Lee Woo-Jung, Ma Jin Won, Bae Jung Min, Jeong Kwang-Sik, Cho Mann-Ho, Kang Chul, Wi Jung-Sub
Department of Physics and Applied Physics, Yonsei University, Seoul 120-749, Korea.
Sci Rep. 2013;3:1984. doi: 10.1038/srep01984.
A principal cause of THz emission in semiconductor nanostructures is deeply involved with geometry, which stimulates the utilization of indirect bandgap semiconductors for THz applications. To date, applications for optoelectronic devices, such as emitters and detectors, using THz radiation have focused only on direct bandgap materials. This paper reports the first observation of strongly enhanced THz emission from Germanium nanowires (Ge NWs). The origin of THz generation from Ge NWs can be interpreted using two terms: high photoexcited electron-hole carriers (Δn) and strong built-in electric field (Eb) at the wire surface based on the relation . The first is related to the extensive surface area needed to trigger an irradiated photon due to high aspect ratio. The second corresponds to the variation of Fermi-level determined by confined surface charges. Moreover, the carrier dynamics of optically excited electrons and holes give rise to phonon emission according to the THz region.
半导体纳米结构中太赫兹发射的一个主要原因与几何结构密切相关，这促使人们将间接带隙半导体用于太赫兹应用。迄今为止，使用太赫兹辐射的光电器件（如发射器和探测器）的应用仅集中在直接带隙材料上。本文报道了首次观察到锗纳米线（Ge NWs）发出的太赫兹辐射显著增强。基于该关系，Ge NWs产生太赫兹的起源可以用两个因素来解释：高光激发电子 - 空穴载流子（Δn）和线表面的强内建电场（Eb）。第一个因素与由于高纵横比而触发辐照光子所需的大面积表面有关。第二个因素对应于由受限表面电荷决定的费米能级的变化。此外，光激发电子和空穴的载流子动力学根据太赫兹区域产生声子发射。
