本論文主要探討利用超音波噴霧熱裂解法沉積法製備氧化鋅鎵應用於紫外光檢測器。超音波噴霧熱裂解沉積法是一種成本低廉、非真空、製成時間短且易於調變前驅物內容物濃度之薄膜沉積技術。我們將該技術應用於紫外光檢測器上製作金屬-半導體-金屬( MSM )以及PN光電二極體結構。
我們分別研究在氧氣及氮氣中以700°C、800°C及900°C中退火一個小時，並得出氧化鋅鎵的最佳退火溫度為800°C，此時能夠有最好的光檢測表現，其中在氮氣或氧氣中退火的元件有著不同特性，以氧氣退火的整體光暗電流都下降，但在偏壓5 V下及照光波長250 nm (UVC)仍然有著不錯的響應度2.10 A/W並且有著較低的響應時間，分別為tr =12.33 s, tf = 0.33 s；以氮氣退火的整體光暗電流都提升，也讓光響應度(Responsivity)在偏壓5 V及照光波長250 nm (UVC)的狀況下高達63.96 A/W，但相對響應時間較高，分別為tr = 23.82 s , tr = 0.88 s ，而在氧氣退火的有著優異的暗電流大約在1.0E-12 A擺盪；氮氣退火則在1.0E-10 A。而兩者(退火氧氣/氮氣)在我們所關注的對深紫外光波段(UVC band)的高選擇率(Selectivity)以RUVC/UVA的計算下之間響應度差距分別達到7 × 10^4及6 × 10^2，表現出很好的對於深紫外光(UVC)的選擇性。
接著我們以此為基礎，繼續以濺鍍法(RF-sputter)成長氧化鎳作為光電二極體(Photodiode)的P型薄膜材料，成功利用P-N結面的內建電場特性，使得退火氧氣及氮氣的元件暗電流更進一步的下降分別達1.0E-13及1.0E-12的等級，並且額外使得響應時間在tr / tf 更進一步降低至2.10 s / 0.36 s ; 11.24 s/ 0.73 s。
為了瞭解氧化鋅鎵薄膜之薄膜厚度、化學組成、結晶性、結晶方向、氧空缺、折射係數、衰減係數及材料能隙，在本研究中使用（一）掃描式電子顯微鏡、（二）穿透式電子顯微鏡、（三）X-射線繞射分析、（四）元素成分分析儀、（五）X-射線光電子能譜儀及（六）橢圓偏振分析儀。我們使用掃描式及穿透式電子顯微鏡拍攝樣品的剖面圖以確認元件薄膜厚度。 並且藉由X-射線繞射分析出我們的氧化鋅鎵薄膜確實有著結晶特性。接著藉由元素成分分析儀進一步分析出薄膜的縱深元素比例極為接近氧化鋅鎵原子比。以此我們在額外以X-射線光電子能譜儀分析存在於薄膜中之氧空缺比例變化，可以證實在不同退火環境下所得到的氧空缺比例所致的導電性差別。最後，我們以橢圓偏振儀獲取的衰減係數及折射率數據能夠計算出氧化鋅鎵有著寬能隙達5 eV，證實此材料對於深紫外光波段的檢測能力。
在本論文中，我們以超音波噴霧熱裂解沉積法製備的氧化鋅鎵深紫外光檢測器相對於其他沉積方法而言，具有低成本且製程快速的優點，接著藉由單純的退火控制，就能夠製造出結晶的氧化鋅鎵。因此，我們認為超音波噴霧熱裂解沉積法在工業的應用上極具優勢與潛力。

This thesis mainly investigates on the zinc gallium oxide-based deep ultraviolet (UV) photodetectors (PDs) by ultrasonic spray pyrolysis deposition. Ultrasonic Spray Pyrolysis Deposition (USPD) is a thin film deposition technology which is low cost, non-vacuum, rapid process and easy to carry out precursor doping, is used to fabricate the zinc gallium oxide active layer. In the thesis, this technique is applied to metal-semiconductor-metal (MSM) and P-N Photodiode.
In the thesis, we firstly investigate the different annealing temperature (Tann) in O2 and N2 for an hour and obtained that the devices annealing at Tann = 800°C performed the best photo detection. Though, both The Idark and Iphoto for the device annealing in O2 lower than without annealing, the Responsivity reaches 2.10 A/W @5V illuminated under 250 nm (UVC) and obtained faster dynamic behavior for tr / tf = 12.33 s / 0.33 s. In contrast, the devices annealing in N2 obtained higher Idark and Iphoto than without annealing which results in higher Responsivity reaching 63.96 A/W @5V illuminated under 250 nm (UVC) while the slightly worse dynamic behavior for tr / tf = 23.82 s / 0.88 s. The Idark for device above are ~1.0E-13 and ~1.0E-10. Whether the device annealing in O2 or N2, both performed good selectivity to UVC band estimated by RUVC/UVA reaching 7 × 10^4及6 × 10^2.
Based on the MSM device mentioned above, we fabricated P-NiO/N-ZnGa2O4 Photodiode, deposited P-NiO thin film by RF-sputtering. The built-in electric field in P-N junction is successfully obtained to further lower the Idark at level for 1.0E-13 and 1.0E-12 for two devices. Moreover, the improvement of the dynamic behavior for two devices is also reached by value of tr / tf = 2.10 s / 0.36 s ; 11.24 s/ 0.73 s.
In order to know the thickness, chemical composition, crystallinity, crystal directions, oxygen vacancies, refractive index, extinction coefficient and material energy bandgap of zinc gallium oxide film, the (1) Scanning Electron Microscope, (2) Transmission Electron Microscope, (3) X-ray Diffraction, (4) Energy-dispersive X-ray Spectroscopy, (5) X-ray Photoelectron Spectroscopy and (6) Ellipsometry are adopted in this research.
The thickness of active layers for the devices is confirmed through the Transmission and Scanning Electron Microscope. Also, the existence of crystallinity in films after annealing is shown by X-ray Diffraction. Following, chemical analysis for cross-section is given by the Energy-Dispersive X-ray Spectroscopy which is very close to the stoichiometric of ZnGa2O4. For the proportion of oxygen vacancies in the films, we obtained the analysis with X-ray photoelectron Spectroscopy and analyze the difference between device with and without annealing, which is confirmed that the conductivity is effect by it. Final, it is confirmed the wide bandgap (5 eV) for ZnGa2O4 which is suitable for UVC band detection by the attenuation factor and refractive index obtained by Ellipsometry.
In this thesis, the zinc gallium oxide ultraviolet photodetectors fabricated by the ultrasonic spray pyrolysis deposition have the advantages of the low cost and rapid process relative to other deposition methods. The annealing process could be simply introduced in obtain the crystallinity in films. We believe that the ultrasonic spray pyrolysis deposition has great potential and advantages in the industrial applications.

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