非晶矽薄膜電晶體作為光感測元件及電路之研究(II)

Abstract

在顯示面板上加入光感測功能，可增加其附加價值，是重要的應用需 求。然而，大部分傳統型的光感測器都是用外部的分離元件去裝置的，所 以會造成額外的成本與設計上的複雜度。非晶矽薄膜電晶體由於本身便具 有光感測特性以及較易製作於大面積上，在主動矩陣液晶顯示器以及偵測 器上受到廣泛的注意。目前已有許多使用薄膜電晶體的感測機構被發表討 論。 在本計畫中，將延續第一年的成果，增加電晶體對光感測的動態偵測 範圍，並且使其較不光電流劣化的影響。我們使用不同類型的薄膜電晶體 元件設計多種光感測電路，藉由不同結構亦或閘極電壓的調整，我們可以 依照需求決定光產生電流的效率區域多寡。因此，所設計的光感測電路可 在不同區域操作下不同的光偵測能力，在動態偵測範圍中提升訊號雜訊的 比值。此外，此系統的特殊設計結構亦可用作偵測背光源。 由於整個方法的製程與習知的相同，並沒有額外的特殊製程，易於將 光感測器整合到面板上，在接近既有成本的情況下，使面板產品更具競爭 力。

To make a value-added display, it is expected to embed light sensors on the display panel. However, most of the conventional ambient light sensor systems were implemented by external discrete devices which cause additional cost and the design complexity. Hydrogenated amorphous silicon thin film transistors (a-Si:H TFTs) are extensively heeded in the application of active matrix liquid crystal display (LCD) and sensors due to their photo sensitivity and ease of fabrication across large area substrates. Some sensing functions using TFTs have been already demonstrated. In this project, we will base on the results of the first year to increase the dynamic range of photo sensing using TFTs and be immune to photocurrent degradation. We will design sensing circuit using different types of TFT device. We can design the depletion length to control the effective region of photo-excited current from adjustment of different types of device structure or gate voltages. Therefore, the designed sensing circuits can adapt to the wide dynamic range from the dark to the bright with different sensitivities to increase signal-to-noise ratio (SNR). Furthermore, the system also can be used to sense back light illumination. This method is based on the conventional process and thus does not need novel device process development. It can be implemented easily on to the panel and make the product be more competitive at similar cost.