在本論文中，將利用化學分析電子光譜儀研究氯氣處理對氮化鎵試片表面的影響。此研究過程為將氮化鎵試片置於陽極鉑電極下方並放入鹽酸電解液中，電解時陽極鉑電極會產生氯氣並和有機金屬氣相磊晶機台成長出來的氮化鎵表面之鎵原子懸鍵反應生成氯化鎵，此產物容易溶解於化學溶液中進而在氮化鎵表面形成鎵原子位置的空缺。此外，電解所生成的氯氣溶於水後形成次氯酸，而次氯酸會氧化氮化鎵表面而形成氧化鎵，因此氯氣處理所生成的氯化鎵和氧化鎵產物將分別會在氮化鎵表面形成鎵原子位置的空缺及減少氮原子位置的空缺。利用氯氣處理法將可提高氮化鎵表面電洞濃度並且獲得較佳的鎳金/p型氮化鎵歐姆接觸特性，其特徵電阻值為4.8×10-6 Ω-cm2。利用此方法應用於氮化鎵發光二極體不僅可改善其元件光電特性，包括操作電壓在20 mA時從3.3伏特降至3伏特、光輸出功率在300 mA時可增加約1.25倍，並可以減少氮化鎵的表面態密度進而降低漏電流的產生。將氯氣處理應用於n型氮化鎵可獲得較高蕭特基位障和較佳之理想因子，這是由於氯氣處理可以有效減少鎵原子之懸鍵並形成氧化鎵鈍化表面態，所以經氯氣處理過後之氮化鎵試片具有較強的光激發光譜及較長的載子生命週期。而此外，將氯氣處理應用於蕭特基型光檢測器可以獲得較低之漏電流及較理想的量子效應和內部增益的乘積，在操作波長330 nm、操作電壓-10伏特時其量子效應和內部增益的乘積在未氯氣處理和氯氣處理分別為650%和100%。

The surface of a chlorine-treated GaN semiconductor was analyzed using X-ray photoelectron spectroscopy to investigate the function and mechanism of oxidation. The grown sample was placed in an electrolytic solution (HCl(aq)) underneath a Pt anodic electrode. The produced chlorine adhered and reacted with the GaN sample. The Ga dangling bonds of the Ga-face GaN surface grown using the MOCVD system reacted with chlorine to form GaClx. The GaClx can be easily dissolved in the chemical solvent to induce Ga vacancies on the surface of the GaN sample. The chlorine dissolves in the water to form HClO, which in turn oxidizes GaN and enhances the formation of GaOx on the GaN surface. The chlorine-treated GaN sample induces more Ga vacancies and decreases the N vacancies due to the formation of GaClx and GaOx, respectively. Therefore, a relatively higher Ohmic performance with a specific contact resistance of 4.8×10-6 Ω-cm2 can be obtained for Ni/Au metal contact patterned on the chlorine-treated p-type GaN via the enhanced hole concentration.
The electrical and optical performance of multiple-quantum-well (MQW) InGaN/GaN light-emitting diodes was improved by using chlorine to treat the surface of the p-type GaN layer. Compared to the untreated sample, the current-voltage (I-V) characteristics show that the forward voltage of the chlorine-treated MQW InGaN/GaN LEDs is decreased from 3.3 V to 3.0 V at 20 mA and the light output power is increased 1.25 times at 300 mA. The reverse leakage current of the chlorine-treated MQW InGaN/GaN LEDs was also significantly decreased due to the passivation of surface states by chlorination treatment of the p-type GaN layer. The Schottky barrier height and ideality factor of the chlorine-treated GaN Schottky diodes were improved.
The photoluminescence (PL) intensity and carrier lifetime of the chlorine-treated n-type GaN increased by using PL and time-resolved PL measurements. The improved performance of the chlorine-treated GaN Schottky diodes can be attributed to the reduction of surface states. The decrease of surface states resulted from the reduction of Ga dangling bonds and the occupation of N vacancies due to the passivation function of the GaOx formation on the surface of n-type GaN using chlorination treatment. The products of quantum efficiency and internal gain of the GaN Schottky UV-photodetector without and with chlorination treatment under a reverse voltage of -10 V at a wavelength of 330 nm are 650% and 100%, respectively.

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