| Summary: | 碩士 === 逢甲大學 === 材料科學所 === 91 === The purpose of this study is to explore the effect of strained multi-layers on the behaviors of threading dislocations in GaN films. GaN films were grown on (0001) sapphire substrates by atomic layer epitaxy (ALE). Groups III metalorganics and NH3 were used as the sources of Al, Ga, and N elements. The precursors were carried into the reactor by purified H2. The surface morphology, crystallinity and optical properties of GaN films were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Photoluminescence(PL) measurement. Experimental results indicate that the crystalline and optical properties of HT-GaN films having intermediate AlN/GaN or Al0.5Ga0.5N/GaN strained multi-layer structures are better than those of the GaN film without multi-layer structure. TEM observations show that the insertion of HT-AlN/GaN(5nm/5nm) or Al0.5Ga0.5N/GaN(5nm/5nm) strained multi-layers was helpful to reduce TD density in GaN films considerably. The TD density reduction in a GaN film having an above-mentioned strained multi-layers structure is primarily due to TD annihilation and de- multiplication processes at the strained multi-layers structure.
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