| Summary: | 碩士 === 國立交通大學 === 電子物理系所 === 93 === In this article, we analyzed the optical properties of the microstructures on AlGaN films with near-field scanning optical microscopy (NSOM). Different types of hillocks (mesa-like, tent-like, and pyramid-like) appeared on the film with AlN buffer layer while V-shape pit formed in the sample with GaN buffer layer.
In the NSOM spectra, the emission from the apexes of hillocks of different types of hillock is red-shifted in comparison with that from the plain surface. It may be due to the fluctuation of Al content [1], [2]. Since the spatial resolution of NSOM (∼100 nm) is capable of observing different regions inside single hillock. The luminescence from various probed regions on different types of hillock reflects their properties in detail. The spectra showed an extra peak （∼3.578eV）from the V-shape pit that differs from the near-band edge emission （∼3.693eV）. We suggested that this emission could be attributed to Ga vacancy [3]. From the intensity-mapping image, Ga vacancies seemed to be accumulated at the pit.
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