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报道了一种基于半绝缘砷化镓(SI-Ga As)叉趾结构光电导天线在不同光生载流子浓度注入条件下,温度在4.2~270 K之间的太赫兹(THz)发射频谱.实验结果表明当温度达到70 K时,其THz发射强度达到最大值.光生载流子浓度和温度共同主导了THz波形和带宽.高照度情况下,大的光生载流子浓度导致空间电荷屏蔽.在此情况下,温度上升导致THz振荡的第一波谷退化.低照度情况下,THz波形呈现单极振荡,且随温度下降发射频谱出现红移.低温导致SI-Ga As的能隙和载流子迁移率发生变化,导致载流子出现谷带间散射,这一机制主导了光电导天线载流子动力学行为.高照度情况下,光电导天线太赫兹发射频谱的温度倚赖特性由空间电荷屏蔽导致的载流子迁移率差异决定.低照度情况下,温度倚赖特性由谷带间散射决定.
A terahertz (THz) emission spectrum based on a SI-GaAs toe structure photoconductive antenna at temperatures between 4.2 and 270 K at different photo-carrier concentrations was reported. The experimental results show that the THz emission intensity reaches the maximum when the temperature reaches 70 K. The photo-generated carrier concentration and temperature jointly dominate the THz waveform and the bandwidth, and in the case of high illumination, the large photo-generated carrier concentration leads to the space charge shielding. In this case, the temperature rise leads to the degradation of the first trough of THz oscillation.The THz waveform exhibits monopole oscillation under low illumination, and the emission spectrum appears red-shifted with temperature drop.The low temperature leads to the energy gap and current-carrying of SI-GaAs The change of the submotility causes the valley-band scattering of carriers, which dominates the carrier dynamics of the photoconductive antenna.Under the condition of high illumination, the temperature dependence of the terahertz emission spectrum of the photoconductive antenna is determined by the space charge Shielded by the carrier mobility difference caused by the decision.In low light conditions, the temperature dependence of the decision by the inter-valley scattering.