Ultrafast spatiotemporal photocarrier dynamics near GaN surfaces studied by terahertz emission spectroscopy
Ultrafast spatiotemporal photocarrier dynamics near GaN surfaces studied by terahertz emission spectroscopy
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DOI：
10.1038/s41598-020-71728-x
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发表时间：
2020-09
影响因子：
4.6
通讯作者：
Kota Yamahara;A. Mannan;I. Kawayama;H. Nakanishi;M. Tonouchi
中科院分区：
文献类型：
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作者：
Kota Yamahara;A. Mannan;I. Kawayama;H. Nakanishi;M. Tonouchi
氮化镓（GaN）是一种有前途的宽带隙半导体，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，可以探测光激发半导体中的超快载流子动力学。在这项工作中，研究了无意掺杂的 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。表面附近激发的光载流子以超快的方式从激发区域行进，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以通过非接触、无损的方法确定GaN薄膜中的多数载流子类型。在 p 型 GaN 薄膜中还观察到由小于带隙的光子能量激发的独特太赫兹发射。
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.