Williams Kristopher W, Monahan Nicholas R, Evans Tyler J S, Zhu X-Y
Department of Chemistry, Columbia University, New York, New York 10027, USA.
Phys Rev Lett. 2017 Feb 24;118(8):087402. doi: 10.1103/PhysRevLett.118.087402.
The radiationless recombination of electron-hole pairs in semiconductors is detrimental to optoelectronic technologies. A prominent mechanism is Auger recombination, in which nonradiative recombination occurs efficiently by transferring the released energy-momentum to a third charge carrier. Here we use femtosecond photoemission to directly detect Auger electrons as they scatter into energy and momentum spaces from Auger recombination in a model semiconductor, GaSb. The Auger rate is modulated by a coherent phonon mode at 2 THz, confirming phonon participation in momentum conservation. The commonly assumed Auger rate constant is found not to be a constant, but rather decreases by 4 orders of magnitude as hot electrons cool down by ∼90 meV. These findings provide quantitative guidance in understanding Auger recombination and in designing materials for efficient optoelectronics.
半导体中电子 - 空穴对的无辐射复合对光电子技术是有害的。一种突出的机制是俄歇复合，其中通过将释放的能量 - 动量转移到第三个电荷载流子，非辐射复合有效地发生。在这里，我们使用飞秒光发射直接检测俄歇电子，当它们从模型半导体GaSb中的俄歇复合散射到能量和动量空间时。俄歇速率由2太赫兹的相干声子模式调制，证实了声子参与动量守恒。发现通常假定的俄歇速率常数不是一个常数，而是随着热电子冷却约90毫电子伏特而降低4个数量级。这些发现为理解俄歇复合以及设计高效光电子材料提供了定量指导。
