A new defect spectrosoopy using optical and electric noises : Application to a-Si : H

在本研究中，我们提出了一种新的缺陷光谱可以建立从光学和电学噪声测量。缺陷谱是对半导体（非晶半导体）中缺陷态密度和能级的测量，由于由电势涨落引起的宏观不均匀性被认为是光电导的主导因素，我们将噪声测量的重点放在氢化非晶硅（a-Si：H）和非晶硫族化合物（a-Ch）的光电流bith上。我们得到的结果总结如下：1.在a-Si：H中，长程电势波动主导“噪声（电流波动）”，因此这些效应掩盖了缺陷的影响。从噪声测量本身很难推断出缺陷的信息。因此，我们测量了交流光电导（在交流电场下的光电导），这是电流噪声之一。从这个测量中，我们得到了显着的结果，产生的潜在波动的程度（en 关于我们 能源和空间）。这已经在第19届<th>非晶和微晶半导体国际会议（法国尼斯，2001年8月）上作为特邀演讲报道。在a-Ch中，光辐照诱导各种光结构变化和缺陷产生，因此情况比a-Si：H更复杂。因此，我们首先专注于研究光结构变化的动力学。我们首次发现了“瞬态光结构变化”。这些论文发表在《物理评论》（快速通讯）和印刷版（2002年）上。在a-Ch中，缺陷由长时间的光照射引起，并且在长时间的光照射（亚稳态）后，电流噪声由缺陷主导。我们在第19届<th>非晶和微晶半导体国际会议（法国尼斯，2001年8月）上指出，交流光电流方法可以作为一种新的“缺陷光谱”。频率分辨光电导测量是一种有用的技术，它可以分解光响应的真实的和虚部。通过这种技术，可以获得光生载流子的寿命分布。这些应该与光致发光的寿命分布相比较。这些工作将继续进行。少

In the present study, we proposed that a new defect spectroscopy could be established from optical and electrical noise measurements. The term "defect spectroscopy" is evaluation of density and energy levels of defect states in semiconductors (amorphous semiconductors).As a macroscopic inhomogeneity originating from potential fluctuations is expected to dominate photoconductivity, we focused the noise measurements on photocurrent bith for hydrogenated amorphous silicon (a-Si : H) and amorphous chalcogenides (a-Ch). The results we obtained are summarized below :1. In a-Si : H, long-range potential fluctuations dominate "noise (current fluctuations)" and hence these effects mask the effect of defects. It is hard to deduce information of defects from noise measurement itself. Thus we measured AC photoconductivity (photoconductivity under ac electric field) which is one of current noises. From this measurement we got remarkable results which produce the extent of potential fluctuations (en … More ergy and space). This has been reported in 19^<th> Int. Conf on Amorphous and Microcrystalline Seminconductors (Nice, France, August 2001) as an invited talk.2. In a-Ch, photoirradiation induces various photostructural changes and defect creations and hence the situation is more complex than that for a-Si : H. Therefore, we first focused to study the dynamics of photostructural changes. We found the "transient photostructural changes" for the first time. These were published in Physical Review (rapid communication) and in print (2002).3. In a-Ch, defects are induced by prolonged photoirradiation and current noises are dominated by defects after prolonged photoirradiation (metastable state). We showed in 19^<th> Int. Conf on Amorphous and Microcrystalline Seminconductors (Nice, France, August 2001) that the ac photocurrent method can be useful as a new "defect spectroscopy".4. Frequency-resoloved photoconductivity measurement can be useful technique, in which real and imaginary parts of photo-response will be decomposed. Through this technique, life-time distribution of photocarriers can be obtained. These should be compared with the life-time distribution of photoliminescence. These works will be continued. Less