Development of Electrically Detected Magnetic Resonance for Detecting Paramagnetic Substances at Very Low Concentration

在这项研究中，我们开发了一种利用电检测磁共振(EDMR)检测半导体中极低浓度顺磁性物质的方法。我们新开发的交流偏置检测技术能够消除干扰电极与样品材料之间欧姆接触的影响，如肖特基势垒。此外，我们还证实，交流偏置电流穿透了样品的薄表面层，例如氧化硅，这通常会阻碍直流电流。利用交流偏置，实现了对部分硅片的EDMR无损测量。得到的EDMR谱与使用传统方法(即直流偏置)时的谱相同。当使用交流偏置时，信噪比更差；然而，由于噪声似乎来自外部，因此有足够的空间来提高交流偏置技术的灵敏度。该交流偏置技术可用于各种块状材料的测量，并适用于直流偏置电流引起的氧化或还原对系统的腐蚀。我们还提出了一种用于ESR辐照的开放式射频谐振器，以及一种获得选定区域信号强度的方法，该方法对观察EDMR是有效的。在部分光照条件下获得了硅板的EDMR图像。我们发现局域照明的EDMR成像可以作为一种工具来估计半导体的特性。我们还首次利用紫外光发光二极管照明观测到了具有很高禁带能级的化合物半导体的EDMR谱，从而使我们不仅可以对硅半导体器件而且可以对各种材料，如化合物半导体的EDMR进行无损观察。

In this study, we developed a method detecting paramagnetic substances at very low concentration in a semiconductor utilizing electrically detected magnetic resonance (EDMR). The AC bias detection technique, which we newly developed, enabled to cancel the effects, such as Shottky barriers, that disturbed the ohmic contact between the electrodes and a sample material. Further, we certified that the AC bias current penetrated the thin surface layer of a sample such as silicon oxide, which normally obstructed a DC current. Using the AC bias, non-destructive EDMR measurements of part of a silicon wafer were realized. The EDMR spectrum obtained was the same as that when using a conventional method (i.e., DC bias). SNR was worse when AC bias was used ; however, because the noise appeared to be coming from outside, ample room exists to improve the sensitivity of the AC bias technique. This AC bias technique can be applied to measure various bulk materials ; in addition, it should be applicable to systems in which oxidization or reduction caused by a DC bias current corrupts the system.We also proposed an open type RF resonator for ESR irradiation, and a procedure to obtain the signal intensity at the selected region, which were effective to observe EDMR.Further, some advanced experimental results were obtained in this research. The EDMR images of a silicon plate were obtained under partial light illumination. We showed that EDMR imaging by localized illumination can be a tool by which the characteristics of semiconductors can be estimated. We also firstly observed EDMR spectra of compound semiconductor, which had very high band-gap energy by using UV light emitting diode illumination.By these results, we made possible to observe EDMR of not only silicon semiconductor devices but also bulk various materials, such as a compound semiconductor non-destructively.