Abstract
摘要:本子計畫研究兩個主題:一個是電漿子的熱輻射紅外線雷射,另一個是製作高溫操作、多波段量子點/量子環紅外線偵測器:
A. 電漿子熱輻射雷射及其在光合作用減碳及神經生長上的應用 :
我們所發明之室溫可操作的高功率窄頻寬紅外線電漿子發光源主要以週期孔洞金/二氧化矽/金三層結構所製成,藉由上層金屬的週期性結構所形成的表面電漿共振達到窄頻寬的紅外線發射頻譜。本計畫目標是發展一個更高功率、窄頻寬、極化可選擇性波長的紅外線發光源或雷射源。當中間的二氧化矽層是薄的時候,將上層週期孔洞金屬更換為長方形結構的金屬片,擇此結構加熱時會產生兩個侷域型的表面電漿模態,有不同的波長及互相垂直的極化方向。藉由外加極化器的選擇,可以做成可選擇波長的熱輻射紅外線光源。而當增加二氧化矽厚度大於1.1μm時,波導模態會逐漸出現,具有更窄的頻寬。我們將波導結構與電漿子結構堆疊成垂直元件,當波導模態在波導結構中來回反射並進入具有相同共振波長的電漿子結構會被放大,如果適當設計元件將可以產生雷射。
B. 高溫操作、多波段量子點/量子環紅外線偵測器:
量子點與量子環因為本身具有較高的光吸收係數以及可吸收垂直入射光等特性,被視為未來最有潛力的紅外線偵測器。砷化銦/砷化鎵量子點紅外線偵測器的研究日漸成熟,然而現今最難克服的仍舊在於做到接近室溫的操作溫度,雖然可藉由加入像是砷化鋁鎵等三元化合物,利用其較高的能障來阻擋暗電流以及降低漏電流可提高不少操作溫度,但距離真正的室溫操作仍需不少努力。除了利用砷化鋁鎵之外在結構上亦可用砷銻化鎵取代傳統的砷化鎵覆蓋層來減少砷化銦量子點的應力以及形成阻擋層,在製程上面也可做些改善來避免漏電流所造成的影響。本子計畫內容主要是以電漿處理、氧化層覆蓋、邊緣結構縮減等製程技術來減少表面的缺陷或是直接阻擋漏電流的行進路徑。另外也利用周期性結構的表面電漿電場的特性增強垂直方向的吸收,而增加量子效率並且做特定波段或是多波段的選擇。藉由上述方式期望可以降低暗電流提升光電流做出在 3-300μm波段範圍內有高操作溫度及高反應度的量子點/量子環紅外線偵測器。
Abstract: In this project, we plan to study two subjects: first is to develop plasmonic thermal laser. Second is to fabricate High operation temperature and multi-waveband quantum dot/ ring infrared photodetectors:
(A) Plasmonic Thermal Elaser and Its Application to Carbon Dioxide Reduction by Photosynthesis and Growth of Neurons
Room temperature operated narrow-band infrared plasmonic thermal emitter (PTE) invented by our lab has been successfully realized using an Au/SiO2/Au tri-layer structure with periodic holearrays perforated on the top metal layer. The narrow bandwidth infrared emission spectra were obtained by the inteaction of black body radiation from SiO2 laer and theperiodic structure induced surface plasmon (SP) resonance. Our goal is to develop higher power, narrow-band, wavelength selective infrared plasmonic thermal emitter or laser. It was found that as the thickness of SiO2 layer is thin and the top layer was replaced by a rectangular metallic patch. Two localized surface plasmons (LSPs) with different wavelengths and orthogonal polarizations will be induced which can be selected out by an external polarizer. Therefore, a wavelength selective infrared plasmonic thermal emitter can be achieved. As the SiO2 layer thickness exceeded 1.1 m, the waveguide mode appeared in the spectra. We will stack the waveguide and plasmonic structures in a vertical manner.The waveguide mode bounces back and forth in the waveguide and is amplified by the plasmonic structure when it enters the structure with the same plasmon resonant wavelength. This is going to achieve laser action if the device is designed properly.
(B) High operation temperature and multi-wavelength quantum dot/ ring infrared photodetectors
Quantum dots and rings have high absorption coefficients for IR light and can absorb the normal incident light. They are regarded as the potential candidate of the future infrared photodetectors. InAs/GaAs quantum dots/rings infrared photodectors (QDIPs/ QRIPs) have been investigated in recent years. The most difficult problem is how to achieve the room temperature operation. Although, AlxGa1-xAs ternary compound is adopted to be the blocking layer which will block the dark and leakage current to enhance the operation temperature, it is still hard to achieve the room temperature operation for QDIPs/QRIPs. Besides AlxGa1-xAs, GaAs1-xSbx could be used to reduce the stress of quantum dots and could block dark dcurrent due to its band alignment with InAs and GaAs layers. Furthermore, using plasma treatment, oxide passivation, and edge thinning technique in the device fabrication process are another ways to reduce the surface states or block the leakage route which will reduce the dark and leakage current. The metal contact structure perforated by periodic hole arrays could also be adopted to select the particular wavelength range and enhance the quantum efficiency due to its surface plasma effect. Through these process techniques and suitable device structures, it is hoped to fabricate multi- wavelength QDIPs/QRIPs with high operation temperature and high responsivity in the 3 to 300 μm range.
Keyword(s)
熱輻射
熱輻射雷射
表面電漿子
紅外線偵測器
quantum dot/ring infrared photodetectors
surface plasmon