Dual-Level Enhanced Nonradiative Carrier Recombination in Wide-Gap Semiconductors: The Case of Oxygen Vacancy in SiO₂

Abstract

The conventional single-defect-mediated Shockley−Read−Hall model suggests that the nonradiative carrier recombination rate in wide-band gap (WBG) semiconductors would be negligible because the single-defect level is expected to be either far from valence-band-maximum (VBM) or conduction-band-minimum (CBM), or both. However, this model falls short of elucidating the substantial nonradiative recombination phenomena often observed experimentally across various WBG semiconductors. Owing to more localized nature of defect states inherent to WBG semiconductors, when the defect charge state changes, there is a pronounced structural relaxation around the local defect site. This suggests that a defect at each charge state may exhibit a few distinct local configurations, namely, a stable configuration and a few metastable/transit state configurations. Consequently, a dual-level nonradiative recombination model should more realistically exist in WBG semiconductors. In this model, through the dual-level mechanism, electron and hole trap levels are different from each other and could be closer to the CBM for the electron trap and closer to the VBM for the hole trap, respectively; therefore, this significantly increases the corresponding electron and hole capture rates, enhancing the overall process of nonradiative recombination, and explains the experimental observations. In this work, taking technically important SiO 2 as an illustrative example, we introduce the dual-level mechanism to elucidate the mechanism of nonradiative carrier recombination in WBG semiconductors. Our findings demonstrated strong alignment with available experimental data, reinforcing the robustness of our proposed dual-level model. Our fundamental understanding, therefore, provides a clear physical picture of the issue and can also be applied to predict the defect-related nonradiative carrier recombination characteristics in other WBG materials.

Gamma-Ray Irradiation Induced Dielectric Loss of SiO2/Si Heterostructures in Through-Silicon Vias (TSVs) by Forming Border Traps

“…The relation between the BT and the AC irradiation effect can be made clearer by considering the microscopic mechanism, which is proposed in the following according to the first-principles studies in refs − . Figure illustrates the microscopic structures corresponding to the BT/OT.…”

“…After irradiation with a low gamma-ray dose, a large amount of neutral V Oδ is transformed to the metastable E’ δ by capturing a hole and breaking the Si–Si bond. E′ δ can transform to the more stable E′ γ with a puckered structure by overcoming a very small barrier, but this transformation does not happen immediately as one can observe the EPR signal of E′ δ . , Gamma-ray irradiation can accelerate this transformation by providing the energy for overcoming the barrier. E′ δ and E′ γ are more polarizable than V Oδ considering that the shape of the electron cloud can change more freely without the Si–Si bond.…”