賴昆佑

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.