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肖特基势垒等效应。此外，我们证实交流偏置电流穿透了样品（如氧化硅）的薄表面层，通常会阻挡直流电流。利用交流偏压，实现了部分硅片的无损EDMR测量。得到的EDMR频谱与使用常规方法（即直流偏置）时相同。使用交流偏置时信噪比更差；然而，由于噪声似乎来自外部，因此存在足够的空间来提高交流偏置技术的灵敏度。这种交流偏置技术可用于测量各种块状材料；此外，它还应适用于由直流偏置电流引起的氧化或还原破坏系统的系统。我们还提出了一种用于ESR辐照的开放式射频谐振器，以及一种获取选定区域信号强度的方法，这对观察EDMR是有效的。此外，本研究还获得了一些先进的实验结果。在局部光照下，获得了硅片的EDMR图像。我们表明，EDMR成像的局部照明可以是一个工具，通过它可以估计半导体的特性。在紫外发光二极管的照射下，首次观察到具有极高带隙能量的化合物半导体的EDMR光谱。通过这些结果，我们不仅可以无损地观察硅半导体器件的EDMR，还可以观察各种材料（如化合物半导体）的EDMR。

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.