Yu-Chiao Lin

Growth of InGaN/GaN quantum wells with graded InGaN buffer for green-to-yellow light emitters

We have studied the growth of high-indium-content In x Ga1− x N/GaN double quantum wells (QWs) for yellow and green light emitters by plasma-assisted molecular beam epitaxy at a low substrate temperature (570 °C). By introducing a graded In y Ga1− y N buffer layer, the PL intensity of QWs can be increased sixfold compared with that of the original structure. In addition, the indium content in InGaN QWs was increased owing the prolonged growth time of the graded In y Ga1− y N buffer layer. After adjusting to optimal growth conditions, we achieved In x Ga1− x N/GaN QWs with x = 0.32. Photoluminescence measurements showed that the emission wavelength from In x Ga1− x N/GaN QWs was 560 nm (2.20 eV). The optimal condition for the gradient In y Ga1− y N buffer layer was obtained for light emission from green to yellow.

Growth and Characterization of M-Plane GaN Thin Films Grown on γ-LiAlO2 (100) Substrates

M-plane GaN thin films were grown on LiAlO2 substrates under different N/Ga flux ratios by plasma-assisted molecular beam epitaxy. An anisotropic growth of M-plane GaN was demonstrated against the N/Ga flux ratio. As the N/Ga flux ratio decreased by increasing Ga flux, the GaN surface trended to a flat morphology with stripes along [112-0]. According to high-resolution X-ray diffraction analysis, Li5GaO4 was observed on the interface between GaN and LiAlO2 substrate. The formation of Li5GaO4 would influence the surface morphology and crystal quality.