Microscopic mechanisms for creation and removal of metastable dangling bonds in hydrogenated amorphous silicon
Microscopic mechanisms for creation and removal of metastable dangling bonds in hydrogenated amorphous silicon
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氢化非晶硅中亚稳态悬空键产生和去除的微观机制
DOI：
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发表时间：
2002
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通讯作者：
R. Wehrspohn
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作者：
M. J. Powell;S. Deane;R. Wehrspohn
我们提出了氢化非晶硅中亚稳态硅悬键缺陷产生的微观模型，该模型适用于太阳能电池中光致缺陷的产生（Staebler-Wronski 效应）和薄膜晶体管中偏置应力引起的缺陷产生。光或栅极偏压导致电子-空穴对或电子分别定位在短而弱的Si-Si键上，然后断裂。来自相邻双氢化弱 Si-Si 键 (SiHHSi) 的氢原子移动到断裂 Si-Si 键的 ${T}_{d}$ 位点。 SiHHSi 中的另一个 H 原子也位于能量有利的 ${T}_{d}$ 位点。总的来说，该反应产生了两个 SiHD 缺陷。每个 SiHD 缺陷都是紧密的 Si 悬挂键和 Si-H 键，其中 H 原子位于 ${T}_{d}$ 位点，而不是 BC 位点。 ${T}_{d}$ 位点中悬空键与 H 原子之间的距离在 4char21{}5 AA{} 范围内，与 ESR 数据一致。大多数硅悬键（亚稳态和稳定）均以 SiHD 形式存在，其中 H 原子位于 ${T}_{d}$ 位点。缺陷产生的微观过程相当局部化，只需要短程 H 运动，该运动通过相邻 ${T}_{d}$ 位点之间的键转换进行。相比之下，热退火过程中缺陷去除的微观过程涉及 $aensuremath{-}mathrm{S}mathrm{i}:mathrm{H}$ 网络中 H 的重新平衡，并且是一个涉及大部分 H 原子的全局过程。该过程的限速步骤是 Si-H 键从 SiHHSi 位点断裂，其最大活化能为 1.5 eV。我们根据这一过程提出了修订后的氢态密度图。
We present a microscopic model for metastable Si dangling-bond defect creation in hydrogenated amorphous silicon, which is applicable to both light-induced defect creation in solar cells (Staebler-Wronski effect) and bias-stress-induced defect creation in thin-film transistors. Light or gate bias causes electron-hole pairs or electrons, respectively, to be localized on short, weak Si-Si bonds, which then break. A hydrogen atom, from a neighboring, doubly hydrogenated weak Si-Si bond (SiHHSi) moves to the ${T}_{d}$ site of the broken Si-Si bond. The other H atom from the SiHHSi is also located in the energetically favorable ${T}_{d}$ site. Overall, the reaction produces two SiHD defects. Each SiHD defect is an intimate Si dangling bond and Si-H bond, where the H atom is in the ${T}_{d}$ site, not the BC site. The distance between the dangling bond and the H atom in the ${T}_{d}$ site is in the range 4char21{}5 AA{}, in agreement with ESR data. The majority of silicon dangling bonds, both metastable and stable, exist as SiHD, with the H atom in the ${T}_{d}$ site. The microscopic process for defect creation is fairly well localized, requiring only short-range H motion, which proceeds via bond switching between neighboring ${T}_{d}$ sites. In contrast, the microscopic process for defect removal during thermal annealing involves reequilibration of H in the $aensuremath{-}mathrm{S}mathrm{i}:mathrm{H}$ network and is a global process involving a large fraction of H atoms. The rate-limiting step for this process is Si-H bond breaking from SiHHSi sites, which accounts for the maximum activation energy of 1.5 eV. We present a revised hydrogen density of states diagram, in line with this process.