高增益砷化镓光导开关中的特征量分析

Analysis of Characteristic Quantities in High Gain GaAs Photoconductive Semiconductor Switches

分析了高增益本征砷化镓光导开关(PCSS)中的几个重要参量,研究了光导开关的物理机制,发展了以畴电子崩(DEA)为基础的流注理论。提出了畴电子崩的3个必要条件:初始载流子密度n_(LD)≥3×10^(15)cm^(-3),耗尽层的空穴密度和积累层的电子密度至少其中之一能够超过畴电子崩的阈值n_(cs),非平衡载流子密度区域沿电场方向的特征长度ΔZ必须大于畴电子崩转变为局域流注时的生长畴宽度b。揭示了流注的光致电离效应产生的局域平均载流子密度的上限大约为10^(17)cm^(-3)·ps^(-1),能够为后代生长畴提供的初始载流子密度为3×10^(15)≤n(t=0)<10^(17)cm^(-3);流注的传播速度范围大约为2.97×10~8≤v_(pro)≤6.21×10~9cm/s。理论分析结果与实验观察一致。

Several significant characteristic quantities as well as physical mechanism in high gain intrinsic GaAs photoconductive semiconductor switches （PCSS） are analyzed. The model of the streamer on the basis of domain electron avalanche （DEA） is developed. It is presented that the DEA requires three necessary conditions： the lower limit of initial carrier density nLD≥3 × 10^15 cm^-3 , the local carrier density at least either in the depletion layer or in the accumulation layer of the DEA must exceed the threshold ncs, the characteristic length AZ of the activated region along the field must be larger slightly than the width b of the growing domain. The upper limit of the local carrier density created by photo-ionization from the streamer is approximately 10^17 cm ^-3 ·ps^-1, which implies that the carrier density provided for the successive growing domain is approximately 3 × 10^15≤ n （t= 0） 〈 10^17 cm^-3. Therefore the propagation velocity of streamer is approximately 2.97 × 10^8≤ Vpro≤6.21 × 10^9 cm/s. The results of this theoretical analysis are consistent with the reported experimental observations.