| Summary: | 碩士 === 國立中山大學 === 物理學系研究所 === 100 === In this thesis, we have studied the growth of M-plane GaN thin film on LiGaO2 (100) substrate by Plasma-Assisted Molecular Beam Epitaxy. We found that the growth of GaN thin films on as-received LiGaO2 substrates is poly-crystalline by analysis of X-ray diffraction, and these of GaN thin films were peeled off after thin film process. Using atomic force microscopy (AFM) to scan the surface of as-received LiGaO2 substrate, we found that many particles which are Ga2O3 existed on the surface of as-received LiGaO2.
The annealing ambient for LiGaO2 substrates in vacuum and air ambient has been studied in order to improve the surface of LiGaO2. The scanning results of AFM shows that the crystal quality and stress of M-plane GaN grown on LiGaO2 (100) substrate pre-annealed in air ambient is significantly improved. We conclude that the reason of GaN peeling off from LiGaO2 substrate is attributed to stress between GaN/ LiGaO2.
The measurement of polarization-dependent PL shows that the luminescence intensity of growing sample increases and reaches a maximum at φ = 90° (E⊥c), which indicates the growing samples is M-plane GaN as well. The microstructure of growing samples was characterized by transmission electron microscopy. We found that the formation of stacking fault in GaN is attributed to the growth of GaN on cubic-Ga2O3 nano-particles. The formation of Ga2O3 nano-particles can be suppressed by pre-annealing LiGaO2 substrate in air.
It revealed that the thermal annealing LiGaO2 substrate in air ambient can improve the surface of LiGaO2 substrate effectively, and then one can grow a high quality M-plane GaN thin film on the LiGaO2 substrate.
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