本論文主要是在研究以有機金屬氣相磊晶法成長氮化鎵系列太陽能電池及光檢測器之研究，為了獲得最佳化p-GaN/i-InGaN/n-GaN結構的太陽能電池成長參數，因此InxGa1-xN吸收層的成長條件需要被適當的調整以及最佳化，如下所示:成長溫度為 815℃, TMGa流量為8 sccm,TMIn流量為250 sccm, NH3流量為12000 sccm, N2 (圓盤轉速)流量為200 sccm。為了有效地改善氮化鎵系列的太陽能電池品質，在本論文中具有漸進式InxGa1-xN吸收層的太陽能電池已經被設計和製作出。比較單層InxGa1-xN吸收層的太陽能電池，具有漸進式InxGa1-xN吸收層的太陽能電池的缺陷密度可以從5.6×108 cm-2降低至2.9×108 cm-2，其原因可以歸咎於晶格不匹配減少的關係。此外針對單層InxGa1-xN吸收層的太陽能電池相比，具有漸進式InxGa1-xN吸收層的太陽能電池擁有較小的漏電流而且漏電流可改善約77.3%。而且具有漸進式InxGa1-xN吸收層的太陽能電池的量子效率(~75%)也高於單層InxGa1-xN吸收層的太陽能電池(~40%)。在AM 1.5G太陽光光譜的量測下，具有漸進式InxGa1-xN吸收層的太陽能電池的開路電壓和短路電流密度分別為1.33 V和5.9×10-4 A/cm2，而填充因子和功率轉換效率分別為65%和0.51%，其效率是比單層InxGa1-xN吸收層的太陽能電池大(0.21%)。此外在本論文中，具有單層和多層抗反射層的太陽能電池也已經被製作出。針對不具有抗反射層的太陽能電池相比，具有單層和多層抗反射層的太陽能電池的表面反射率可以在波長330 nm和500 nm之間被降低至5%以下。針對不具有抗反射層的太陽能電池相比，具有多層抗反射層的太陽能電池的漏電流在逆向偏壓3 V時可以從16×10-6 A改善至0.8×10-6 A，而且在開路電壓和填充因子分別可改善100%和54.5%。與不具有抗反射層的太陽能電池相比，具有單層和多層抗反射層的太陽能電池的理想因子分別可改善19.4%和31.9%。在本論文的電極圖案設計中，具有各種指插狀電極的太陽能電池已經被製作出並且計算出每一個電極圖案的功率損失。在電極圖案設計中分別有3根、6根和12根類型的指插狀電極圖案，其名稱分別為SCs-Three, -Six and -Twelve，而不具有指插狀根數電極的太陽能電池命名為SCs-Zero。在電極圖案設計中，指插狀寬度的變化從10μm m變化至30 μm。由實驗中可以發現太陽能電池的電特性會因為指插狀電極的根數和寬度增加而變良好，短路電流密度會隨著指插狀電極的根數和寬度增加而增加，其中也發現開路電壓和填充因子並不會因為不同的電極圖案而有所變化。根據功率損失的計算，片電阻的功率損失在所有各項的功率損失中是最為嚴重的。其中也發現當指插狀電極的根數和寬度隨之增加時，片電阻的功率損失可以被有效地改善。與不具有指插狀電極的太陽能電池相比(448×10-9 w/cm2)，具有3根、6根和12根指插狀電極的太陽能電池且指插狀寬度為10μm m時，其各個電極中的片電阻功率損失分別可改善至242×10-9 w/cm2, 55.3×10-9 w/cm2, and 9.89×10-9 w/cm2。由此研究可得知，指插狀電極的最佳參數可以從功率損失的計算而獲得，且計算的結果和實際元件的量測有很好的一致性，而最佳指插狀電極的根數和寬度分別為12根和30m。在本論文中的最後為光檢測器的設計，具有金屬/氧化層/半導體結構(MIS)的Al0.35In0.01Ga0.64N UV-C 280 nm的光檢測器也已經被製作出。與波長操作在280 nm的Al0.4Ga0.6N/GaN異質結構的光檢測器相比，使用此Al0.35In0.01Ga0.64N/GaN的結構可以遭受較低的應力並且在光檢測器晶格鬆弛的情形可以從60%改善至4.48%。具有氧化層AlInGaN光檢測器的暗電流為2.78×10-8 A/cm2，其值比不具有氧化層的光檢測器小6個次方，其原因可歸咎於氧化層可增加表面能障的高度同時可減低在金屬與半導體之間的表面狀態密度。AlInGaN MIS光檢測器的最小雜訊等效功率和最大檢測率分別為9.37×10-12 w和1.85×1011 cmHz1/2w-1。為了有效地改善暗電流，多層接面Ni/Pd/Au金屬結構被應用在AlInGaN的光檢測器中。和傳統Ni/Au金屬結構相比，具有較高功函數的金屬(Pd)當做插入層形成多層接面Ni/Pd/Au金屬後可有效地降低暗電流，其值約可改善59.5%。在逆向偏壓5 V時，具有傳統Ni/Au金屬和具有多層接面Ni/Pd/Au金屬的光檢測器的光暗電流比分別為9.2和4.2×102。而在逆向偏壓3.5 V時，其響應率分別為1.8 mA/W和10.3 mA/W。就光響應率和排斥比而言，具有多層接面Ni/Pd/Au金屬的光檢測器的特性皆比傳統Ni/Au金屬的光檢測器良好。另一方面，多層接面Ni/Ir/Au金屬是被建議和製作在AlInGaN的光檢測器中。具有較高功函數的金屬(Ir)當做插入層形成多層接面Ni/Ir/Au金屬後可有效地降低光檢測器的暗電流，並且可增強元件的相關特性，其原因可歸咎於在多層接面金屬中金屬氧化物IrO2的金屬形成。在逆向偏壓3.5 V時，和具有傳統Ni/Au金屬的光檢測器相比，具有多層接面Ni/Ir/Au金屬的光檢測器的暗電流可從37×10-9 A/cm2 改善至 8.3×10-9 A/cm2，而在響應率的排斥比中也可從28.6改善至74。

The main purpose of the dissertation was investigation of GaN-based solar cells (SCs) and photodetectors (PDs) by using metalorganic vapor phase epitaxy (MOVPE). For obtaining optimal growth parameters of p-GaN/i-InxGa1-xN/n-GaN SCs, the growth conditions of the InxGa1-xN absorption layer needs to be adjusted and optimized as follows: growth temperature: 815℃, TMGa flow rate: 8 sccm, TMIn flow rate: 250 sccm, NH3 flow rate: 12000 sccm, and N2 flow rate (disk rotation): 200 sccm. In order to significantly improve quality of GaN-based SCs, the SCs with graded InxGa1-xN absorption layer (Device-GIAL) have been designed and fabricated. Compared with the SCs with a single InGaN absorption layer (Device-SIAL), threading dislocation density in the Device-GIAL could be reduced from 5.6×108 cm-2 to 2.9×108 cm-2, which was attributed to the reduction of lattice mismatch. Furthermore, the Device-GIAL had a smaller leakage current than that of the Device-SIAL. The leakage current of Device-GIAL was improved by 77.3%, as compared to Device-SIAL. The quantum efficiency of Device-GIAL (~75%) also was higher than that of Device-SIAL (~40%). Under AM 1.5G one-sun illumination, the open-circuit voltage and short-circuit current density of the Device-GIAL were 1.33 V and 5.9×10-4 A/cm2, respectively, while the fill factor and power conversion efficiency were 65% and 0.51%, respectively. The efficiency of the Device-GIAL was higher than that of the Devcie-SIAL (0.21%). Furthermore, the solar cells with a single-antireflection-layer (Device-SARL) and multiple-antireflection-layer (Device-MARL) have been fabricated. Compared with the SCs without an antireflection layer (Device-Control), the surface reflectance of the Device-SARL and Device-MARL can be reduced down to 5% at wavelengths between 330 nm and 500 nm. The leakage current of Device-MARL was improved from 16×10-6A to 0.8×10-6A under a reverse bias of 3V, as compared to Device-Control. The open-circuit voltage and fill factor of the Device-MARL were improved by 100% and 54.5%, respectively, as compared to Device-Control. The ideality factor could also be improved by 19.4% and 31.9% for devices with a SARL (SiO2) and MARL (Ta2O5/SiO2), respectively. In the electrode pattern design, solar cells with various interdigitated electrode patterns were fabricated and calculated the power loss for each electrode pattern. The electrode patterns were applied to the SCs and with 3, 6 and 12 fingers, denoted as SCs-Three, -Six and -Twelve, respectively. Solar cells without fingers, denoted as SCs-Zero were used as the control sample. The finger width (Wf) was varied from 10 to 30 μm. It was found that increasing number and width of fingers on SCs improved the electrical performance. The short-circuit current density increased with the increasing number and width of fingers, whereas the open-circuit voltage and fill factor did not significantly vary. According to power loss calculations, the sheet resistance loss (Psheet) was the largest resistance component in total power loss. A significant improvement in Psheet was observed when the number and width of fingers were increased. Compared with the SCs-Zero (448×10-9 w/cm2), the Psheet of SCs-Three, -Six, and -Twelve (Wf=10μm) can be improved to 242×10-9 w/cm2, 55.3×10-9 w/cm2, and 9.89×10-9 w/cm2, respectively. The optimum parameters of the interdigitated electrode pattern obtained from power loss calculations are in good agreement with those obtained from electrical analyses. The optimum parameters were 12 fingers with a width of 30m. Furthermore, aluminum indium gallium nitride (AlInGaN) UV-C 280 nm metal-insulator-semiconductor (MIS) photodetectors have been fabricated. Compared with the Al0.4Ga0.6/GaN heterostructure PDs operated at 280 nm, the use of Al0.35In0.01Ga0.64N/GaN structure should suffer less stress and the relaxation of Al0.35In0.01Ga0.64N/GaN PDs can be reduced from 60% to 4.48%. The dark current density of AlInGaN PDs with an insulating layer was 2.78×10-8 A/cm2, which were six orders of magnitude lower than that of PDs without an insulating layer, which can be attributed to the increasing surface barrier height and the decreasing density of the interface states between the metal and semiconductor. The AlInGaN MIS PDs also have the minimum noise equivalent power and the maximum detectivity of 9.37×10-12 w and 1.85×1011 cmHz1/2w-1, respectively. For decreasing the dark current, a Ni/Pd/Au contact was utilized on the AlInGaN PDs. With the inserting of the high work function metal (palladium, Pd), compared with the conventional Ni/Au contact, the multilayer Ni/Pd/Au contact can significantly reduce the dark current. The dark current of UV-C AlInGaN PDs with a multilayer Ni/Pd/Au contact can be relatively improved by 59.5 %. Under the 5 V reverse bias, the photo/dark current ratio of the PDs with a conventional Ni/Au contact and a multilayer Ni/Pd/Au contact were 9.2 and 4.2×102, respectively. The responsivity of Device-Ni/Pd/Au (10.3 mA/W@3.5V) was higher that that of Device-Ni/Au (1.8 mA/W@3.5V). The UV-C AlInGaN PDs with a multilayer Ni/Pd/Au contact have a better responsivity and rejection ratio than those of PDs with a conventional Ni/Au contact. On the other hand, a Ni/Ir/Au multilayer contact were proposed and fabricated on AlInGaN PDs. The inserting layer of the high work function metal (Ir) can significantly reduce the dark current of PDs and enhance the device performance, which can be attributed to the formation of IrO2 in multilayer contact. With a 3.5 V reverse bias, it was found that the dark current densities of PDs with a Ni/Ir/Au contact can be improved from 37×10-9 A/cm2 to 8.3×10-9 A/cm2, as compared to the PDs with a Ni/Au contact. The rejection ratio also can be improved form 28.6 to 74 when the PDs were with a Ni/Ir/Au contact.

Chapter 1
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Chapter 3
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Chapter 5
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