| Summary: | 碩士 === 國立臺灣海洋大學 === 光電科學研究所 === 94 === We have performed the polarization modulation near-field scanning optical microscopy (PM-NSOM) measurements to investigate the correlation between crystalline and optical properties of InGaN epilayers and crystalline quality of In-rich InGaN epilayers.
The PM-NSOM results show the nanoscale domain-like structures which exhibit good correspondence to the morphological images by SEM measurement. It is found the In-rich regions formed at the periphery of the hexagonal pits. These In-rich regions show good crystallinity and high recombination efficiency. We point out that the combination of PM-NSOM and NSOM-PL is a powerful tool for investigating the correspondence between the local morphology and the optical properties of the nanostructures.
The crystalline properties of In-rich InGaN films with Ga concentration varying from 0% to over 30% were investigated by PM-NSOM measurements. PM-NSOM measurements showed that the crystallinity of InGaN films were strongly dependence on the Ga concentration. The average crystallinity of InGaN film was found to decrease with the increase in Ga concentration of InGaN films. On the other hand, the RMS crystallinity exhibited a different dependence on the Ga concentration for the In-Rich InGaN films. The RMS crystallinity of InGaN films first decreased with the increasing Ga concentration, reached a minimum for the InGaN film with 8% Ga concentration, and then increased again with increasing Ga concentration. Surprisingly, the RMS crystallinity of InGaN films shows the same trend in the dependence of PL intensity on the Ga concentration in InGaN films. It was concluded that for the InGaN films with different Ga content grown at the same temperature, the RMS crystallinity of the epifilms accounts for PL emission efficiency of the epilayers.
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