光激发单极畴与耿氏偶极畴的物理机制比较

Comparisons of Photon-Activated Monopole Domain and Gunn Dipole Domain

对比了半绝缘多能谷光电导开关中光激发单极畴和耿氏器件中偶极畴的物理机制.从产生机理、电场分布、电子浓度、生长和演变过程等多角度阐述光激发单极畴的特性.与偶极畴显著不同的是,光激发单极畴内仅有光生电子积累层,没有正离子层;光激发单极畴与光生空穴之间产生了一个与外加电场反向的电场,使畴前电场增强,畴头部电子浓度最高;光激发单极畴生长过程可以一直持续下去,终因电子碰撞电离演变为发光畴,如果碰撞电离达到雪崩强度,将演变为雪崩发光畴.最后,本文用光激发单极畴模型解释了光电导开关非线性工作模式的超快上升沿、发光电流丝、电流锁定现象等重要实验现象.

The photon-activated monopole domain in a semi-insulating multi-valley photoconductive semiconductor switch and the dipole domain in a Gunn device are compared. The generation mechanism, electric field distribution, electron concentration distribution,growth and evolution of the photon-activated monopole domain are discussed. Compared with the Gunn dipole domain, there is only an accumulation layer of photon-activated electrons in the photon-activated monopole domain,but no layer of positive ions;Be- cause the electric field formed by the photon-activated monopole domain and the photon-activated holes is the opposite of the exter- nal electric field, the electric field before the monopole domain is enhanced and the electron concentration at the head of the domain is higher than in other regions;a monopole domain can grow until it becomes a luminous domain because of impact ionization,and a luminous domain will evolve into an avalanche luminous domain if it reaches avalanche conditions. Finally,important experimental phenomena of the switch working in nonlinear mode,such as the ultrafast rising edge,luminous current filaments,and the lock-on state of current,are explained by the model of the photon-activated monopole domain.