高增益砷化镓光导开关中的光致电离效应

Photo-Ionization Effects in High Gain Gallium Arsenide Photoconductive Semiconductor Switches

研究了光致电离在高增益本征砷化镓(GaAs)光导开关(PCSS)中的效应。在高增益本征砷化镓光导开关中,各级流注发展由三个过程组成:光致电离、畴电子崩(DEA)和载流子碰撞电离雪崩生长。光致电离在本征砷化镓绝缘区中产生局部高载流子密度区域,提供了允许畴存在的局域环境。光致电离包括激光触发和流注的复合辐射两种情形。分析了光导开关的最优触发激光条件。通过计算机数值模拟,计算了在距离流注表面y≤30μm的范围内,平均光生载流子密度n(t=0)乘以该局域的特征尺度满足偶极畴成核条件:n(t=0)·y>10^(12)cm^(-2);探讨了流注的复合辐射在流注周围产生非平衡载流子的规律;发现了触发区域沿电场方向的长度阈值L_(EC),触发区域的特征长度L_(E)必须满足条件:L_(E)≥L_(EC)。

The photo-ionization effects in high gain intrinsic gallium arsenide （GaAs） photoconductive semiconductor switches （PCSS） are explored. In high gain GaAs PCSS, each stage in which the streamer is formed consists of photoionization and domain electron avalanche （DEA） and avalanche carrier growth. Photo-ionization effects create a local high carrier density region in which a local environment for the existence of the domain is provided. Photo-ionization effects include the laser trigger and recombination radiation originating from streamer. The optimum condition of optical trigger is discussed. It is computed that the recombination radiation produces excess carriers around streamer inside a local region about y ≤30 μm and the product of average carrier density n （t =0） times characteristic length y is larger than 10^12 cm 2, namely n （t = 0） ·y〉10^12 cm^-2. The characteristics of photoionization effects of streamer are investigated. The space threshold LEC （in the direction of electric field） of trigger region is found. The characteristic length LE of trigger region must be larger than LEC, namely LE〉LEC.