Yamahara Kota, Mannan Abdul, Kawayama Iwao, Nakanishi Hidetoshi, Tonouchi Masayoshi
Institute of Laser Engineering, Osaka University, Osaka, 565-0871, Japan.
Graduate School of Energy Science, Kyoto University, Kyoto, 606-8501, Japan.
Sci Rep. 2020 Sep 3;10(1):14633. doi: 10.1038/s41598-020-71728-x.
Gallium nitride (GaN) is a promising wide-bandgap semiconductor, and new characterization tools are needed to study its local crystallinity, carrier dynamics, and doping effects. Terahertz (THz) emission spectroscopy (TES) is an emerging experimental technique that can probe the ultrafast carrier dynamics in optically excited semiconductors. In this work, the carrier dynamics and THz emission mechanisms of GaN were examined in unintentionally doped n-type, Si-doped n-type, and Mg-doped p-type GaN films. The photocarriers excited near the surface travel from the excited-area in an ultrafast manner and generate THz radiation in accordance with the time derivative of the surge drift current. The polarity of the THz amplitude can be used to determine the majority carrier type in GaN films through a non-contact and non-destructive method. Unique THz emission excited by photon energies less than the bandgap was also observed in the p-type GaN film.
氮化镓（GaN）是一种很有前景的宽带隙半导体，需要新的表征工具来研究其局部结晶度、载流子动力学和掺杂效应。太赫兹（THz）发射光谱（TES）是一种新兴的实验技术，能够探测光激发半导体中的超快载流子动力学。在这项工作中，对非故意掺杂的n型、硅掺杂的n型和镁掺杂的p型GaN薄膜中的载流子动力学和太赫兹发射机制进行了研究。在表面附近激发的光生载流子以超快的方式从激发区域移动，并根据浪涌漂移电流的时间导数产生太赫兹辐射。太赫兹振幅的极性可通过非接触和非破坏性方法用于确定GaN薄膜中的多数载流子类型。在p型GaN薄膜中还观察到了由小于带隙的光子能量激发的独特太赫兹发射。
