Growth of GaN on sapphire substrates using novel buffer layers of ECR-plasma-sputtered Al2O3/graded-AlON/AlN/Al2O3

We proposed and demonstrated GaN growth on sapphire substrates by metalorganic vapor phase epitaxy using novel buffer layers of Al2O3/graded-AlON/AlN/Al2O3. The buffer layers were deposited by electron cyclotron resonance plasma sputtering at room temperature. The total thickness of the buffer layers was around 20 nm. The cross-sectional bright-field transmission electron microscope observation showed that the dislocations were bent at the initial stage of the growth, indicating the enhancement of lateral growth. Typical dislocation density in the GaN layer was 6.5×108 cm−2. We obtained high electron mobility of 640 cm2/Vs at the electron concentration of 2.0×1017 cm−3 for Si-doped GaN. We also obtained high electron mobility of 1760 cm2/Vs at a sheet electron concentration of 8.3×1012 cm−2 for an AlGaN/GaN heterostructure. These results indicate that the quality of the epitaxial layer grown on sapphire substrates using the electron cyclotron resonance plasma sputtered buffer is comparable or superior to that of GaN layers using the conventional low-temperature buffer layer.