论文标题
通过超快电子显微镜成像的硼砷中的持续热载体扩散
Persistent hot carrier diffusion in boron arsenide single crystals imaged by ultrafast electron microscopy
论文作者
论文摘要
立方硼（BAS）由于其高导热率而有望用于微电子的热管理。最近，还探索了其作为光电材料的潜力。但是，由于可用的高质量晶体尺寸较小，测量其光载体传输性能仍然很具有挑战性。在这里，我们使用扫描超快电子显微镜（SUEM）直接可视化光激发荷载载流子在BAS单晶中的扩散。出乎意料的是，我们观察到低光通量的双极性扩散，持续的热载体动力学超过200个皮秒，这可以归因于声音和光学声子之间的较大频率差距，这是导致高导热率的相同功能。在较高的光通量下，我们观察到自发的电子孔分离。我们的结果表明，BAS是一种有吸引力的光电材料，结合了高热导电率和出色的光载体传输特性。我们的研究还证明了SUEM在新兴材料中探测光载体运输的能力。
Cubic boron arsenide (BAs) is promising for microelectronics thermal management due to its high thermal conductivity. Recently, its potential as an optoelectronic material is also being explored. However, it remains challenging to measure its photocarrier transport properties due to small sizes of available high-quality crystals. Here, we use scanning ultrafast electron microscopy (SUEM) to directly visualize the diffusion of photoexcited charge carriers in BAs single crystals. Surprisingly, we observed ambipolar diffusion at low optical fluence with persistent hot carrier dynamics for above 200 picoseconds, which can be attributed to the large frequency gap between acoustic and optical phonons, the same feature that is responsible for the high thermal conductivity. At higher optical fluence, we observed spontaneous electron-hole separation. Our results show BAs is an attractive optoelectronic material combining high thermal conductivity and excellent photocarrier transport properties. Our study also demonstrates the capability of SUEM to probe photocarrier transport in emerging materials.
