发表机构
Old Dominion University; Thomas Jefferson National Accelerator Facility（老道明尼大学; 托马斯·杰斐逊国家加速器设施）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究通过MOCVD生长应变GaAs/GaAsP超晶格光电阴极，冷却至195 K时获95.0%±2.4%的电子自旋极化度，明确两种去极化机制，证实195 K冷却为实用的高极化GaAs基电子源制备途径。
AI 中文摘要
我们报告了通过金属有机化学气相沉积（MOCVD）生长并冷却至干冰温度（195 K）的应变GaAs/GaAsP超晶格光电阴极，其电子自旋极化度达到95.0±0.8（统计）±2.4（系统）%。我们在97.8%的圆偏振激发光和峰值极化波长下实现了0.7%的量子效率，该测量值超过了此前二十年中报道的、聚集在92%附近的GaAs基光电阴极极化度。我们改变阴极温度，在295 K、273 K、195 K和77 K下测量极化度和量子效率光谱：极化度从295 K时的91.2(1)%上升至195 K时的最大值，而光谱峰值在整个温度范围内从775 nm移动至739 nm（78 meV），跟踪带隙的展宽。这些光谱探测到两种去极化机制：冷却时被抑制的热化输运通道，以及持续存在并决定低温饱和的能量相关热电子弛豫。极化度在完整的冷却-升温循环后恢复，且在量子效率衰减时保持稳定，这表明表面能量过滤并非极化度提升的起源。这些结果表明，冷却至195 K（干冰即可实现）是获得更高极化度GaAs基电子源的实用途径。
英文摘要
We report electron spin polarization of 95.0 +/- 0.8 (stat) +/- 2.4 (sys)% from a strained GaAs/GaAsP superlattice photocathode grown by metalorganic chemical vapor deposition (MOCVD) and cooled to dry-ice temperature (195 K). We achieved this polarization with 97.8% circularly polarized excitation light and a quantum efficiency of 0.7% at the peak polarization wavelength. This measurement exceeds the values of previously reported GaAs-based photocathode polarizations, which have clustered near 92% for two decades. We vary the temperature of the cathode and measure the polarization and quantum-efficiency spectra at 295 K, 273 K, 195 K, and 77 K. The polarization rises from 91.2(1)% at 295 K to its maximum at 195 K, while the spectral peak shifts from 775 nm to 739 nm (78 meV) over the full temperature range, tracking the widening band gap. The spectra probe two depolarization mechanisms: a thermalized transport channel that is suppressed on cooling, and energy-dependent hot-electron relaxation that persists and sets the low-temperature saturation. The polarization recovers after a full cooling and warmup cycle and is stable while the quantum efficiency decays, which disfavors surface energy filtering as the origin of the gain. These results indicate that modest cooling to 195 K, for which dry ice suffices, is a practical route to higher-polarization GaAs-based electron sources.
Comments7 pages, 3 figures; Supplemental Material contains 8 pages, 3 figures, and 1 table. Ancillary files contain the measured spectra and a Jupyter notebook that reproduces figures and values, also archived at https://doi.org/10.5281/zenodo.22212862
