Microstructure of InN quantum dots grown on AlN buffer layers by metal organic vapor phase epitaxy

InN quantum dots (QDs) were grown over 2 in. Si (1 1 1) wafers with a 300 nm thick AlN buffer layer by atmospheric-pressure metal organic vapor phase epitaxy. When the growth temperature increased from 450 to 625 °C, the corresponding InN QDs height increased from 16 to 108 nm while the density of the InN QDs decreased from 1.6× 109 cm-2 to 3.3× 108 cm-2. Transmission electron microscopy showed the presence of a 2 nm thick wetting layer between the AlN buffer layer and InN QDs. The growth mechanism was determined to be the Stranski-Krastanov mode. The presence of misfit dislocations in the QDs indicated that residual strain was introduced during InN QDs formation. From x-ray diffraction analysis, when the height of the InN QDs increased from 16 to 62 nm, the residual strain in InN QDs reduced from 0.45% to 0.22%. The residual strain remained at 0.22% for larger heights most likely due to plastic relaxation in the QDs. The critical height of the InN QDs for releasing the strain was determined to be 62 nm.