以矽基板成長氮化鎵可降低氮化鎵光電元件的成本，但由於兩種材料的晶格常數與熱膨脹係數不匹配，需以適當的緩衝層來減輕磊晶層中的應力，本研究以單斜結構β氧化鎵作為氮化鎵在矽基板上的緩衝層，希望能開發出新的磊晶技術。 單斜結構β氧化鎵具有高穩定性等性質，並與氮化鎵僅有2.6%的晶格失配率，我們使用濺鍍系統，於矽<111>基板上沉積氧化鋅/氧化鎵緩衝層，再利用高溫氨氣環境退火，使氧化鎵與氨氣進行反應，進而生成氮化鎵薄膜。 藉由比較不同氧化鋅厚度，我們發現在未使用氧化鋅薄膜之試片並無法使氧化鎵與氨氣產生反應，這是由於氧化鋅可改變薄膜表面能量分布，導致缺陷產生，而缺陷的分子斷鍵會捕捉游離的氣態氮與鎵分子。另外我們調變退火時的時間與氨氣流量，發現較低的10sccm氨氣流量可以導致較高品質的氮化鎵，且過短的氨化時間並不足以使氮化鎵形成薄膜。 另外我們使用了MOCVD系統磊晶氮化鎵，並於磊晶前進行10分鐘通入氨氣的流程，加入此流程可使氮化鎵磊晶品質提高，另外在此製程下，使用氧化鋅插入層依然有效提高品質。 ;The growth of GaN on Si can reduce manufacturing cost of nitride-based optoelectronic devices. However, due to the significant mismatch in lattice constant and thermal expansion coefficient mismatch between GaN and Si, we need to use buffer layer to mitigate the strain in GaN epi-layers. This study investigates the possibility of employing monocline β-Ga2O3 as the buffer layer for the growth of GaN on Si. The lattice mismatch between β-Ga2O3 and GaN is only 2.6%. In this project, we deposited ZnO/ β-Ga2O3 on Si <111> substrate, and nitridized the oxide layer in high-temperature NH3 ambience in order to attain a thin GaN layer for subsequent epitaxial growth. It is found that inserting a ZnO layer between β-Ga2O3 and Si can improve the crystal quality of GaN. The result is attributed to the fact that ZnO thin film can change the surface energy of β-Ga2O3 to facilitate the bonding between Ga and N. The effect of ZnO thickness, annealing time, and NH3 flow rate on GaN epitaxy is analyzed. We also grow GaN on ZnO/β-Ga2O3/Si with metal organic chemical vapor deposition. The GaN epi-layer is found be polycrystalline. Methods to enhance the epitaxial qualities are proposed.
