Nucleation layer temperature effect on AlN epitaxial layers grown by metalorganic vapour phase epitaxy

AlN samples have been grown on sapphire substrate using nucleation layers (NLs) having different growth temperatures. The growth temperature of the NL has been varied over a wide range of temperatures highlight the effects on the quality of the AlN epilayer. The AlN samples have been characterized by high-resolution X-ray diffraction (HRXRD), atomic force microscope (AFM), Raman scattering spectrometer, and spectrophotometer. The obtained results demonstrate the temperature of NL has a direct effect on the quality of the AlN sample and occurs major differences in the quality of structure, surface morphology, and amount of strain in the AlN epilayers. Based on HRXRD measurement results, when the growth temperature of AlN NL is raised to 1075 degrees C, the crystal quality has improved owing to both the density of AlN nucleation islands reduction and the grain size outgrow. However, continuing to increase the growth temperature of the AlN NL layer begins to degrade the quality. In addition, the findings obtained from the Raman measurement demonstrates that the tensile stress can be control through NL growth temperature. Therefore, as can be seen from the characterization results, the growth temperature of AlN NL is important to obtain an AlN sample with high quality.