| Summary: | 碩士 === 國立交通大學 === 光電工程學系 === 99 === In this study, we studied the optical properties of GaN/AlN nanostructures grown on c-plane sapphire substrate by metal-organic chemical vapor deposition (MOCVD).
By atomic force microscopy (AFM), nano-rod-like structures were observed on the surface. In raman spectra, a peak centered at about 605 cm-1 related to E2H mode of GaN QDs was observed, demonstrating the presence of the GaN quantum dots (QDs). Two peaks with wavelength of 310nm and 360nm were observed in PL spectra, which can be attributed to the nanostructures and QW emission respectively by theoretical calculations. Moreover, CL mapping also revealed the emission of 310 nm was from the nanostructures.
In PL measurement, it demonstrated that the screening effect of QCSE in the nanostructures was unobvious due to the large overlap of electron and hole wave functions resulted from small size nanostructures, and the carrier localization characteristic is observed.
TRPL measurement showed short radiative recombination time and higher room-temperature internal quantum efficiency in the nanostructures, and it indicated that nanostructures had stronger carrier confinement effect than QW.
Finally, the polarization characteristic demonstrated x- or y-polarization with DOP of 23.8% due to anisotropy of in-plane strain in the nanostructures.
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