Department of Physics, University of Cincinnati, Cincinnati, Ohio 45221-0011, USA.
Nano Lett. 2012 Oct 10;12(10):5389-95. doi: 10.1021/nl302767u. Epub 2012 Sep 19.
Using a new technique, transient Rayleigh scattering, we show that measurements from a single GaAs/AlGaAs core-shell semiconductor nanowire provide sensitive and detailed information on the time evolution of the density and temperature of the electrons and holes after photoexcitation by an intense laser pulse. Through band filling, band gap renormalization, and plasma screening, the presence of a dense and hot electron-hole plasma directly influences the real and imaginary parts of the complex index of refraction that in turn affects the spectral dependence of the Rayleigh scattering cross-section in well-defined ways. By measuring this spectral dependence as a function of time, we directly determine the thermodynamically independent density and temperature of the electrons and holes as a function of time after pulsed excitation as the carriers thermalize to the lattice temperature. We successfully model the results by including ambipolar transport, recombination, and cooling through optic and acoustic phonon emission that quantify the hole mobility at ∼68,000 cm(2)/V·s, linear decay constant at 380 ps, bimolecular recombination rate at 4.8 × 10(-9) cm(3)/s and the energy-loss rate of plasma due to optical and acoustic phonon emission.
利用一种新的瞬态瑞利散射技术，我们表明，从单个 GaAs/AlGaAs 核壳半导体纳米线的测量结果，可以提供关于光激发强激光脉冲后电子和空穴密度和温度随时间的演化的敏感和详细信息。通过带填充、带隙重整化和等离子体屏蔽，密集且热的电子空穴等离子体的存在直接影响复折射率的实部和虚部，从而以明确定义的方式影响瑞利散射截面的光谱依赖性。通过测量这种随时间变化的光谱依赖性，我们直接确定了脉冲激发后电子和空穴的热平衡时的热力学独立密度和温度，因为载流子与晶格温度达到热平衡。通过包括双极输运、复合和通过光声子发射冷却来成功地对结果进行建模，这定量地确定了空穴迁移率为约 68000 cm(2)/V·s、线性衰减常数为 380 ps、双分子复合率为 4.8×10(-9) cm(3)/s 以及等离子体由于光声子发射而损失的能量速率。
