Characterization of Nanocrystallites of InGaN/GaN Multiquantum Wells by High-Resolution X-ray Diffraction

We report on the properties of nanocrystallites in InGaN/GaN multiquantum wells with different indium contents. The electroluminescence (EL) spectra are examined over a broad range of temperatures. According to the band-tail-filling model, greater inhomogeneity of nanocrystallites size is obtained from the temperature-dependent EL peak energy for the sample with higher indium content. To verify the results, the measured high-resolution X-ray diffraction curves are analyzed by the Warren-Averbach analysis model. Based on the model, it is found that the sample with higher indium content exhibits a wider nanocrystallite size distribution. In addition, X-ray diffraction line profile analysis shows stronger internal strain in the high-indium-content sample. Injection current-dependent EL measurements are also carried out. An evident blueshift in the EL peak energy is observed with increasing current in the sample with higher indium content, suggesting a stronger quantum-confined-Stark effect and internal strain. The experimental results coincide with the inference given by the X-ray diffraction line profile analysis.