes, which have widely different interactions with bulk phonons in crystalline semiconductors, will assist in identifying the relaxation mechanism. Temperature-dependent studies will be performed to elucidate the coupling mechanism between the local modes and the crystal's phonon bands. Several important questions will be addressed regarding vibrational energy relaxation and transfer channels, the coupling to bending-modes, and the role of local structure and crystal site in the vibrational relaxation process. This research program provides training for graduate and undergraduate students in an interdisciplinary field including modern optics, materials science and computational modeling. %%%Hydrogen is one of the most prominent impurities in semiconductors. One important property of hydrogen in these materials is its ability to improve device performance by passivating defects, a process, which today is used routinely in the production of integrated circuits such as CPU and RAM for computers. Knowledge of the rates and pathways of vibrational energy flow is critical for understanding thermally and electronically stimulated defect and impurity reactions and migration in these devices. The aim of this experimental research program is to elucidate the microscopic dynamics of local vibrations of hydrogen-decorated defect and impurity complexes in crystalline semiconductors. These fundamental studies require fairly low defect or impurity concentrations to reduce effects due to interactions, which often results in low infrared absorbance of the material. The short-pulse high-power tunable-infrared radiation of the Free-Electron Laser at the Thomas Jefferson National Accelerator Facility will be employed for high-resolution time-resolved infrared absorption experiments. A direct comparison between the dynamics of hydrogen and deuterium modes, which have widely different interactions with bulk vibrations in these crystalline materials, will further support the identification of the energy exchange mechanism. The training that graduate and undergraduate students will receive while working on this project will prepare them for attractive semiconductor or optics related careers in industry, academe, or government.***