在本論文中，我們利用有機金屬氣相磊晶法成長三五族氮化物半導體材料並製作相關之光電元件。首先，我們使用偏離c軸方向1度的藍寶石基板生長氮化鎵可獲得磊晶品質較佳、缺陷較少之磊晶薄膜，其蝕刻陷斑密度為1.2×107 cm-2；從變溫霍爾量測實驗發現，在1度傾斜角度藍寶石基板上的氮化鎵磊晶層只存在一個活化能值，並無其他缺陷相關之活化能數值。
就氮化銦磊晶而言，所有試片表面均為網狀結構，並且當隨著成長溫度增加時，表面變得更加粗糙，而生長速率亦隨之增加，在675 oC生長之氮化銦磊晶薄膜，其生長速率可達到470 nm/hr；而在625 oC生長的氮化銦磊晶層可達到最高的電子遷移率為1300 cm2/Vs，以及最低的載子濃度為4.6 × 1018 cm-3。另一方面，在高成長壓力生長的氮化銦試片，其表面型態呈現出密集扭曲的晶粒型態，同時在低壓成長的試片在介面處有空隙存在。在500 mbar生長的氮化銦磊晶層可達到最高的電子遷移率為1415 cm2/Vs，以及載子濃度為4.2 × 1018 cm-3。另外，對於在高五三比條件下生長的氮化銦試片，其表面型態較為平坦，同時可提高側向生長速率。在五三比為15200生長的氮化銦磊晶層可達到最高的電子遷移率為1333 cm2/Vs，其載子濃度為5.9 × 1018 cm-3。
就氮化鎵發光二極體方面，在1度偏角度藍寶石基板上製作的氮化銦鎵磊晶薄層有較均勻的銦原子分佈，並且在偏角度基板上製作的發光二極體有較小的暗電流。因此，利用偏角度藍寶石基板生長的發光二極體有較強的發光強度，並且隨著注入電流增加，發光波長幾乎不會改變。
在氮化鎵紫外光偵檢器方面，首先在氮化鎵p-i-n結構偵檢器的吸收層中間插入一層低溫氮化鎵插入層，由於載子累增效果的影響，此偵檢器可在一個小電場(~0.4 MV/cm)的情況下增加響應度；同時也觀察到13倍的光電流增益以及較大的離子化係數(α=3.1×105 cm-1)；因此，具有低溫氮化鎵插入層的偵檢器可達到2.27 A/W高峰值響應度。另一方面，具有低溫氮化鋁插入層的偵檢器即使在40 V高逆偏壓仍有非常小的暗電流(2~3 × 10-11 A)。雖然，在氮化鋁/氮化鎵介面的高位能障在低逆偏壓時會稍微降低偵檢器的響應度，但因為暗電流非常小的關係，即使在高逆偏壓下，仍有很高的紫外光對可見光的拒斥比。另外，利用二氧化鈦奈米粒子粗化表面的氮化鎵p-i-n偵檢器，其響應度與外部量子效率可提升60%；並且可增強不同入射角度的光吸收量；因此，具有粗化表面的偵檢器可達到9.2×1013 cmHz1/2W-1的高偵測度。
在氮化鎵光伏元件方面，隨著氮化銦鎵磊晶層銦含量的增加，磊晶品質亦隨之降低。以我們的磊晶系統，可以達到銦含量60 %的氮化銦鎵磊晶生長。然而，對氮化物太陽電池磊晶而言，氮化銦鎵分解與相分離的現象為主要問題。因此，我們製作氮化物光伏元件時以低銦成份的氮化銦鎵磊晶層作為吸收層，此光伏元件的輸出功率密度與填充因子分別為0.3 mW/cm2和70%。

In this dissertation, we prepared III-V nitride semiconductor materials and related optoelectronic devices by using metalorganic vapor phase epitaxy. First, the better crystalline quality and less dislocations of GaN epitaxial layers can be achieved by using 1o off-axis c-plane sapphire substrates. It was found that the etching pits density of GaN films on vicinal substrates is as low as 1.2×107 cm-2. From temperature-dependent Hall measurement, it was found that only one activation energy can be found from the GaN epitaxial layers grown on 1° tilted sapphire substrate, and no other defect-related activation energy can be found.
For InN epitaxy, it was found that surfaces of these samples were all reticular and the sample surface became rougher as we increased the growth temperature. It was also found that growth rate increased with increasing growth temperature and the growth rate could reach 470 nm/hr for the InN epitaxial layer grown at 675oC. Furthermore, it was found that we achieved the highest mobility of 1300 cm2/Vs and the lowest carrier concentration of 4.6 × 1018 cm-3 from the InN epitaxial layer grown at 625oC. On the other hand, it was found that surface morphologies were densely twisted grains for InN samples grown at high pressures while voids exist in the samples grown at low pressures. It was also found that we achieved a mobility of 1415 cm2/Vs and a carrier concentration of 4.2 × 1018 cm-3 from the InN epitaxial layer grown at 500 mbar. In addition, it was found that the surface morphologies of InN samples become smooth at high V/III ratio condition. It was also found that the lateral growth can be enhanced during the InN epitaxy under high V/III ratio. Furthermore, it was found that the mobility of 1333 cm2/Vs with corresponding the concentration of 5.9 × 1018 cm-3 can be achieved from the InN sample grown at the V/III ratio of 15200.
For GaN-based LEDs, it was found that indium atoms distributed much more uniformly in the thin InGaN epitaxial layers prepared on 1o off-axis sapphire substrates. It was also found that the dark current of LED grown on vicinal cut sapphire substrate is smaller. Furthermore, it was found that we could achieve stronger EL intensity with emission wavelength much less sensitive to injection current from the LEDs with vicinal cut sapphire substrate.
For GaN ultraviolet (UV) photodiodes, we first prepared GaN p-i-n structures with a low-temperature (LT) GaN interlayer inserted in the middle of absorption layer. It was found that the responsivity of the photodiode with LT-GaN interlayer can be enhanced at a small electric field (~0.4 MV/cm) due to the carrier multiplication effect. The UV photocurrent gain of 13 and large ionization coefficient (α=3.1×105 cm-1) were also observed in the detector with LT-GaN interlayer. Furthermore, we can achieve a large peak responsivity of 2.27 A/W from the photodiode with LT-GaN interlayer. On the other hand, the photodiodes with a LT-AlN interlayer reveal a significantly low dark current at a range of 2~3 × 10-11 A even under a very high reverse bias of 40 V. Although the high potential barrier at AlN/GaN interface would slightly reduce the responsivity of photodetector under low reverse biases, the high UV-to-visible rejection ratio of the photodetector with LT-AlN interlayer could be achieved under high reverse biases due to its very low dark current. Besides, the GaN p-i-n photodiodes with a TiO2 nano-particles roughened surface show a 60% improvement of responsivity and external quantum efficiency. It was also found that light absorption can be enhanced from various incident angles by the TiO2 roughened surface. Furthermore, the high detectivity of 9.2×1013 cmHz1/2W-1 can be achieved from the photodiode with a rough surface.
For GaN-based photovoltaic devices, it was found that crystalline quality of InGaN epitaxial layers reduced with increasing In composition. The In composition of 60% in InGaN epitaxial layers can be achieved by our epitaxial system. However, dissociation and phase separation of InGaN are the main issues for nitride-based solar cell epitaxy. Thus the InGaN epitaxial layers with low In composition were used as absorption layer for fabricating nitride-based photovoltaic devices. It was found that the output power density and fill factor of such photovoltaic devices are around 0.3 mW/cm2 and 70%, respectively.

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