具矽量子點超晶格結構之光伏特及光偵測元件

Abstract

本論文報告雙極的MOS結構增益型光偵測器的光響應情形，此結構是利用埋藏矽量子點的奈米孔洞二氧化矽層作為包覆層。此元件電流放大機制類似於傳統的光電晶體:載子由射極(即元件反轉層)注入到集極。而殘留於MS層中的電洞進一步吸引電子由反轉層注入至氧化銦錫電極，因而造成光激電流被放大之效應。利用此原理我們製作含矽量子點閘集層的三極光電場效應電晶體(MOSFET)，在光照的情形下，因為Si-O能階的產生造成殘留於MS的電洞吸引電子因此在通道上形成較大的飽和電壓和汲集電流，我們也觀察到光響應增益的現象。 具奈米孔洞之二氧化矽介電質，擁有低的介電常數，該材料具有的孔洞特性也是其具有低折射率的主要原因。與Si3N4薄膜一同應用於漸變折射率之雙層抗反射層之矽太陽能電池，對於太陽光穿透率的改善，使得矽太陽能電池轉換效率將有4%的提升。我們也提出在奈米孔洞之二氧化矽薄膜中填入量子點的方式加入光伏電池中提供波長轉換及電荷直接分離，結果觀察到造成光電壓增益的現象。

We reported enhanced spectral photoresponse from a two-terminal metal-oxide-silicon (MOS) type detector with a capping layer of Si-QDs embedded MS and the enhancement is attributed to transistor-like operation of the device, in which the inversion layer acts as the emitter while trapping of positive charges in the mesoporous dielectric layer assists the carrier injection from the inversion layer to the contact, resulting in current amplification. The photo state of Si-O nanostructures in transistors dominates threshold voltage and, therefore, large drain currents. Hence, a three-terminal photo-metal-oxide-silicon field-effect transistor (MOSFET) with a Si-O nanostructured gate dielectric will be developed to enhance photoresponse. Mesoporus silica (MS) dielectrics revealed low dielectric constant, the porosity in such materials was also responsible for refractive index as low as 1.25, integrated together with Si3N4 layers to be double-layer-based graded-refractive-index ant-reflectors for silicon solar-cells. Enhanced solar-light transmission increased conversion efficiency of Si solar panels by 4%. We will also introduction of Si-QDs embedded MS in PV cells can provide wavelength down conversion, and direct charge separation to produce an enhanced photovoltaic. ii