Persistent photoconductivity (PPC) effect and its light-intensity dependence of both enhancement and depletion (E-/D-) mode amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) are systematically investigated. Density of oxygen vacancy (V_O) defects of E-mode TFTs is relatively small, in which formation of the photo-induced metastable defects is thermally activated, and the activation energy (E _a) decreases continuously with increasing light-intensity. Density of V_O defects of D-mode TFTs is much larger, in which the formation of photo-induced metastable defects is found to be spontaneous instead of thermally activated. Furthermore, for the first time it is found that a threshold dose of light-exposure is required to form fully developed photo-induced metastable defects. Under low light-exposure below the threshold, only a low PPC barrier is formed and the PPC recovery is fast. With increasing the light-exposure to the threshold, the lattice relaxation of metal cations adjacent to the doubly ionized oxygen vacancies () is fully developed, and the PPC barrier increases to ∼ 0.25 eV, which remains basically unchanged under higher light-exposure. Based on the density of V_O defects in the channel and the condition of light illumination, a unified model of formation of photo-induced metastable defects in a-IGZO TFTs is proposed to explain the experimental observations.

系统地研究了持久光电导 (PPC) 效应及其对增强和耗尽 (E-/D-) 模式非晶 InGaZnO (a-IGZO) 薄膜晶体管 (TFT) 的光强度依赖性。E型TFT的氧空位(V _O )缺陷密度相对较小，其中光致亚稳态缺陷的形成是热激活的，激活能( E _a )随着光强的增加而不断降低。_{V O}的密度D模式TFT的缺陷要大得多，其中发现光致亚稳态缺陷的形成是自发的，而不是热激活的。此外，首次发现需要阈值剂量的曝光来形成完全发展的光诱导亚稳态缺陷。在低于阈值的低光照下，仅形成低PPC屏障，PPC恢复快。随着曝光量增加到阈值，与双电离氧空位（）相邻的金属阳离子的晶格弛豫充分发展，PPC势垒增加到~0.25 eV，在更高的曝光量下基本保持不变。基于VO的_密度在沟道缺陷和光照条件下，提出了一个统一的a-IGZO TFT中光致亚稳态缺陷形成模型来解释实验观察结果。