高倍增模式下GaAs 光电导开关时间抖动机理研究

High-gain mode GaAs photoconductive semiconductor switches (GaAs PCSS) have important applications in ultrafast pulse power system. The time jitter of the GaAs PCSS is a critical parameter of the fine synchronization synthesis of the switches array. But both the characteristic and the mechanism of the GaAs PCSS time jitter are not clear. In this project, a new testing method is proposed to eliminate the time jitter of the testing device effectively. The random time fluctuation at the rising edge of the output electrical pulses is related to the generation and the microscopic transportation mechanism of GaAs carrier associated with the multi-energy valley structure of GaAs material. The statistical rules of the time jitter in the GaAs PCSS will be explored under the high gain mode. The impact of micro-factors, such as, the light absorption, the carrier generation, the carrier multiplication, the carrier inter-valley transition, and the carrier microscopic transportation are considered integrated on analyzing the stability of the output electrical pulses. The differences and the nature of the time jitter of the GaAs PCSS will be discussed both in the negative differential mobility electric field region and the outside. The theoretical model of the time jitter in the GaAs PCSS based on the cooperation of multiple parameters, such as the trigger laser’s, the bias electric field’s and the GaAs PCSS’ will be established. Then these characteristic parameters will be optimized to find out the physical limitation of the time jitter in the GaAs PCSS. The research on the physical nature of GaAs PCSS time jitter will lay a foundation for the further applications, such as the fine synchronization synthesis of the GaAs PCSS array.

高倍增模式GaAs光电导开关（GaAs PCSS）在超快脉冲功率领域具有重要应用。其时间抖动性能是决定开关阵列精同步合成等的关键指标，但该模式下GaAs PCSS时间抖动的特性规律及物理机理尚不清楚。本研究拟采用能够有效消除测试仪器自身抖动的新方法，建立开关输出电脉冲上升沿随机涨落与GaAs多能谷结构相关的载流子产生及微观输运特性的内在联系，得到GaAs PCSS在高倍增模式下的时间抖动规律；剖析光吸收方式、载流子倍增、载流子谷间跃迁、载流子微观输运等机制对GaAs PCSS输出特性影响的本质，揭示偏置在负微分迁移率电场区内外的GaAs PCSS时间抖动差异的产生机理，获得GaAs材料、触发光、偏置电场等多参数调控下的GaAs PCSS时间抖动理论模型；进而通过优化光电条件及开关参数，探索GaAs PCSS时间抖动的物理极限，为提升GaAs PCSS在精同步合成等领域的应用奠定理论基础。

具有重复频率高、功率容量大性能的GaAs光电导开关是脉冲功率系统的首选开关器件，其兼具的皮秒量级抖动在保证输出脉冲稳定性的同时，有助于实现多开关高同步性下的功率最大化及系统小型化，在探地雷达、武器点火、超宽带辐射源等国防现代化高精尖领域都具有深远的应用价值。本课题建立了开关输出电脉冲前沿时间涨落和载流子微观输运间的内在关联，获得GaAs材料、触发光、偏置电场等宏观参数对GaAs PCSS时间抖动的影响权重，得到了由多宏观参数共同调控、且适用于线性及高倍增模式GaAs PCSS的时间抖动理论模型，并通过蒙特卡罗方法明晰了对应的输运特性及成因。实验获得了GaAs PCSS时间抖动与触发光脉宽、触发光能量相对涨落的正比关系。并基于处于微分迁移率电场区的GaAs PCSS在不同分光方式和光子能量差异下的抖动实验规律，得到了与能带结构相关的光吸收机制、载流子谷间跃迁机制、载流子微观输运等机制对GaAs PCSS输出特性及开关时间抖动的调控作用关系；基于多参量共同调控的开关时间抖动模型，分析了圣地亚实验室的高倍增模式GaAs PCSS时间抖动的实验结果，得到了开关抖动与输出脉冲上升时间和受载流子倍增率调控的载流子浓度相对涨落乘积的正比关系；并通过实验获得了弱光触发下高倍增GaAs PCSS的载流子倍增率与偏置电场关系，利用Silvaco软件验构架了高倍增模式下GaAs PCSS的倍增及输运模型，再现了高场畴形成及输出上升沿压缩的演化过程。使用VASP软件得到了掺杂和应力对半导体材料费米能级附近能量态的调控规律，为通过掺杂和应力等方式调节能带结构及带隙，调控光生载流子的输运特性提供了参考。该项目的研究为解决GaAs PCSS阵列在精同步控制、武器点火、超宽带辐射源等多个相关领域应用的关键性问题提供理论和实验依据。