光电导开关产生太赫兹电磁波双极特性分析

利用光电导体产生太赫兹电磁波(THz波)，THz远场辐射波形与光电导体材料的载流子寿命、偏置电场以及触发光有直接关系.用不同方法对低温GaAs(LT-GaAs)和半绝缘GaAs(SI-GaAs)光电导开关辐射的THz电磁波所呈现的双极特性进行了模拟计算.结果表明，LT-GaAs光电导开关辐射THz波呈现双极性的主要原因是光生载流子寿命小于一个THz波产生时间；而光生载流子寿命大于100ps的SI-GaAs光电导开关，在不同的实验条件（不同偏置电场、不同光脉冲能量）下，产生的THz波呈现双极特性的主要原因分别是载流子发生了谷间散射和空间电荷电场屏蔽. 关键词： 光电导开关 THz电磁波 载流子寿命 空间电荷屏蔽

Study of the dipole characteristic of terahertz wave emitted from photoconductor switches

In this paper,different methods are used to simulate the dipole characteristic of terahertz(THz)wave emitted from low-temperature grown GaAs(LT-GaAs)and Semi-insulting GaAs(SI-GaAs)photoconductive semiconductor switches.The results indicate that the main cause of the dipole characteristic of THz wave emitted from LT-GaAs is the lifetime of optical-generated carriers being shorted than the generation time.For SI-GaAs photoconductive semiconductor switches with lifetime of optical-generated carriers longer than 100ps,the dipole characteristic of THz waveforms is mainly caused by intra-valley scattering and space charge field screening under different experimental conditions(different bias field and different optical pulse energy).