本研究是利用水熱法成長一維氧化鋅奈米線，以氧化鋅奈米線為基材搭配其它P型半導體材料，以形成奈米異質接面結構，藉由奈米線異質接面一維結構之量子侷限效應，提升元件之光電響應能力。本研究方法具有低溫低壓製程、製程時間短和元件製作成本低廉，可以免除傳統半導體製程所需之設備費用高昂，製程技術複雜耗時，致使元件成本偏高。
本實驗製備出n-ZnO nanowires/p-NiO與n-ZnO nanowires/p-GaN之奈米異質異質接面結構，將此兩種結構應用於紫外光感測器和太陽電池元件上。n-ZnO nanowires/p-NiO之奈米異質接面結構其主要特徵在於先行於ITO玻璃基板上，利用HTG成長氧化鋅奈米線(ZnO-NWs)，再將氧化鎳(NiO)沉積於ZnO-NWs 表層上，則可得奈米線異質接面結構。此元件特性當電壓在順向電壓為5 V時之電流(Iforward)和逆向電壓為-5 V時之電流(Ireverse)下，具有很好的整流比(Iforward/Ireverse＝89)。在紫外光照射下當NiO厚度為100 nm時，在-5 V時具有最佳之光電流特性，光電流約為6 A/cm2，所增加之電流約為暗電流之8倍。此元件更具有很快速的光響應時間，其上升時間(rise time)和下降時間(fall time)約為4秒和13秒。
於n-ZnO nanowires/p-GaN之異質結構太陽電池方面，藉由其奈米線之異質接面一維結構之量子侷限效應，以提升光電轉換效率，另一方面由於奈米線有效提升表面之粗糙度，可大量降低光線的反射，增加電子、電洞的產生。由實驗中可得知當水熱法成長氧化鋅奈米線的成長時間為1 hr時，可以得較佳之光電轉換效率(2.28%)。此異質接面結構不僅可應用在太陽電池上面，當照射紫外光時，此元件亦會產生光電流特性，所以也可將此元件應用在紫外光感測器上。相信只要適度的調變其成長參數，預期n-ZnO nanowires/p-GaN之奈米異質接面結構應用於太陽電池、光感測器等光電元件上將會有極大的發展潛力。

In this thesis, the growth and optoelectronic properties of ZnO nanowires-based nanoheterojunction structures are studied. A novel technology using hydrothermal growth (HTG) associated with deposition techniques for the fabrication of nano hetero structure based on ZnO nanowires (ZnO-NWs) is reported in this study. In addition, this study also proposes the use of ZnO-NWs-based nanoheterojunction structures for potential in applications of nano electronic and optoelectronic devices.
First, nanoheterojnuction structures were formed via e-beam deposition of p-type nickel oxide (NiO) onto the vertical-aligned ZnO-NWs grown by HTG method. The dark J-V curve shows that the prepared NiO/ZnO-NWs nanoheterojunction structure with 100 nm-thick NiO film has a diode-like behavior with a forward threshold voltage (Vth) of 5.9 V, a leakage current (Jr at -5V) of 0.64 A/cm2, and a good rectification ratio (Iforward/Ireverse at 5 V) of 89, respectively. The experimental optoelectronic characteristics reveals that the one-dimension NiO/ ZnO-NWs nanoheterojunction structures have fairly good sensitivities and fast responses (the rise time and fall time is about 4 and 13 sec, respectively) to UV light with an increase in the photocurrent of about 8.
Furthermore, in order to improve the optoelectronic properties of the nanoheterojunction structures, the growth of ZnO-NWs with controllable diameter/length/density and fabrication of ZnO-NWs-based nanoheterojunction structures on p-type gallium nitride (p-GaN) are presented. The optoelectronic properties of the ZnO-nanowires/p-GaN nanoheterojunction structures with good UV sensitivities and superior PV performances under an UV light and a simulated AM1.5G solar illumination are reported. Under AM 1.5G solar light illumination, the prepared ZnO-NWs/p-GaN nanoheterojunction structures show superior photovoltaic performances. The short-circuit current, open-circuit voltage, fill factor and power conversion efficiency of the ZnO-nanowires/p-GaN nanoheterojunction structures with 1.2-m-long and 100-nm-diameter ZnO-nanowires are 3.43 mA/cm2, 1.7 V, 39.13%, and 2.28%, respectively. It is expected that the functional ZnO-NWs-based nanoheterojunction structures would offer a simple and low-cost building block for high-performance optoelectronics in the future.

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