氮化鎵元件的漏電流是跟磊晶成長和元件製程相關的重要議題，因為漏電流會導致元件電特性變差。在本篇論文中漏電流依據導通的路徑被區分為水平式與垂直式漏電流，而造成漏電流的原因和解決漏電流的方式將會在本篇論文中討論。
在電漿輔助分子束磊晶系統中，利用氮氣電漿清潔氮化鎵模板表面可以有效的減少殘留於再成長介面的氧和碳原子濃度，同時也能夠保持介面的平整性與品質，氧原子濃度由1.49×1019減少至8.92×1017 cm-3，碳原子濃度由7.22×1018減少至3.38×1016 cm-3。本論文利用氮化鋁鎵/氮化鎵高電子遷移率電晶體結構來探討水平式漏電流議題，經過在900°C氮氣電漿處理15分鐘後，氮化鋁鎵/氮化鎵高電子遷移率電晶體的電子遷移率由469提升至730 cm2/V-s，氮化鋁鎵/氮化鎵蕭基能障二極體的水平式漏電流由1.54減少至0.038 A/cm2。
分別在成長溫度750、785、815和845°C成長無參雜氮化鎵，以此方式來增加鎵原子在表面的揮發速率，增加鎵原子的揮發速率能抑制被鎵包覆的線差排的產生。本論文利用準垂直式氮化鎵蕭基能障二極體來探討垂直式漏電流的議題。在高溫成長的氮化鎵中，線差排會以凹洞的形式終結在氮化鎵表面，當成長溫度從815升高到845°C，凹洞的平均直徑從507增加至379 nm，這是由於表面上的鎵與氮原子在高溫下能夠獲得更多的動能以利本身移動。由於背景參雜濃度隨著成長溫度升高而降低，故準垂直式蕭基能障二極體的串聯電阻也隨成長溫度升高而增加。藉由在高溫情況下成長氮化鎵，蕭基能障二極體的反向漏電流由6.5×10-2減少至1.8×10-5 A/cm2，大幅降低的漏電流歸因於於氮化鎵中被鎵包覆的線差排的產生能夠被抑制。

Leakage currents, which could degrade electrical properties of GaN devices, are an important issue related to epitaxial layer growth and device processing. In this thesis, according to the conduction path directions, the origins and solutions of lateral and vertical leakage currents in GaN multiple layer structures are investigated.
By exposing the GaN template surface to N2 plasma in the plasma-assisted molecular beam epitaxy (PAMBE) system, the concentration of residual oxygen and carbon at the growth interface are effectively reduced from 1.49×1019 to 8.92×1017 and from 7.22×1018 to 3.38×1016 cm-3, respectively, while preserving a good interface quality. The AlGaN/GaN high electron mobility transistor (HEMT) structure is used to study the lateral leakage current problem. The mobility of the AlGaN/GaN HEMT is increased from 469 to 730 cm2/Vs, and the lateral leakage current of AlGaN/GaN Schottky barrier diodes (SBDs) decreased from 1.54 to 0.038 A/cm2, after N2 plasma treatment at 900°C for 15 min.
Undoped GaN was grown at 750, 785, 815 and 845°C to increase the Ga evaporation rate on the surface such that the formation of Ga-decorated threading dislocations (TDs) is suppressed. Quasi-vertical GaN SBDs are utilized to investigate the vertical leakage current issue. It was found that TDs terminated as pits on the GaN surface grown at high temperatures. The average diameter of pits decreased from 507 to 379 nm as GaN growth temperature increased from 815 to 845 °C as Ga and N adatoms gain more kinetic energy to migrate on the surface. The series resistance of quasi-vertical SBDs becomes larger with increasing the growth temperature, which is attributed to the lower background doping concentration achieved in GaN. The reverse leakage current of quasi-vertical SBDs grown at high temperature is reduced from 6.5×10-2 to 1.8×10-5 A/cm2. The significant reduction of the leakage current is attributed to the suppression of Ga-decorated TDs formation in GaN films.

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