研究目的
To study the optical and structural properties of thick InGaN layers grown by MOCVD and MBE, and to determine the optical bandgap, Urbach energy, and FWHM of photoluminescence and Raman spectra depending on the InGaN alloy composition.
研究成果
The composition dependence of linewidths of photoluminescence and Raman spectra of thick InxGax-1N layers in the entire composition range was investigated. The experimental values of the PL FWHM are much greater than theoretical FWHM, suggesting that distribution of group-III atoms is not truly random and/or other broadening mechanisms take places.
研究不足
The experimental values of the PL FWHM are much greater than theoretical FWHM, suggesting that distribution of group-III atoms is not truly random and/or other broadening mechanisms take places. The outlier points on the graphs indicates that epitaxial growth of high-quality single-crystal InxGa1-xN layers in the composition range 0.4<x<0.6 is currently challenging.
1：Experimental Design and Method Selection:
The study involved the use of photoluminescence, optical transmission, and Raman spectroscopies, along with X-ray diffraction analysis to investigate the properties of InGaN layers.
2：Sample Selection and Data Sources:
Two sets of samples were grown on sapphire (0001) substrates with GaN buffer layer, one by MOCVD and the other by MBE.
3：List of Experimental Equipment and Materials:
Equipment included D8 Discover Bruker diffractometer, He-Cd (325 nm) and YAG:Nd (532 nm) lasers, halogen lamp, and Horiba Jobin-Yvon T64000 triple spectrometer.
4：Experimental Procedures and Operational Workflow:
X-ray diffraction analysis was performed to determine indium content. Photoluminescence studies were carried out at room and liquid nitrogen temperatures. Optical transmittance measurements and Raman spectra measurements were performed at room temperature.
5：Data Analysis Methods:
The optical bandgap was obtained by Tauc method. The Urbach energy was estimated from the spectral dependence of the absorption coefficient.
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