| Summary: | 碩士 === 國立臺灣海洋大學 === 光電科學研究所 === 96 === Persistent photoluminescence (PL), PL, Cathodoluminescence (CL), Hall and scanning Kelvin probe microscopy (SKPM) measurements were performed to investigate the effects of sulphur treatment on the optical and electrical properties of n-GaN film by using 20% (NH4)2S solution. It was found that all the enhancement in the intensity of near band-edge PL, the enhancement in free electron density, the observation of persistent PL phenomenon, and the increase in surface contact potential or the reduction in the Schottky barrier height can be understood consistently by considering the removal of the surface gallium oxides and the effective passivation of surface defects of GaN films. It was also noted by the results of SKPM measurements that the surface treatment by (NH4)2S solution could improve the surface property of GaN by possibly reducing the defect-related surface states. And thus, this could lead to the reduction in the surface band bending and the lowering of Schottky barrier height which is as high as 0.306 eV. In additions, the CL measurements with varied electron energy showed the depth to result in the best enhancement in luminescent intensity is about 94 nm.
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