複晶矽薄膜電晶體之光特性研究

Abstract

在此論文裡，我們將分為兩個主題，第一個主題針對光漏電機制做探討，第二個主題是對具有橫向身體端的薄膜電晶體元件做光特性方面的研究。在第一個主題部分，從文獻中可以瞭解光漏電與通道底部及主動層厚度有關，因此我們對元件的通道做摻雜處理，試圖抑制光漏電。照光後的電子電洞對會有部分被我們創造的複合中心所捕獲，而使到達源極與汲極端的電子電洞對減少而降低光漏電流。經由不同深度的通道摻雜，我們發現摻雜於通道底部對抑制光漏電最為有效。我們並且改變主動層的厚度，對於有無通道底部摻雜的元件做進一步的研究。 在第二個主題部分，我們設計了不同尺寸不同身體端位置的薄膜電晶體元件，並對於元件做基本特性的量測，而確定了身體端收集到的電流是來自衝擊離子效應所產生的電洞。而在照光實驗中，發現了具有身體端的薄膜電晶體元件可以偵測光電流，因此對光特性方面做進一步的研究。對於量測的結果，我們提出了能帶圖來解釋其電性。

In this thesis, we investigate two subjects. First is the study on the mechanism of photo leakage current. Secondly, the study on photo characteristics of polycrystalline silicon Thin-Film Transistors with lateral body terminal (LBT TFTs). In first subject, we implanted the channel of TFTs in order to reduce the photo leakage current. From reference, the photo leakage current is dependent on the channel and the thickness of active layer. The part of electron-hole pairs which generate by backlight could recombine by the trap which we create. The photo current becomes lower because both the electrons which reach the drain terminal and the holes which reach the source terminal become lower. By different depth of channel implanted, we could observe the TFTs with implanted the bottom of channel have least photo current. Then we change the thickness of active layer in order to research further. In second subject, we designed the LBT TFTs with varied LBT position and size. We measured the device characteristics. The body current comes from the holes which generate by impact ionization. In light experiment, we found the LBT TFTs could sense light. So we measured the LBT poly-Si TFTs in dark and irradiated illuminance to analyze the device behavior. We thought that the device behavior is come from the L shape p/i/n in LBT TFT. In LBT TFT, source and drain is n+ region, channel is intrinsic region, and LBT is p+ region. In order to explain the device behavior, the energy band of the p/i/n in LBT TFTs is proposed.