紫外光在非晶矽薄膜電晶體特性影響之研究

Abstract

本論文首度研究非晶矽薄膜電晶體經紫外光照射後電性變化的物理機制， 包括陷阱的狀態、 濃度以及載子復合產生速率。 為了使分析的元件特性更符合實際現象， 模擬上， 非晶矽層中陷阱的分佈與濃度耦合於泊松方程式；而載子復合產生速率則耦合於電子/電洞 連續方程式， 以及晶格熱流方程式。 此反轉堆疊式非晶矽薄膜電晶體模擬的電流電壓曲線在不同的紫外光照射次數大小皆配合量測實驗被仔細校估過。 主要的電性結果顯示， 在紫外光照射後， 主要有三個現象產生， 即臨限電壓的增加、 漏電流的下降以及驅動電流的下降。 隨著紫外光照射次數增加， 非晶矽層中陷阱增加。 這會使有效穿遂電子質量增加以及費米能階降低。 此研究提供了光照射後的影響及機制之模型化以改善非晶矽薄膜電晶體之開關特性。

In this study, the physical mechanisms of UV illumination for a-Si:H TFTs including the state and density of traps are for the first time studied and calibrated. To characterize and optimize the characteristics of devices, Poisson, electron/hole continuity, and lattice heat flow equations are solved coupling with density and distribution of trap states in the a-Si:H layers. The I-V characteristics of the inverted staggered a-Si:H TFTs with different magnitude of UV light illumination is calculated and calibrated with experimental measurements. The preliminary result shows that the traps states in the a-Si:H layer alter the effective mass of electrons and the movement of Fermi level after UV illumination. This study provides an insight into the impact of photo-illumination and the mechanism for device modeling to improve the switching characteristics of amorphous silicon thin-film transistors.