Structural, morphological, and optical properties of AlGaN/GaN heterostructures with AlN buffer and interlayer

AlxGa1−xN/GaN x 0.3 heterostructures with and without a high-temperature HT AlN interlayer IL have been grown on sapphire Al2O3 substrates and AlN buffer/Al2O3 templates by metal organic chemical vapor deposition. The effects of an AlN buffer layer BL grown on an Al2O3 substrate and an AlN IL grown under the AlGaN ternary layer TL on structural, morphological, and optical properties of the heterostructures have been investigated by high-resolution x-ray diffraction, spectroscopic ellipsometry, atomic force microscopy, and photoluminescence measurements. The AlN BL improves the crystal quality of the AlGaN TL. Further improvement is achieved by inserting an AlN IL between GaN BL and AlGaN TL. However, experimental results also show that a HT AlN IL leads to relatively rough surfaces on AlGaN TLs, and an AlN IL changes the strain in the AlGaN TL from tensile to compressive type. In addition, an AlN BL improves the top surface quality of heterostructures. © 2007 American Institute of Physics. DOI: 10.1063/1.2747216