非極性"a"面氮化銦鎵多重量子井成長在奈米圖樣基板之光學特性研究

Abstract

In this thesis, we investigated a-plane InGaN/GaN multiple quantum wells were grown on r-plane sapphire by metal organic chemical vapor deposition, and the difference of samples is nanorod depth of a-plane GaN templates. We utilized several methods including photoluminescence（PL）, atomic force microscopy（AFM）, and transmission electron microscopy（TEM）to investigate the optical characteristics and material structures of our samples. We have known that the crystal quality of a-plane GaN films was improved by using epitaxial lateral overgrowth on a nanorod GaN template by AFM and TEM. And from the temperature dependent PL measurement, we get the result which the value of IQEPL and activation energy is higher when the etching depth of nanorods is deeper. It means carries confinement in MQWs was enhanced by lowering defects of a-plane GaN templates. Moreover, the un-shift emission peak from the power-dependent PL measurement indicated the absence of QCSE within our samples. The polarization-dependent PL shows that the degree of polarization and peak energy shift decreased with increasing nanorods depth, which can be attributed to stain relaxed , injection carrier density and scattering. In the second part, we measure the internal quantum efficiency（IQE）of the MQWs, and the IQE of a-plane InGaN/GaN MQWs are approximately 39%(1.7um) more than 13%(as-grown). Next, using the measured data and knowing the B value, one can obtain nonradiative coefficient A. The measured nonradiative recombination coefficient A decreased one order as the etching depth increases from 0 to 1.7 um. It matched the variation of threading dislocation density and we could observe the best luminescence efficiency and quality with 1.7um nanorod sample.