Lei Yuchen, Ma Junwei, Luo Jiaming, Huang Shenyang, Yu Boyang, Song Chaoyu, Xing Qiaoxia, Wang Fanjie, Xie Yuangang, Zhang Jiasheng, Mu Lei, Ma Yixuan, Wang Chong, Yan Hugen
State Key Laboratory of Surface Physics, Key Laboratory of Micro and Nano-Photonic Structures (Ministry of Education), and Department of Physics, Fudan University, Shanghai, 200433, China.
Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing, 100081, China.
Nat Commun. 2023 Sep 1;14(1):5314. doi: 10.1038/s41467-023-41126-8.
The evolution of excitons from 2D to 3D is of great importance in photo-physics, yet the layer-dependent exciton polarizability hasn't been investigated in 2D semiconductors. Here, we determine the exciton polarizabilities for 3- to 11-layer black phosphorus-a direct bandgap semiconductor regardless of the thickness-through frequency-resolved photocurrent measurements on dual-gate devices and unveil the carrier screening effect in relatively thicker samples. By taking advantage of the broadband photocurrent spectra, we are also able to reveal the exciton response for higher-index subbands under the gate electrical field. Surprisingly, dark excitons are brightened with intensity even stronger than the allowed transitions above certain electrical field. Our study not only sheds light on the exciton evolution with sample thickness, but also paves a way for optoelectronic applications of few-layer BP in modulators, tunable photodetectors, emitters and lasers.
激子从二维到三维的演化在光物理学中具有重要意义，但二维半导体中依赖于层数的激子极化率尚未得到研究。在此，我们通过对双栅器件进行频率分辨光电流测量，确定了3至11层黑磷（一种与厚度无关的直接带隙半导体）的激子极化率，并揭示了相对较厚样品中的载流子屏蔽效应。利用宽带光电流光谱，我们还能够揭示栅极电场下高指数子带的激子响应。令人惊讶的是，暗激子在一定电场以上会被点亮，其强度甚至比允许跃迁的强度更强。我们的研究不仅阐明了激子随样品厚度的演化，还为少层黑磷在调制器、可调谐光电探测器、发射器和激光器等光电器件中的应用铺平了道路。
