半導體奈米材料於新穎光電元件之設計、製作及特性

Design, Fabrication and Characterization of Novel Optoelectronic Devices Based on Semiconductor Nanomaterials

海德(Haider, Golam)

指導教授 ： 陳永芳 ； 陳福榮

國立清華大學/原子科學院/工程與系統科學系/博士(2017年)

摘要

為了克服能源危機、全球暖化、環境汙染等全球性的困難與挑戰，高性能光電元件的發展將電子與光電產業的領域趨勢提升下一個階段，這些光電元件的發展與突破也相對帶來了對新功能和應用的巨大需求。目前對高性能光電元件的突破已取得了不少進步，但對創造出商業的影響潛力仍需要許多努力，經由對多種材料組成的混合奈米結構做出適當的設計，可以得到擁有獨一無二的特性以及多功能性的元件，而這樣的突破是無法從單一材料組成元件中取得的。本篇論文的目的是致力於設計由多種材料組成的新穎光電元件，這些設計能夠應對上述種種全球性的挑戰，同時也在高性能光電元件的發展中踏出重要的一步。這些結果在本篇論文中被歸類為幾個子標題，並於以下總結。

光偵測器: 衍生於石磨烯和石墨烯量子點之透過電極化誘發的超高響應光偵測器

　　在光傳輸系統中，光偵測器佔據重要的地位，在日常生活中也被廣泛應用，已經有很多人投入許多心力，致力於發展靈敏度高、反應速度快、微型化、低成本且對環境友善的光偵測器。在這一章中，我們將展示藉由高吸收率且取自於植物的石墨烯量子點（GQDs）、高導電率石磨烯以及永久極化壓電材料基板的整合，設計出能夠克服許多上述限制的光偵測器。在壓電基板給的電場作用下，石墨烯量子點中光生成的電荷會更傾向轉移到導電的石磨烯層上，這樣的設計元件，其光反應比起目前所知的光偵測器，能夠被增強至超過１００倍，此外反應時間會縮短十倍。這個方法能夠輕鬆調控取自於植物的石墨烯量子點的特性，因此我們預期可由此設計，進一步發展出高靈敏度和寬光頻反應的綠色偵測器。

發光二極管（LED）：在固有的金屬-有機結構中使用電驅動產生白光

由於其低功耗和更長的使用壽命，發光二極管（LED）已經成為傳統照明的替代品。時至今日，一般的白光LED（WLED）取決於含有稀土元素的磷光體的光子下轉換，這限制了其使用狀況，也提高了製造成本。考量到了環境問題，也為了避免過多能源的浪費，發展出直接WLED是必須，也是非常有挑戰性的事情。為了避免在製造一般WLED出現的困難，在這份報告中，我們設計並展示了由鍶基金屬有機結構{[Sr(ntca)(H2O)2]·H2O}n (1) 、石墨烯和無機半導體，可以產生明亮的白光。我們能成功實現電驅動白光LED，不只是因為合適的MOF結構設計，更是因為對於材料的正確使用，像是應用了石墨烯的獨特性質和MOF及半導體層之間恰當的能帶排列。因為將MOF作為活性材料的電致發光是非常罕見且有趣的，而且直接WLED也不常見，所以我們在這裡的成果對於固態照明領域的發展是非常有意義的。

石墨烯基光電元件：衍生於石墨烯基異質接面之狄拉克點所誘發的超低閥值雷射行為及巨大光電量子震盪

存在於狄拉克點附近有效質量為零的電子，被預期為科學研究及科技應用創造嶄新的典範，然而其相關發現卻相當有限。因此在本文中，我們研發了一個簡易三明治堆疊結構，將石墨烯量子點（GQDs）包覆於兩層石墨烯之中，此結構展現了許多前所未有的特點，包含：狄拉克點所誘發的超低閥值雷射行為、具有超窄頻譜負阻效應（NDR）的巨大峰谷比（PVR）以及電流跟發光強度的量子震盪行為。特別是只有12.4 nA/cm2的閾值是所有已報導電驅動雷射種類中的最低值，且超過100的波谷比值比起其他已報導的石墨烯基元件創下了最高紀錄。我們展示了所有這些新的現象，皆可以利用石墨烯量子點和石墨烯能帶結構的獨特性以及共振量子穿遂來得到良好的解釋。我們的發現不只可以擴展到其他奈米結構系統，還為了高效率發光二極體、雷射以及其他尚未實現之奈米電子應用的發展帶來一條嶄新的道路。

白光隨機雷射：一個具有高效率的白光隨機雷射之元件

多波長可見光雷射晶片擁有許多應用，像是超高亮度的固態照明，全彩顯示器，光通訊以及生物影像。然而，多波長可見光雷射晶片的研究上遇到許多挑戰，不管是材料需求又或是過於複雜的設計。在這篇文章裡，我們結合NaYF4:Yb/Er/Tm@NaYF4:Eu殼結構復合納米粒子以及Au/MoO3 超穎材料研發出設計簡單全溶液製成的高效率單晶白光隨機雷射模組。多波長的雷射光涵蓋紅色、綠色、以及藍色，可以大幅度的被特別設計超穎材料內高動量的波增強以及減少光子傳遞的損耗能量。藉由這樣的機制，上轉換的雷射光強可以大幅度增強50倍，以及雷射閾值會大幅度的下降。另外，不規則介質內自然產生的多重散射可以提供一個簡易的封閉回饋路徑讓高同調性的隨機雷射產生。實驗的結果同時也吻合模擬的預測 這樣簡單的設計不僅僅可以調變雷射顏色，還可以延伸到許多不同的材料上。再加上隨機雷射獨有的多方向雷射光束，我們的元件對於未來許多雷射的實際應用提供一個可靠的解決方案。

關鍵字

奈米材料 ； 奈米材料 ； 光電元件 ； 光偵測計 ； 發光二極體 ； 雷射元件 ； 白光隨機雷射 ； 石墨烯 ； 鐵電材料 ； 金屬有機框架材料 ； 雙曲超穎材料 ； 上轉換奈米粒子

並列摘要

Electronic and optoelectronic industries are going through a major paradigm shift for the development of high performance optoelectronic devices to circumvent the global challenges such as, global energy crisis, global warming, environmental toxicity etc. These developments create a huge demand for new functionalities and applications. Progress has been made, but efforts to create a substantial commercial impact still remain. Hybrid nano composites consist of multi component materials with appropriate design can give rise unique properties and multi-functionalities which cannot be seen in a single component material. The objective of this thesis is devoted to design novel optoelectronic devices based on multicomponent materials that can address the global challenges creating an environmental footprint of high performance optoelectronic devices. The results are classified in to several sub-topics, which can be summarized as follows.

Photodetector: Electrical Polarization Induced Ultra-high Responsivity Photodetectors Based on Graphene and Graphene Quantum Dots

Photodetector is a critical component in optical communication system that is omnipresent in our daily life. Great efforts have been devoted to the development of environmental-friendly photodetectors with high sensitivity, fast response, miniaturization and low cost. In this chapter, we show that many of these limitations can be overcome by integrating the high absorption efficiency of graphene quantum dot (GQD) produced from plants, the high conductivity of graphene, and the permanent polarization of piezoelectric substrate. With the assistance of the electric field provided by the piezoelectric substrate, the photogenerated charges in the GQD can be preferably transferred to the conductive graphene layer. It is found that the photoresponsivity of the device can be enhanced by more than 100 times and the response time is 10 times faster than the current photodetectors. With the ease of tunable properties of GQDs and their availability from plants, we expect our approach will contribute to the further development of green photodetectors with high sensitivity and wide spectral response.

Light Emitting Diode (LED): Electrically Driven White Light Emission from Intrinsic Metal–Organic Framework

Light emitting diodes (LEDs) have drawn tremendous potential as a replacement of traditional lighting owing to its low power consumption and longer lifetime. Nowadays, the practical white light LEDs (WLED) are contingent on the photon down conversion of phosphors containing rare-earth elements, which limits its utility, energy and cost efficiency. In order to resolve the energy crisis and to address the environmental concerns, designing a direct WLED is highly desirable and remains a challenging issue. To circumvent the existing difficulties, in this report, we have designed and demonstrated a direct WLED consisting of a strontium-based metal-organic framework, {[Sr(ntca)(H2O)2]·H2O}n (1), graphene and inorganic semiconductors, which can generate a bright white light emission. In addition to the suitable design of a MOF structure, the demonstration of electrically driven white light emission based on a MOF is made possible by the combination of several factors including the unique properties of graphene and the appropriate band alignment between the MOF and semiconductor layer. Because electroluminescence using a MOF as an active material is very rare and intriguing and a direct WLED is also not commonly seen, our work here therefore represents a major discovery which should be very useful and timely for the development of solid state lighting.

All Graphene Based Optoelectronic Device: Dirac-point Induced Ultralow-threshold Laser Action and Giant Optoelectronic Quantum Oscillations Derived from all Graphene Based Heterojunctions

The occurrence of zero effective mass of electrons at the vicinity of the Dirac-point is expected to create new paradigms for scientific research and technological applications, but the related discoveries are rather limited. Here, we demonstrate that a simple architecture composed of graphene quantum dots (GQDs) sandwiched by two graphene layers can exhibit several unprecedented features, including the Dirac-point induced ultralow-threshold laser action, giant peak-to-valley ratio (PVR) with ultra-narrow spectra of negative differential resistance (NDR) and quantum oscillations of current as well as light emission intensity. In particular, the threshold of only 12.4 nA/cm2 is the lowest value ever reported in all kinds of electrically driven lasers, and the PVR value of more than 100 also sets the highest record compared with all reports on graphene based devices. We show that all these new phenomena can be interpreted well based on the unique properties of the band structure of GQD and graphene as well as resonant quantum tunneling. Our findings can be extended to other nano-structural systems and open a route for the development of highly efficient light emitting diodes, lasers and many not-yet-realized nano-electronic applications.

A Highly Efficient Single Segment White Random Laser

Production of multi-color or multiple wavelength lasers over the full visible-color spectrum from a single chip device has widespread applications, such as super-bright solid state lighting, color laser displays, light based version of Wi-Fi (Li-Fi), and bio-imaging etc. However, designing such lasing devices remains a challenging issue owing to the material requirements for producing multi-color emissions and sophisticated design for producing laser action. Here we demonstrate a simply design and highly-efficient single segment white random laser based on solution processed NaYF4:Yb/Er/Tm@NaYF4:Eu core-shell nanoparticles assisted by Au/MoO3 multilayer hyperbolic metamaterials. The multi-color lasing emitted from core-shell nanoparticles covering the red, green, and blue, simultaneously, can be greatly enhanced by the high-k modes with a suitable design of hyperbolic metamaterials, which enables to decrease the energy consumption of photon propagation. As a result, the energy upconversion emission is enhanced by ~ 50 times with a drastic reduction of lasing threshold. The multiple scatterings arising from the inherent nature of the disordered nanoparticle matrix provide a convenient way for the formation of closed feedback loops, which is beneficial for the coherent laser action. The experimental results were supported by the electromagnetic simulations derived from the finite-difference time-domain (FDTD) method. The approach shown here can greatly simplify the design of laser structures with color-tunable emissions, which can be extended to many other material systems. Together with the characteristics of angle free laser action, our device provides a promising solution towards the realization of many laser-based practical applications.

並列關鍵字

Nanomaterials ； Nanomaterials ； Optoelectronic Devices ； Photodetector ； Light Emitting Diodes ； Laser Devices ； White Random Laser ； Graphene ； Ferroelectric Materials ； Metal-Organic Frameworks ； Hyperbolic Metamaterials ； Upconversion Nanoparticles

參考文獻

67. Hsieh, Y. -P.; Hofmann, M.; Chang, K. -W.; Jhu, J. G.; Li, Y. -Y.; Chen, K.Y.; Yang, C. -C.; Chang, W. -S.; Chen, L. -C. Complete Corrosion Inhibition through Graphene Defect Passivation. ACS Nano, 8, 443-448 (2014).

56. Johnson, J. C., Choi, H. –J., Knutsen, K. P., Schaller, R. D., Yang, P., Saykally, R. J. Single gallium nitride nanowire lasers. Nat. Mater. 1, 106-110 (2002).

Chapter 1

1. Sharma, N., Ojha, H., Bharadwaj, A., Pathak, D. P., Sharma, R. K. Preparation and catalytic applications of nanomaterials: a review. RSC Adv., 5, 53381-53403 (2015).

3. Lu, W., Lieber, C. M. Nanoelectronics from the bottom up. Nat. Mater., 6, 841-850 (2007).