| 摘要: |
| 报道了一种基于半绝缘砷化镓(SI-GaAs)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-GaAs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. |
| 关键词: 太赫兹 光电导 载流子动力学 |
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| Temperature dependence of terahertz emission of interdigitated photoconductive antenna based on semi-insulating gallium arsenide |
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ZHAO Zhenyu
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College of Mathematics and Sciences,Shanghai Normal University
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| Abstract: |
| A novel semi-insulated GaAs interdigitated photoconductive antenna is presented in this paper and its THz emission waveform and spectra bandwidth are recorded at different exciting carrier density in temperature range from 4.2 K to 270 K.The experimental results show that the THz radiation amplitude reaches to maximum at 70 K.THz waveform and bandwidth depend on the temperature and exciting carriers density.For the high optical flux case,high photo-generated carrier density leads to the space charge screening.The negative lob of THz waveform decline s with the temperature′s increasing at high exciting carriers density.For the low optical flux case,THz waveform is unipolar and its spectral component shifts to low frequency with the decreasing temperature.The variation of bandgap as well as carriers mobility of SI-GaAs substrate under low temperature leads to Γ-L intervalley scattering,which dominate the carriers dynamics of antenna.For the high optical flux case,the temperature dependence of THz emission is dominated by the mobility due to the space charge screening effect.For the low optical case,the temperature idependence of THz emission is dominated by the Γ-L intervalley scattering. |
| Key words: terahertz photoconductor carriers dynamics |
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