Anada Satoshi, Yamamoto Kazuo, Sasaki Hirokazu, Shibata Naoya, Matsumoto Miko, Hori Yujin, Kinugawa Kouhei, Imamura Akihiro, Hirayama Tsukasa
Nanostructures Research Laboratory, Japan Fine Ceramics Center, 2-4-1 Mutsuno, Atsuta-ku, Nagoya, Japan.
Advanced Technologies Research and Development Laboratories, Furukawa Electric Co. Ltd, 2-4-3 Okano, Nishi-ku, Yokohama, Japan.
Microscopy (Oxf). 2019 Apr 1;68(2):159-166. doi: 10.1093/jmicro/dfy131.
The innate electric potentials in biased p- and n-type GaAs compound semiconductors and the built-in potential were successfully measured with high accuracy and precision by applying in situ phase-shifting electron holography to a wedge-shaped GaAs specimen. A cryo-focused-ion-beam system was used to prepare the 35°-wedge-shaped specimen with smooth surfaces for a precise measurement. The specimen was biased in a transmission electron microscope, and holograms with high-contrast interference fringes were recorded for the phase-shifting method. A clear phase image around the p-n junction was reconstructed even in a thick region (thickness of ~700 nm) at a spatial resolution of 1 nm and precision of 0.01 rad. The innate electric potentials of the unbiased p- and n-type layers were measured to be 12.96 ± 0.17 V and 14.43 ± 0.19 V, respectively. The built-in potential was determined to be 1.48 ± 0.02 V. In addition, the in situ biasing measurement revealed that the measured electric-potential difference between the p and n regions changed by an amount equal to the voltage applied to the specimen, which indicates that all of the external voltage was applied to the p-n junction and that no voltage loss occurred at the other regions.
通过对楔形砷化镓样品应用原位相移电子全息术，成功地高精度、高精准度测量了偏置的p型和n型砷化镓化合物半导体中的固有电势以及内建电势。使用低温聚焦离子束系统制备了具有光滑表面的35°楔形样品，以便进行精确测量。在透射电子显微镜中对样品施加偏置，并记录具有高对比度干涉条纹的全息图用于相移法。即使在厚度约为700nm的厚区域，也能以1nm的空间分辨率和0.01rad的精度重建p-n结周围清晰的相位图像。未加偏置的p型和n型层的固有电势分别测得为12.96±0.17V和14.43±0.19V。确定内建电势为1.48±0.02V。此外，原位偏置测量表明，p区和n区之间测得的电势差变化量等于施加到样品上的电压，这表明所有外部电压都施加到了p-n结上，并且在其他区域没有发生电压损失。
