同心圓金氧半穿隧二極體耦合效應在光傳感中的應用

Abstract

本篇論文主要探討同心圓金氧半穿隧二極體兩鄰近電極間的耦合效應以及耦合效應在光感測方面的影響及其應用。我們探討了一般元件以及去除邊緣氧化層之元件的特性差異，並利用短路電流量測證明耦合效應的存在，也觀察到在不同的閘極偏壓下，有不同的耦合效應機制，對元件電流造成的變化也不同。在累積區的耦合效應是由電子濃度梯度形成的擴散電流主導，而在深空乏區為邊緣電場所造成的電流來主導。其中，去除邊緣氧化物的元件在深空乏區由於邊緣電場分布較窄而缺乏耦合效應。 另外，以量測短路電流作為光感測的參數可以保持較好的線性度為動機，將內圓閘極施加正偏壓，一般元件的外環短路電流可以線性地隨著光強度增加由負增加到正，這種利用耦合效應由負切換到正的現象對於光感測辨識的靈敏度是很大的優勢；至於去除邊緣氧化層的元件，我們發現量測基板電流可以得到暗電流以內圓電流為主導、光電流以外環電流為主導的高光暗電流比。最後，除了短路電流量測，還提出了將基板浮動的特殊操作，藉由這種方式得到在正偏壓下以及負偏壓下都可以操作的光感測方式。相信本篇論文的分析對於光感測發展有其重要性。

This thesis explores the coupling effect between two neighboring electrodes of the concentric MIS(p) tunnel diode and its impact on photo sensing. Specifically, we dis-cuss the differences between general devices and devices with edge-removed oxide and demonstrate the existence of the coupling effect through short-circuit current. The coupling effect is dominated by distinct mechanisms in different regions. In the accu-mulation region, the diffusion current formed by the electron concentration gradient is the dominant mechanism, while in the deep depletion region, the fringe field domi-nates. However, devices with edge-removed oxide lack coupling effects in the deep depletion region due to the narrower fringing field distribution. In addition, using short-circuit current as the photo sensing parameter can main-tain good linearity. By applying a positive bias to the inner gate, the short-circuit cur-rent of a general outer ring device increases linearly from negative to positive with increasing light intensity. This variable current polarity due to coupling effects pro-vides a notable sensitivity advantage. As for the devices with edge-removed oxide, measuring the substrate current can obtain a higher light-to-dark current ratio, because the photocurrent is dominated by the outer ring, and the dark current is dominated by the inner center. Additionally, we perform a special operation of substrate floating that enables our photo sensing can operate under both positive and negative bias voltages. It is believed that the analysis of this thesis has important implications for the devel-opment of photo sensing.