kHz弱光触发下非线性光电导开关的高倍增效应调控和击穿机理研究

In this proposal, we plan to investigate the switching stability and longevity of high gain GaAs photoconductive semiconductor switches (GaAs PCSS) at kHz repetition rate by µJ-nJ optical excitation. It will be carried out that the carriers’ transport featured with high gain mechanism and the heat effect of filament current are regulated and controlled. Based on the optimization of semiconductor band structure, ohmic contacts fabrication, optical excitation manner, the transportation of bunched photo-activated carriers is quenched periodically by the momentary electric field variation. The spatial and temporal development of filaments is regulated and then the transient electric field is uniformed. Furthermore, the heat accumulation is released and the conductive current could be increased further. Consequently, a stable switching with carriers’ high gain mechanism is obtained at kHz repetition rate. Using the optical pump and THz probe system, the influences between the heat mechanism and the transport of photo-activated charge domain, which is in the form of filament currents, is realized during the photon-electric field-heat effect highly coupling process. Therefore, the restrictive conditions of transient electric field in GaAs PCSS is obtained at repetition rate operation. In addition, the assessment system of non-linear operation of PCSS excited by µJ-nJ optical energy at kHz repetition rate, which refers to the rise time, pulse width, isolation characteristics and power capacity related to the repetition rate, is evaluated and achieved. Finally, the GaAs PCSS devices with the advantages of high gain mechanism are developed, which can operate at bias voltage up to 30 kV, current as high as 1kA, repetition frequency up to 50kHz, pulse width of the order of magnitude from several hundred picoseconds to tens nanoseconds.

围绕kHz重复频率/弱光（µJ-nJ）触发下非线性砷化镓光电导开关（GaAs PCSS）的工作稳定性和寿命问题，对调控开关内具有高倍增效应为特征的载流子输运过程和改善丝状电流发热机制进行深入研究。在优化GaAs能级结构、电极制备、触发光引入等基础上，采用电场猝灭的方法对光生载流子聚束输运过程进行周期性的提前关断，有效调控丝状电流的时间/空间发展来均匀瞬态电场分布、改善热积累、增强通流能力，实现kHz条件下载流子的高倍增稳定输出。结合光泵浦-太赫兹探测技术，认识在光子-电场-热效应高度耦合过程中发热机制对以丝状电流为具体表现形式的光生载流子成畴输运的影响，确定重复频率条件下的瞬态电场约束性条件。建立上升时间、脉宽、绝缘特性、功率容量以及重复频率等指标的综合评价体系。研制工作电压~30kV，电流~1kA量级，重复频率~50kHz，电流脉冲宽度亚ns到几十ns量级的GaAs PCSS器件。

围绕kHz重复频率/弱光（µJ-nJ）触发下的高倍增砷化镓光电导开关（GaAs PCSS）的工作稳定性和寿命问题，对调控开关内具有高倍增效应为特征的载流子输运过程和改善丝状电流发热机制进行深入研究。在优化GaAs能级结构、电极制备、触发光引入等基础上，研究了nJ光能触发条件下GaAs PCSS的瞬态工作特性，有效调控丝状电流的时间/空间发展来均匀瞬态电场分布、改善热积累、增强通流能力，实现1kHz条件下的载流子高倍增稳定输出，最高工作电场为80kV/cm。分析了光子-电场-热效应高度耦合过程中发热机制对以丝状电流为具体表现形式的光生载流子成畴输运的影响，确定重复频率工作条件下的瞬态电场约束条件。在μJ光能触发条件下，初步实现了对于光生载流子的调控，瞬态输出电脉冲幅值提高32倍的同时、宽度压缩比为76.9%。项目研究的系列结果为超快光电导器件的高功率大电流重复频率应用技术奠定了实验和理论基础。