Conductance Fluctuations in Amorphous Silicon

本研究项目的主要目的是阐明和研究氢化非晶硅（a-Si:H）电导波动的物理机制。我们实验室先前对a-Si:H中的1/f噪声和随机电报开关噪声的研究表明，噪声来自于电阻随时间变化的不均匀电流细丝，可能是由于键合氢的运动引起键重排，从而改变了材料的缺陷结构。非晶硅薄膜将在明尼苏达大学的射频等离子体增强化学气相沉积系统中合成，该系统的掺杂水平和沉积条件是系统地变化的。研究这些薄膜的随机电报噪声对温度和偏置的依赖性，以确定开关噪声是否来自电流微通道。随着a-Si:H薄膜性质的变化，将研究表征1/f噪声的非高斯统计量。最后，通过比较热功率和电导率激活能之间的差异来表征迁移率边缘的远程无序，并将其与这些薄膜的噪声行为以及光学和结构特性相关联。这些努力将大大提高我们对a- si（一种技术上重要的材料）波动现象的理解。氢化非晶硅（a-Si:H）越来越多地用于光伏器件、输入扫描仪、传真机、复印机和用于平板显示器的薄膜晶体管。所有这些都需要非晶半导体的大表面积优势。随着这些电子器件的体积越来越小，非晶硅中的基本电噪声最终限制了器件的性能。因此，如果非晶半导体要实现其技术潜力，对造成噪声现象的微观机制的理解是至关重要的。本研究项目的主要目的是阐明和研究这些机制，因为薄膜半导体的性质是系统变化的。我们实验室先前对氢化非晶硅中的电子噪声的研究发现，噪声本身表现出随时间的波动，即噪声具有噪声！噪声的噪声研究提供了有关材料中电子无序程度和远程相关性的重要信息。这项研究将大大提高我们对非晶硅波动现象的认识，特别是提高我们对无序固体中非线性弛豫过程的物理理解。* * *

9424277 Kakalios The principal aim of this research project is to elucidate and study the physical mechanisms underlying conductance fluctuations in hydrogenated amorphous silicon (a-Si:H). Previous studies of 1/f noise and random telegraph switching noise in a-Si:H in our laboratory suggest that the noise arises from inhomogeneous current filaments whose resistance varies in time, possibly due to the motion of bonded hydrogen inducing bonding rearrangements which alter the defect structure of the material. Amorphous silicon films will be synthesized in an rf plasma-enhanced chemical vapor deposition system at the University of Minnesota, for which the doping level and deposition conditions are systematically varied. The temperature and bias dependence of the random telegraph noise of these films will be investigated to determine if the switching noise arises from current microchannels. The non-Gaussian statistics which characterize 1/f noise will be investigated as the properties of the a-Si:H films are varied. Finally, the long-range disorder at the mobility edge will be characterized by comparing the difference between the thermopower and conductivity activation energies, and will be correlated with the noise behavior as well as with the optical and structural properties of these films. These efforts will significantly improve our understanding of the fluctuation phenomena in a-Si, a technologically important material. %%% Hydrogenated amorphous silicon (a-Si:H) is increasingly used in photovoltaic devices, input scanners, fax machines, photocopiers, and thin-film transistors for flat-panel displays. All of these require the large surface area advantages of amorphous semiconductors. As these electronic devices are made smaller, fundamental electrical noise in the amorphous silicon ultimately limits device performance. An understanding of the microscopic m echanisms responsible for the noise phenomena is therefore crucial if amorphous semiconductors are to achive their technological potential. The principal aim of this research project is to elucidate and study these mechanisms as the properties of the thin-film semiconductor are systematically varied. Previous studies of the electronic noise in hydrogenated amorphous silicon in our laboratory discovered that the noise itself exhibits time-dependent fluctuations, that is, the noise has noise! Studies of the noise of the noise provide important information concerning the degree of electronic disorder and long-range correlations in the material. This research will significantly advance our knowledge of fluctuation phenomena in amorphous silicon in particular, as well as improve our understanding of the physics of non-linear relaxation processes in disordered solids, in general. ***