半绝缘GaAs光电导开关体内热电子的光电导振荡特性

用波长为532 nm、脉冲宽度为5 ns的超短激光脉冲触发电极间隙为4 mm的半绝缘GaAs光电导开关，开关偏置电压从500 V开始以步长50 V逐渐增加，直到开关出现非线性电脉冲输出.研究表明，线性和非线性电脉冲波形均呈现出在经历一个主脉冲之后，其后跟随几个幅值较小且具有周期性和不同程度的减幅振荡.分析了开关体内载流子（热电子）的微观状态和输运过程，在直流偏置电场作用下，开关体内的热电子在电子-电子、电子-声子相互作用过程中，当它们的弛豫时间大于载流子的寿命时, 光电子的输运可通过迁移率变化引起光电导振荡, 这是开关输出电脉冲出现振荡的原因.关键词：光电导开关热电子弛豫光电导振荡

Characteristics of photoconductivity oscillation in semi-insulating GaAs photoconductive semiconductor switches

The 4 mm gap and 5 ns pulse width semi-insulating GaAs photoconductive switches were triggered by 532 nm laser pulse with gradual increase of bias voltage from 500 V in steps of 50 V until the emergence of nonlinear electrical pulse. The expermental results showed that the linear and nonlinear electrical pulse waveforms had smaller amplitude and varying degrees of oscillation reduction after going through a main pulse. Then the microscopic state and transport process of carriers (hot-electron) in the switch material were studied in detail using the quantum theory. It was found that in the DC bias electric field, when the relaxation time of the hot-electrons in the electron-electron and electron-phonon interaction process is longer than the carrier life, the photoconductivity oscillation can be caused by the change of mobility in the process of optoelectronic transport, which is the main cause for the output electrical pulse to show oscillations.