研究目的
Investigating the morphology of InGaN layers grown on GaN substrates as a function of growth conditions and miscut angle, and comparing it to growth on GaN/sapphire templates to understand the effects of supersaturation on morphology and internal quantum efficiency.
研究成果
The research demonstrates that InGaN morphology transitions from steps to 2D islands to 3D dots with increasing supersaturation, influenced by growth temperature, rate, and miscut angle. Stepped morphology yields the highest IQE, and GaN substrates facilitate this morphology more easily than GaN/sapphire templates due to lower supersaturation and dislocation density. This insight can guide optimization of InGaN growth for high-efficiency optoelectronic devices.
研究不足
The study is limited to specific growth conditions and substrate types; it does not explore a full range of supersaturation values or other material systems. The use of GaN substrates with low dislocation density may not be representative of all industrial applications, and the calculations of supersaturation involve assumptions that could introduce errors.
1：Experimental Design and Method Selection:
The study used metalorganic vapor phase epitaxy (MOVPE) to grow InGaN layers on c-plane GaN substrates, with variations in growth temperature, growth rate, and miscut angle to investigate morphological changes. Atomic force microscopy (AFM) was employed to analyze surface morphology, and X-ray diffraction (XRD) for thickness and InN mole fraction measurements. Photoluminescence (PL) was used to assess internal quantum efficiency (IQE).
2：Sample Selection and Data Sources:
InGaN layers with 4–6 nm thickness were grown on GaN substrates with different miscut angles (0.24°, 0.51°, 0.97°) and on GaN/sapphire templates. Samples were categorized into three series based on growth temperature, growth rate, and miscut angle variations, as detailed in Table
3：24°, 51°, 97°) and on GaN/sapphire templates. Samples were categorized into three series based on growth temperature, growth rate, and miscut angle variations, as detailed in Table List of Experimental Equipment and Materials:
1.
3. List of Experimental Equipment and Materials: A horizontal MOVPE reactor was used with triethylgallium (TEG), trimethylindium (TMI), ammonia (NH3), and nitrogen as sources. Equipment included AFM for morphology, XRD for structural analysis, and a He-Cd laser for PL measurements.
4：Experimental Procedures and Operational Workflow:
InGaN layers were grown under controlled conditions of temperature, pressure (500 hPa), and gas flows. AFM images were taken in non-contact tapping mode, XRD ω-2θ scans were performed, and PL was measured at room temperature and 77 K to calculate IQE.
5：Data Analysis Methods:
XRD data were compared with kinematic diffraction simulations to determine thickness and InN mole fraction. AFM images were analyzed for step height, island size, and roughness. PL data were used to compute IQE as the ratio of intensities at R.T. and 77 K.
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