| 摘要: | 氮化鎵具有能帶寬和熱穩定性的優勢，因此在半導體材料中具有舉足輕重的地位，另外由於其非線性係數較大，所以也利於非線性領域的研究。傳統上在沉積氮化鎵薄膜時，幾乎都是採用有機金屬化學氣相沉積法(metal organic chemical vapor phase deposition, MOCVD)，或者是利用晶圓接合(wafer bonding)的方式，前者的優勢在於其能沉積出高品質且具晶格結構的氮化鎵薄膜，但其缺點是沉積時須考慮到晶格的匹配度，若晶格匹配度不佳則無法沉積出高品質的薄膜，此種沉積方式通常沉積於藍寶石基板上，但藍寶石基板價格較為昂貴，和互補式金屬氧化半導體(complementary metal oxide semiconductor, CMOS)製程相容性不佳，且其製程需要在高溫中進行；而晶圓接合雖然可以接合在與CMOS製程相容的基板上，但同樣需要先沉積於晶格匹配的基板，且須經過較為繁複的製程步驟，最後導致薄膜表面品質較不理想。為了能於不同的基板上沉積出高品質的薄膜，因此本論文中使用了高功率磁控脈衝濺鍍法(high-power impulse magnetron sputtering, HiPIMS)來沉積氮化鎵薄膜，此種沉積方式是以高能量離子轟擊表面進行薄膜濺鍍，因此其優勢在於能在室溫沉積且不須晶格匹配，使其能輕易沉積於不同的的基板上。
論文中首先會介紹波導和微環形共振腔的基礎理論，並根據設計的光罩模擬其模態和場型，分析其是否能順利且穩定的傳輸於波導結構中；接著藉由模擬來比較有無表面披覆層對於場型傳輸的影響；最後則是藉由模擬來確認混合式波導的可行性，並且比較不同材料混合式波導的彎曲損耗，以說明氮化鎵混合式波導的優勢。接著本論文利用能沉積於不同基板的優勢，嘗試使用矽、玻璃和石英這三種基板沉積氮化鎵薄膜，來製作波導及微環形共振腔，接著藉由改善各種製程和光罩設計，來優化低限制波導和高限制波導的損耗，以及嘗試提升微環形共振腔的品質因子。最後成功的於石英和玻璃基板上，製作出可量測到共振的氮化鎵微環形共振腔，並且利用氮化鎵混合式波導做出品質因子達104的微環形共振腔。
本論文使用HiPIMS將氮化鎵沉積於石英和玻璃基板上，製作出具共振的微環形共振腔，並且首次嘗試用氮化鎵製作出混合式波導，避免掉蝕刻所帶來的損耗，為氮化鎵波導提供了更多元的發展方向。
;Gallium nitride (GaN) has advantages in wide bandgap and thermal stability, making it a crucial material in the semiconductor industry. Additionally, due to its large nonlinear coefficient, it is also beneficial for research in the field of nonlinear optics. Traditionally, GaN thin films are predominantly deposited using metal-organic chemical vapor deposition (MOCVD) or wafer bonding techniques. The advantage of MOCVD lies in its ability to deposit high-quality GaN thin films with lattice structures. However, its drawback is the need to consider lattice matching during deposition. Without good lattice matching, high-quality thin films cannot be achieved. Typically, GaN thin films are deposited on sapphire substrates, which are expensive, lack compatibility with complementary metal-oxide-semiconductor (CMOS) processes, and require high-temperature processing. On the other hand, wafer bonding allows integration onto CMOS-compatible substrates, but the initial deposition still requires lattice-matched substrates, involves more complex processing steps, and results in poorer surface quality of the thin films. To enable the deposition of high-quality thin films on a variety of substrates, this thesis employs high-power impulse magnetron sputtering (HiPIMS) for GaN thin film deposition. This deposition method utilizes high-energy ion bombardment to sputter the thin film onto the surface. Its advantages include the ability to deposit at room temperature without requiring lattice matching, allowing easy deposition on various substrates.
The thesis begins with an introduction to the fundamental theories of waveguides and micro-ring resonators, followed by simulations of the designed photomask to analyze the modes and field distributions, ensuring stable and efficient propagation within the waveguide structure. Simulations are then conducted to compare the effects of surface coating layers on field propagation. Finally, the feasibility of hybrid waveguides is verified through simulations, and the bending losses of hybrid waveguides made from different materials are compared, demonstrating the advantages of GaN hybrid waveguides. Leveraging the ability to deposit GaN films on various substrates, this thesis fabricates waveguides and micro-ring resonators using GaN thin films deposited on silicon, glass, and quartz substrates. By improving fabrication processes and optimizing photomask designs, efforts were made to reduce losses in both low-confinement and high-confinement waveguides while enhancing the quality factor of microring resonators. Ultimately, micro-ring resonators with resonances were successfully fabricated on quartz and glass substrates, and hybrid waveguides made with GaN achieved a micro-ring resonator quality factor of 104.
In conclusion, this thesis demonstrates the use of HiPIMS to deposit GaN on quartz and glass substrates to fabricate micro-ring resonators with resonances. Additionally, hybrid GaN waveguides were first developed to avoid losses associated with etching, providing a more versatile approach for GaN waveguide applications. |
