标题： 自供电GaAs纳米器件中Shockley-Ramo双极光电流的几何整形 显示英文标题

标题： Geometrical Tailoring of Shockley-Ramo Bipolar Photocurrent in Self-powered GaAs Nanodevices

摘要： 双极光电响应——其中光电流极性随着激发波长、栅极电压或其他条件而反转——对于光学逻辑、类脑计算和成像至关重要。 与单极响应不同，双极行为能够实现直接的二进制编码和增强的光电检测对比度。 然而，在传统的光电导或光伏系统中，电子和空穴的同时且方向相反的传输通常会抑制极性切换。 最近在无隙材料中的自供电Shockley-Ramo（SR）光电响应也由于强而不可逆的电子-空穴不对称性仅表现出单极信号。 在此，我们通过利用可逆的电子-空穴不对称性，首次在GaAs纳米收缩器件中展示了双极SR光电响应。 GaAs中较长的载流子寿命使得通过几何结构可以对载流子动力学进行亚扩散长度控制。 通过调节纳米收缩附近多数电子和少数空穴的光载流子动力学，我们调制SR响应以表现出双极性。 在低激发条件下，光电子占主导；随着激发强度增加，区间散射填充了高能L谷，减少了电子贡献，并导致由光激发空穴逐渐主导所驱动的极性反转。 这些结果得到了SR理论的支持，表明纳米尺度几何工程结合可逆的电子-空穴不对称性，能够实现自供电的双极光电流响应，为先进光电子器件提供了新的途径。 显示英文摘要

摘要： Bipolar photoresponse - where photocurrent polarity reverses with excitation wavelength, gate voltage, or other conditions - is essential for optical logic, neuromorphic computing, and imaging. Unlike unipolar responses, bipolar behavior enables direct binary encoding and enhanced photodetection contrast. However, in conventional photoconductive or photovoltaic systems, the simultaneous and opposite-directional transport of electrons and holes often suppresses polarity switching. Recent self-powered Shockley-Ramo (SR) photoresponse in gapless materials also show only unipolar signals due to strong, irreversible electron-hole asymmetry. Here, we demonstrate for the first-time bipolar SR photoresponse in GaAs nanoconstriction devices by exploiting reversible electron-hole asymmetry. The longer carrier lifetimes in GaAs enable sub-diffusion-length control of carrier dynamics through geometry. By tuning photocarrier dynamics near the nanoconstriction for both majority electrons and minority holes, we modulate the SR response to exhibit dual polarities. At low excitation, photoelectrons dominate; as excitation increases, intervalley scattering populates higher-energy L-valleys, reducing electron contribution and leading to polarity reversal driven by the growing dominance of photoexcited holes. These results, supported by SR theory, show that nanoscale geometric engineering, together with the reversible electron-hole asymmetry, enables self-powered bipolar photocurrent responses, offering new routes toward advanced optoelectronic devices.